Abstract
Background
Dual chamber pacing or single chamber atrial pacing ('physiologic' pacing) is believed to have an advantage over single chamber ventricular pacing in that it resembles cardiac physiology more closely by maintaining atrioventricular (AV) synchrony and dominance of the sinus node, which in turn may reduce cardiovascular morbidity and mortality thus contributing to patient survival and quality of life. However, a significant proportion of pacemakers currently implanted are single chamber ventricular pacemakers.
Objectives
The objective of this review was to assess the short‐ and long‐term clinical effectiveness of dual chamber pacemakers compared to single chamber ventricular pacemakers in adults with AV block, sick sinus syndrome or both. An additional objective was to assess separately any potential differences in effectiveness between dual chamber pacing and single chamber atrial pacing. The clinical effectiveness of single chamber atrial pacing versus single chamber ventricular pacing was not examined.
Search methods
The Cochrane Controlled Trials Register (The Cochrane Library Issue 3, 2002), MEDLINE (1966 to 2002), EMBASE (1980 to 2002) and the Science Citation Index (1980 to 2002) were searched on 19th August 2002. Citation lists and web sites were checked and researchers in the field contacted.
Selection criteria
Parallel group or crossover randomised controlled trials of at least 48 hours duration comparing dual chamber pacing and single chamber ventricular pacing, and investigating cardiovascular morbidity, mortality, patient related quality of life, exercise capacity and complication rates.
Data collection and analysis
Data was extracted onto pre‐piloted data extraction forms. Quality assessment was undertaken using a checklist, with a sub‐sample of quality data independently extracted by a second reviewer. Where appropriate data was available, meta‐analysis was performed. Where meta‐analysis was not possible, the number of studies showing a positive, neutral or negative direction of effect and statistical significance were simply counted.
Main results
Five parallel and 26 crossover randomised controlled trials were identified. The quality of reporting was found to be poor. Pooled data from parallel studies shows a statistically non‐significant preference for physiologic pacing (primarily dual chamber pacing) for the prevention of stroke, heart failure and mortality, and a statistically significant beneficial effect regarding the prevention of atrial fibrillation (odds ratio (OR) 0.79, 95% CI 0.68 to 0.93). Both parallel and crossover studies favour dual chamber pacing with regard to pacemaker syndrome (parallel: Peto OR 0.11, 95% CI 0.08 to 0.14; crossover: standardised mean difference (SMD) ‐0.74, 95% CI ‐ 0.95 to ‐0.52). Pooled data from crossover studies shows a statistically significant trend towards dual chamber pacing being more favourable in terms of exercise capacity (SMD ‐0.24, 95% CI ‐0.03 to ‐0.45). No individual studies reported a significantly more favourable outcome with single chamber ventricular pacing.
Authors' conclusions
This review shows a trend towards greater effectiveness with dual chamber pacing compared to single chamber ventricular pacing, which supports the current British Pacing and Electrophysiology Group's Guidelines regarding atrioventricular block. Additional randomised controlled trial evidence from ongoing trials in this area will further inform the debate.
Plain language summary
Compared to single chamber ventricular pacemakers, dual chamber pacemakers may reduce the incidence of complications in people with sick sinus syndrome and atrioventricular block
Sick sinus syndrome (SSS) and atrioventricular block (AV block) are the two most common reasons people have pacemakers implanted. Both involve the heart beating abnormally slowly. Pacemakers replace or control the heart's own electrical activity. Single chamber pacemakers work on one of the chambers (sections) of the heart, while dual chamber pacemakers, which are more expensive, work on two simultaneously. The review of trials found that dual chamber pacemakers tended to prevent more subsequent heart problems than single chamber ventricular pacemakers. The impact on people's overall quality of life is uncertain. The review did not investigate the relative benefits or risks of surgery to upgrade to a dual chamber pacemaker.
Background
Cardiac bradyarrhythmia (slow heart rhythm) results from the disturbance of the generation or conduction of cardiac electrical activity. Sick sinus syndrome (SSS) refers to a spectrum of cardiac arrhythmias that includes sinus arrest, sinoatrial block, sinus bradycardia or alternating paroxysmal atrial tachyarrhythmias with bradycardia (tachy‐brady syndrome). Patients can develop symptoms such as syncope, lightheadedness or dyspnoea during episodes of bradycardia, while patients with the tachy‐brady syndrome may develop atrial fibrillation (Gregoratos 1999). Atrioventricular block (AV block) refers to abnormalities in AV conduction and is classified as first, second (type I or II) or third degree (complete) block. Complete heart block is defined as the absence of all atrioventricular conduction. Patients may be asymptomatic or they may experience symptoms due to bradycardia and/or ventricular arrhythmia. (Gregoratos 1998; Julian 1992).
SSS and AV block are the major indications for pacemaker implantation in the US and other parts of the world (Tang 2000). Sick sinus syndrome accounts for approximately half of all pacemaker implants in industrialised countries and atrioventricular block for the majority of the remaining cases (Lamas 1997). These two indications accounted for around 70% of UK pacemaker implants in 1999 (NPD 2000).
Single chamber pacemakers sense and pace either in the atrium or the ventricle, while dual chamber pacemakers can sense/pace in both chambers. The atrial or ventricular output can be either inhibited or triggered in response to a sensed signal. Rate responsive pacemakers have one or more sensors that detect physical activity and adjust the pacing rate accordingly, which is necessary in patients with chronotropic incompetence (Bush 1994; Clarke 1991). The North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG) set up the NBG code (NASPE/BPEG Generic Code) in 1987 to describe different pacing modes (Bernstein 1987). In view of evolving technology this code has recently been updated (Bernstein 2002). See Additional Table 1 for a Glossary of Terms and See Table 2 for details of the revised NBG code.
1. Glossary.
| Term or abbreviation | Description |
| A | Atrium |
| V | Ventricle |
| D | Dual (atrium and ventricle) |
| I | Inhibited: a type of pacemaker response in which the output pulse is suppressed (or inhibited) when an intrinsic event is sensed |
| R | Rate modulation: the ability of pacemakers to increase the pacing rate in response to physical activity or metabolic demand |
| Sensing | Refers to the detection of spontaneous cardiac depolarisations |
| Tracking | A dual‐chamber pacing function in which atrial activity is sensed and results in a paced ventricular response after a predefined delay (the AV interval) |
| Physiological mode | Single chamber atrial pacing and dual chamber pacing are often referred to as 'physiological modes' as they more closely mimic normal cardiac physiology (including AV synchrony) |
| AAI | Single chamber atrial pacing; one lead is positioned in the atrium; pacing and sensing occurs in the atrium; atrial pacing is inhibited by sensed spontaneous atrial depolarisations; no rate modulation or multi‐site pacing |
| AAIR | Single chamber atrial pacing as above but with rate modulation |
| VVI | Single chamber ventricular pacing; one lead is positioned in the ventricle; pacing and sensing occurs in the ventricle; ventricular pacing is inhibited by sensed spontaneous ventricular depolarisations; no rate modulation or multi‐site pacing; loss of AV synchrony may occur with this pacing mode; may be referred to as 'non‐physiological' pacing |
| VVIR | Single‐chamber ventricular pacing as above but with rate response |
| DDD | Dual chamber pacing; use of two leads, one in the atrium and one in the ventricle; pacing and sensing occurs in both the atrium and the ventricle; in the absence of intrinsic activity, both chambers are paced at the programmed base rate; normally inhibited by atrial or ventricular sensing, and with ventricular pacing triggered by atrial sensing; no rate modulation or multi‐site pacing |
| DDDR | Dual chamber as above but with rate modulation |
| DDI | Dual chamber pacing without atrial tracking |
| DDIR | Dual chamber pacing without atrial tracking, but with rate modulation |
| VDD | Ventricular pacing, triggered by atrial sensing, inhibited by ventricular sensing, no atrial pacing |
| AV synchrony | Normal sequence of atrial depolarisation and contraction followed by ventricular depolarisation and contraction; maintenance of this sequence results in optimal ventricular filling and cardiac output |
| Multi‐site pacing | Refers to additional stimulation sites:A: stimulation sites in each atrium, more than one stimulation site in either atrium, or any combination of the two; V: stimulation sites in each ventricle, more than one stimulation site in either ventricle, or any combination of the two;D: any combination of V and A |
| BPEG | British Pacing and Electrophysiology Group |
| NASPE | North American Society of Pacing and Electrophysiology |
| NBG | NASPE/BPEG Generic Code |
2. Revised NBG Code for Pacing Modes.
| Chamber being paced | Chamber being sensed | Response to sensing | Rate modulation | Multisite pacing |
| O=none | O=none | O=none | O=none | O=none |
| A=atrium | A=atrium | I=inhibited | R=rate modulation | A=atrium |
| V=ventricle | V=ventricle | T=triggered | V=ventricle | |
| D=dual (A + V) | D=dual (A + V) | D=dual (T + I) | D=dual (A + V) | |
| Manufacturers' designation only: S=single (A or V) | Manufacturers' designation only: S=single (A or V) | |||
| Foot note: "Multi site pacing" Refers to additional stimulation sites:A: stimulation sites in each atrium, more than one stimulation site in either atrium, or any combination of the two; V: stimulation sites in each ventricle, more than one stimulation site in either ventricle, or any combination of the two; |
The normal sequence of atrial depolarisation and contraction followed by ventricular depolarisation and contraction is termed atrioventricular (AV) synchrony. Maintenance of this sequence results in optimal ventricular filling and cardiac output (Connolly 1996). Atrioventricular asynchrony and retrograde atrial activation occur more frequently with ventricular ('non‐physiological') pacing modes and are prevented by single chamber atrial or dual chamber ('physiological') pacing modes, which allow dominance of the sinus node (when intact) and more closely mimic normal cardiac physiology (Ausubel 1985; Bush 1994; Connolly 1996; Heldman 1990; Kusumoto 1996; Tang 2000).
'Pacemaker syndrome' refers to a spectrum of symptoms such as (pre‐) syncope, dyspnoea, chest pain, palpitations and lethargy associated with loss of AV synchrony (Ausubel 1985; Travill 1992). The incidence of reported pacemaker syndrome in VVI(R) pacemaker recipients varies widely in the literature, with estimates ranging from 7 to 10 % up to 83% (Heldman 1990; Kusumoto 1996). Reasons for this variation include the lack of a standard definition for pacemaker syndrome and the fact that these types of symptoms are common in cardiac patients with or without pacemakers (Connolly 1996). In addition to preventing pacemaker syndrome, it has also been suggested that dual chamber pacemakers reduce the risk of atrial fibrillation, stroke and death, and that they enhance exercise capacity and quality of life compared to single chamber pacemakers (Connolly 1996; Gregoratos 1998).
The choice of pacing mode depends to some extent on the underlying indication for pacing. The British Pacing and Electrophysiology Group's 1991 guidelines (Clarke 1991) stipulate that patients with intact AV conduction should be paced in the atrium only, whilst the ventricle should be paced if there is actual or threatened AV block. A contraindication for dual chamber pacing is AV block with chronic atrial fibrillation.
An ageing UK population and an increasing survival rate after surgical correction of paediatric congenital heart disease are likely to increase the pacemaker implantation rate. In recent years, pacemaker therapy has been advocated for conditions such as hypertrophic cardiomyopathy, idiopathic dilated cardiomyopathy, the long QT syndrome and after cardiac transplantation. In addition to an overall increase of implants there has been a clear trend over the last 20 years in favour of more complex rate‐responsive and/or dual chamber systems (NPD 2000). More complex models of pacemaker can be up to twice the cost of simple models due to more expensive hardware, a longer implantation time and potentially additional follow‐up due to complications or reprogramming requirements (Clarke 1991; Gregoratos 1998).
World‐wide surveys performed in 1997 showed an increase in the pacemaker implantation rate since 1993 in the USA, with an increasing proportion of dual chamber pacemakers being implanted (Bernstein 2001); the survey of Asian Pacific, Middle Eastern, South American countries and Canada (Mond 2001) revealed large variations in the implantation rates of dual chamber and single chamber pacemakers, with more developed countries generally implanting a higher proportion of dual chamber pacemakers than developing countries. European implantation rates have increased between 1994 and 1999 (NPD 2000), with an increasing proportion of dual chamber pacemakers being implanted.
Objectives
To assess the short and long‐term effects (benefits and harm) of permanent dual chamber pacemakers compared separately to single chamber ventricular pacemakers and single chamber atrial pacemakers in adults with sick sinus syndrome, atrioventricular block, or both, on cardiovascular morbidity and mortality, quality of life, exercise capacity and complication rate. Although of clinical relevance, the review did not assess the evidence regarding the potential clinical benefit of single chamber atrial based pacing compared to single chamber ventricular pacing.
Methods
Criteria for considering studies for this review
Types of studies
Randomised controlled trials of either parallel group or crossover design comparing single chamber ventricular pacing with dual chamber pacing, or single chamber atrial pacing with dual chamber pacing. In the case of a crossover study, all patients have a dual chamber pacing system implanted which is subsequently programmed to a single chamber ventricular or dual chamber pacing mode. In a parallel group study, patients are randomised to receive either a single chamber or a dual chamber pacing system.
Only studies in which patients are paced for a minimum duration of 48 hours in one pacing mode were included as the review is concerned with clinical outcomes rather than acute haemodynamics. After running the search strategies outlined below, the shortest pacing time in one pacing mode amongst the included studies was found to be one week.
Types of participants
A patient population aged 18 or over, where greater than 50% in one single trial have sick sinus syndrome, AV block or both.
Types of interventions
Rate‐adaptive or non rate‐adaptive pacemakers capable of sensing and/or pacing in both the atrium and ventricle, i.e. dual chamber pacemakers (eg DDD, DDDR, DDI, DDIR, VDD, VDDR).
Comparisons Rate‐adaptive or non rate‐adaptive pacemakers capable of sensing and/or pacing in the ventricle i.e. single chamber ventricular pacemakers (eg VVI, VVIR), or single‐chamber atrial pacemakers (eg AAI, AAIR). Studies that compare more than one type of dual chamber or single chamber pacemaker have been included, provided that a single chamber ventricular mode is compared to a dual chamber mode as part of the study.
Types of outcome measures
Primary outcomes
Cardiovascular mortality or all‐cause mortality.
Cardiovascular morbidity: symptoms of pacemaker syndrome (as defined by the trialists), onset of atrial fibrillation, stroke or other thromboembolic events, heart failure.
As there is no standard definition of pacemaker syndrome, the assessment criteria defined by the authors have been listed for each study (Additional Table 3 for crossover studies and Additional Table 4 for parallel studies). Where several studies have included the same criteria the results for these have been summarised and compared directly (see meta‐analyses).
3. Pacemaker syndrome results crossover studies.
| Study | Assessment tool | Outcome measure | Single chamber | Dual chamber | Stat significance | Direction of effect | Comments |
| Avery et al., 1994 | Questionnaire on 11 symptoms based on Minnesota 'Living with heart failure' questionnaire re symptoms and ability to carry out daily tasks (0‐5 score), max score 55. Low score = good sense of well‐being. | Group mean (SD) for total symptom score | VVI 28 (10) | DDD/VDD 19 (5) | p<0.05 | Fewer symptoms of pacemaker syndrome and better ability to carry out daily tasks in DDD/VDD mode compared to VVI mode. | |
| Boon et al., 1987 | Questionnaire on 4 symptoms (shortness of breath, dizziness, fatigue, general well‐being) scored from 0‐10 on visual analogue scale. High score = good sense of well‐being; more severe symptoms. | Group median, interquartile range (IR) and full range (FR) for individual symptoms Shortness of breath Dizziness Fatigue General well‐being | VVI 2.21 IR 1.0‐4.10 FR 0‐9.62 0.32 IR 0‐1.0 FR 0‐9.87 0.28 IR 0.13‐4.77 FR 0‐9.74 9.52 IR 5.45‐9.81 FR 3.37‐9.74 | DDD 1.15 IR 0‐2.18 FR 0‐6 0.06 IR 0‐0.29 FR 0‐4.49 0.13 IR 0‐1.99 FR 0‐7.95 7.21 IR 8.65‐9.93 FR 5.38‐9.93 | p<0.05 p<0.05 p<0.05 p<0.05 | Fewer symptoms of pacemaker syndrome and higher level of well‐being in DDD mode compared to VVI mode. | Data estimated from graph |
| Capucci et al., 1993 | Questionnaire on 8 symptoms (shortness of breath at rest, shortness of breath on exercise, neck pulsation, palpitation, chest pain at rest, chest pain on exercises, fainting, dizziness) scored 1‐5 for frequency or degree of discomfort. 1=least discomfort. | Group mean (?) for total symptoms.NB: not clear whether SD calculated. No individual patient data. | VVIR 25.5 (5.4) | DDD 19.0 (3.1) DDDR 17.8 (1.8) | DDD versus VVIR p<0.01 DDDR versus VVIR p<0.01 | Fewer symptoms of pacemaker syndrome in DDD and DDDR mode compared to VVIR mode. | |
| Channon et al.,1994 | Questionnaire on 7 symptoms (breathlessness, pulsation in neck, dizziness, blackout, wheeze, fatigue, palpitation) scored from 0‐5 on visual analogue scale. (0=not at all, 5=very severe) | Group mean (SD) for total symptoms group means (SD) for dizziness fatigue breathlessness | VVI 9.4 (5.67) 1.73 (1.71) 2.13 (1.69) 3.00 (1.89) | DDD 4.73 (4.40) 0.47 (0.92) 1.20 (1.42) 1.80 (1.66) | p<0.006 p<0.007 p=0.01 p<0.03 | Fewer symptoms of pacemaker syndrome in DDD mode compared to VVI mode. | |
| Davis et al., 1985 | Davis et al., 1985 Daily symptom diaries on 10 symptoms (chest pain, chest discomfort, dizziness, blurred vision, palpitation, dyspnoea at rest, dyspnoea on exertion, disturbed sleep, pulsating sensation in neck, pulsating sensation in abdomen) | Group mean episodes per week chest pain and/or discomfort dizziness palpitation dyspnoea at rest dyspnoea on exertion no SD or SE stated | VVI 1.7 2.2 1.0 1.5 7.3 | VDD 1.5 0.8 1.0 0.2 2.2 | NS NS NS NS NS | Fewer episodes per week of 4 symptoms of pacemaker syndrome in VDD mode compared to VVI mode. One symptom of pacemaker syndrome occurred at equal frequency in both modes.Results not listed for all symptoms. | |
| Deharo et al., 1996 | 5 symptoms (sleep disturbance, chest pain, palpitation, dizziness, neck pulsations) scored 0‐3. 0=no symptoms, 3=very frequent symptoms | Group mean (SD) forSleep disturbanceChest painPalpitationDizzinessNeck pulsations | VVIR1.13 (1.46)0.5 (0.91)0.6 (1.3)0.53 (0.91)0.33 (0.72) | DDD1.3 (1.44)0.2 (0.56)0.33 (0.72)0.14 (0.52)0.2 (0.56) | NSNSNSNSNS | Lower overall symptom score for 4 symptoms (chest pain, palpitation, dizziness, neck pulsations) in DDD mode compared to VVIR mode. One higher overall symptom score in DDD mode compared to VVI mode (sleep disturbance). No statistical significance for any differences. | |
| Hargreaves et al., 1995 | Questionnaire on frequency and severity of 8 symptoms (breathlessness pulsation, dizziness, blackout, wheeze, fatigue, palpitation, cough) scored 0‐5 each on analogue scale. (0=none, 5=very severe) | Group mean (SE) Means (SE) for groups according to pacing order: DDD/VVIRMeans (SE) for groups according to pacing order: VVIR/DDD | VVIR5.2 (0.8) 6.3 (1.0)2.7 (2.0) | DDD2.9 (0.8) 2.9 (1.0)3.9 (1.0) | p<0.05p<0.05NS | Overall significantly lower score for 8 symptoms of pacemaker syndrome in DDD mode compared to VVIR mode.Difference not significant if paced in VVIR mode first. | |
| Heldman et al., 1990 | Questionnaire on presence and severity of 16 symptoms (shortness of breath, fatigue, dizziness, apprehension, cough, pulsations in neck/abdomen, orthopnea, headache, palpitation, chest pain, choking sensation, confusion, pedal edema, sensation of tachycardia, chest congestion, diaphoresis) scored 0‐10. 0=not present, 10=very severe. | Group mean(SD) for total and individual symptoms.Total symptoms Shortness of breathFatigueDizzinessApprehensionCoughPulsation in neck/abdomenOrthopneaHeadachePalpitationsChest PainChoking SensationConfusionPedal EdemaSensation of TachycardiaChest CongestionDiaphoresis | VVI29.0 (26.1)3.3 (3.1)4.8 (3.5)2.9 (3.6)3.0 (3.6)1.7 (2.5)2.0 (3.2)1.3 (2.5)1.3 (2.3)1.5 (3.0)1.4 (2.6)1.3 (2.9)0.9 (2.2)0.9 (2.3)1.1 (2.5)1.1 (1.9)0.7 (2.3) | DDD/DDI7.3 (12.4)0.8 (1.8)1.3 (2.3)0.8 (1.3)0.3 (0.8)0.4 (1.6)0.4 (1.1)0.3 (1.3)0.5 (0.9)0.5 (1.0)0.4 (1.2)0.3 (1.2)0.2 (0.6)0.3 (0.9)0.4 (1.4)0.5 (1.6)0.1 (0.2) | p<0.001p<0.001p<0.001p<0.001p<0.001p=0.001p=0.002p<0.02p<0.02p<0.04p<0.04p<0.04p<0.05NSNSNSNS | Lower symptom score in DDD/DDI mode compared to VVI mode for all 16 symptoms. Significant difference for 12 out of 16 symptoms. | |
| Kamalvand et al., 1997 | Questionnaire on 11 cardiovascular related symptoms, score 0‐84 (score >/= 25 indicative of pacemaker syndrome) | Group mean (SD) total symptom score | VVIR26.8 (15.3) | DDDR22.3 (12.2)MS DDDR21.2 (12.4) | MS DDDR versus VVIR (p=0.01) | Higher symptom score in VVIR mode compared to dual modes. | |
| Kenny et al., 1996 | Diary card on daily frequency of 3 symptoms (chest pain, dizziness, palpitation);Symptom score for 4 symptoms (chest pain, dizziness, palpitation, syncope) compared to previous crossover period (scale 1‐5, 1=much worse, 5=much improved) | Group mean (SD) for episodes per week PalpitationDizzinessChest PainNumber of patients with specific score: 12345 | VVI019.13 13.00 32302 | DDD(100) DDD(150)0.94 0.604.25 4.967.09 25.750 21 11 34 14 3 | VVI versus DDD (100) and DDD (150) for dizziness p<0.01 DDD (150) vs DDD (100) for chest pain p<0.01 VVI versus DDD (100) for chest pain p<0.02 | Highest number of episodes per week in DDD (150) compared to DDD (100) and VVI. Fewer episodes per week for dizziness in dual modes compared to VVI. Similar levels for palpitations (dual modes slightly higher). Number of patients improving on their symptom score compared to previous crossover period is slightly higher in DDD (150) mode compared to VVI mode and highest in DDD (100) mode. | Group means estimated from graph |
| Kristensson et al., 1985 | Questionnaire on frequency and severity of 9 symptoms (palpitation, dizziness, syncope, pulsation in neck, fluttering before eyes, chest pain at rest, chest pain on exercise, dyspnoea at rest, dyspnoea on exercise) based on visual analogue scale (0‐10). 0=no symptoms, 10=extreme symptoms.Total number of patients reporting symptoms. | Group means for individual symptoms PalpitationDizzinessSyncopePulsation in neckEye flutterChest pain at restChest pain on exerciseDyspnoea at restDyspnoea on exerciseTotal number of patients with symptoms in each group:PalpitationDizzinessSyncopePulsation in neckEye flutterChest pain at restChest pain on exerciseDyspnoea at restDyspnoea on exercise | VVI75.61 29.27 12.20 68.77 18.29 24.39 30.00 20.24 134.15 1712418898933 | VDD26.83 15.85 1.22 30.49 9.76 4.88 23.17 4.88 65.09 107111649125 | p<0.01NSNSp<0.05NS p<0.05NSNSp<0.001 | Lower symptom score in VDD mode compared to VVI mode for 9 symptoms of pacemaker syndrome. Difference is significant for 4 symptoms (palpitation, pulsation in neck, chest pain at rest and dyspnoea on exercise). Fewer patients with symptoms in VDD group (for 8 of the 9 symptoms). One more patient with chest pain on exercise in the VDD group compared to the VVI group. | Group means estimated from graph |
| Lau et al., 1994 (1) | Questionnaire on incidence and frequency of 6 symptoms (dyspnoea, palpitation, dizziness, chest pain, sleep disturbance, neck pulsations) scored 1‐5 (1=all of the time, 5=never) | Group mean for individual symptomsDyspnoeaPalpitationDizzinessChest painSleep disturbanceNeck pulsations | VVIR3.42 3.00 3.80 4.27 3.96 4.67 AAIR4.00 4.00 3.90 4.67 4.67 5.00 | DDDR3.42 4.30 4.30 4.60 4.25 5.00 | VVIR versus AAIR for palpitation p<0.05 VVIR versus DDDR for palpitation p<0.001 | Lower incidence of symptoms in DDDR and AAIR mode (for 5 out of 6 symptoms) compared to VVIR. | Data estimated from graph |
| Lau et al., 1994 (2) | Physical Malaise Inventory (41 items). Higher numerical score indicates less severe symptoms. Results given for pain, dyspnoea, temperature intolerance, epigastric pain and palpitation only. | Group mean for individual symptoms Pain Dyspnoea Temperature intolerance Epigastric pain Palpitation | VVIR 1.72 1.83 1.63 1.85 1.81 | DDD DDDR 1.55 1.89 1.85 2.00 1.63 1.91 1.93 1.99 1.84 1.98 | p<0.01 DDD versus DDD for pain; p<0.05 DDDR versus DDD and DDDR versus VVIR for dyspnoea; p<0.01 DDDR versus DDD and DDDR versus VVIR for temperature intolerance; p<0.05 DDDR versus VVIR for epigastric pain; p<0.05 & p< 0.01 DDDR versus VVIR & DDDR versus VVIR for palpitation | Significantly fewer symptoms in DDDR mode compared to VVIR mode and for DDDR compared to DDD mode for 4 of 5 symptoms. | Data estimated from graph |
| Linde‐Edelstam et al., 1992 | Questionnaire on 4 symptoms (breathlessness, dizziness, chest pain, palpitation) on visual analogue scale (increasing no of mm=progressive severity of symptroms) | Group mean (SD) individual symptom scoreBreathlessnessDizzinessChest painPalpitation | VVIR18.1 (14.3)15.2 (22.6)6.8 (8.9)6.3 (15.2) | DDD9.5 (8.5)4.8 (8.5)2.6 (2.5)2.8 (8.1) | p=0.02 p=0.04p=0.06 p=0.03 | Fewer symptoms of pacemaker syndrome (breathlessness, dizziness, chest pain, palpitation) in DDD mode than VVIR mode. | |
| Lukl et al., 1994 | Questionnaire consisting of 19 questions, 11 of which relate to cardiovascular symptoms, on 6 point scale (0=optimal state, 6=worst state) | Group mean (SD) individual symptom scoreSwollen anklesBreathlessness at restBreathlessness during physical exertionOverexertion during household choresFatigueInsomniaDizzy spellsTrouble with memory and concentrationTightness in chestPalpitationSweating | VVIR0.9 (1.3)0.6 (1.3)3.2 (1.5)2.6 (1.4)2.7 (1.5)1.7 (1.5)1.7 (1.6)0.6 (0.9)0.8 (1.3)3.2 (1.8)2.4 (1.8) | DDD1.0 (1.3)1.0 (1.3)2.2 (1.6)1.6 (1.3)1.7 (1.6)1.9 (1.7)0.3 (0.8)1.0 (1.2)1.3 (1.7)0.9 (1.2)1.3 (1.3) | NSNSp<0.02p<0.01p<0.02NS p<0.005NSNSp<0.005 p<0.005 | Significantly lower symptom score in DDD mode compared to VVIR mode for 6 out of 11 symptoms listed. | |
| Menozzi et al., 1990 | Questionnaire on 6 symptoms (palpitation, dizziness, pulsating sensation in neck or abdomen, shortness of breath at rest, shortness of breath on effort, chest pain) scored 1‐5 (1=slight and occasional,5=severe and almost persistent)NB: no SD for individual symptoms stated | Group mean individual symptom scorePalpitationDizzinessPulsating sensationShortness of breath (rest)Shortness of breath (effort)Chest pain | VVIR199149271 | DDD5201110 | p=0.04NSp=0.05NSp=0.02NS | Significantly lower scores in DDD compared to VVIR mode for 3 out of 6 symptoms. | |
| Mitsuoka et al., 1988 | 5 symptoms (general well‐being, shortness of breath, chest pain, dizziness, palpitation) scored 1‐5 compared to previous month (1=much worse, 5=much improved);weekly attack rates (chest pain, dizziness, palpitation) | Group mean (SD)General well‐beingShortness of breathChest painDizziness PalpitationAttacks/week group mean (SD)Chest painDizzinessPalpitation | VVI2.061.94 (0.85)3.06 (1.00)2.56 (0.51)2.44 (0.89)1.470.53.66 | DDD3.373.44 (0.73)2.87 (0.62)3.25 (0.45)3.25 (0.77)1.590.340.33 | p<0.01p<0.01NSp<0.01p<0.01NSNSNS | Significantly higher scores in DDD mode compared to VVI mode for 4/5 symptoms; higher symptom score for chest pain in DDD mode.Differences in attack rates not significant | |
| Oldroyd et al., 1991 | Questionnaire comprising 3 sets of 8 questions relating to dyspnoea, fatigue and mood disturbance, scored on 100mm visual analogue scale. Maximum score of 800. | Estimated group means (SD)DyspnoeaFatigueMood disturbance | VVIR153.12 (119.12)240.62 (196.00)106.94 (57.65) | DDD133.68 (111.44)170.14 (138.35)85.07 (65.33) | NSNSNS | Lower symptom score in DDD mode, although not statistically significant. | Data estimated from graph |
| Perrins et al., 1983 | Daily diary card of symptoms (cheat pain, dizziness, palpitation, syncope)Subjective symptom score at end of crossover period regarding improvement for chest pain, dizziness, shortness of breath, palpitation and general well‐being, scored 1‐5 (1=much worse, 5=much improved) | Group mean (SD) for weekly attack ratesChest painDizzinessPalpitationSyncopeGroup mean (SD) symptom scoreGeneral well‐beingShortness of breathSyncopeDizzinessPalpitationChest pain | VVI1.08 (1.30)2.49 (4.7)1.76 (2.86)01.72 (0.6)2.0 (0.91)3.02.3 (0.91)2.6 (0.69)2.9 (0.31) | VDD1.16 (2.01)1.45 (2.67)0.35 (1.22)03.54 (0.8)3.45 (0.8)3.03.5 (0.7)3.3 (0.67)3.1 (1.1) | NSNSp<0.05NSp<0.01p<0.01NSp<0.02p<0.05NS | Similar weekly attack rates in VVI and VDD mode for 3/4 symptoms; higher rate of attack in VVI mode for palpitation.Improved symptom scores for general well‐being, shortness of breath, dizziness and palpitation in VDD mode compared to VVI mode. No difference in symptom score for syncope and chest pain. | |
| Rediker et al., 1988 | Questionnaire assessing 5 symptoms (dizziness, weakness, fatigue, shortness of breath, palpitation), scored 1‐6 (1=all of the time, 6=none of the time) | Group mean (SD) symptom scoreFatigueShortness of breathPalpitation | VVI3.7 (1.2)4.5 (1.1)4.7 (1.5) | DDD4.3 (1.0)5.2 (0.8)5.8 (0.4) | p=0.046p=0.01p=0.006 | Significantly fewer symptoms in DDD mode compared to VVI mode. | No results stated for dizziness or weakness. |
| Saner & Fricker,1996 | Questionnaire on incidence and frequency of symptoms heart failure and pacemaker syndrome (shortness of breath, palpitation, chest pain, dizziness) | Group mean (SD) total symptom score | VVIR5.7 (3.2) | DDD2.7 (1.6) | p=0.01 | Significantly fewer symptoms in DDD mode compared to VVIR mode. | |
| Sulke et al., 1994 | Questionnaire on 11 cardiovascular related symptoms, scored 0‐84 (score>25 indicative of pacemaker syndrome) | Group mean (SD) total symptom score | VVIR23.7 (9.8) | DDDR10.5 (5.5) | p=0.03 | Significantly fewer symptoms in DDD mode compared to VVIR mode. | |
| Sulke et al., 1992 | Questionnaire on 11 cardiovascular related symptoms, scored 0‐84 (score>25 indicative of pacemaker syndrome) | Group mean (SD) total symptom score | VVI10.45 | DDD DDI4.59 10.22 | p<0.05 for DDD compared to both other modes | Significantly lower symptom score in DDD mode compared to VVI and DDI modes. | Data estimated from graph. |
| Sulke et al., 1991 | Questionnaire assessing incidence and frequency of pacemaker syndrome symptoms (including shortness of breath, tiredness, neck flutter and lightheadedness), score 1‐5 (1=never, 5=all the time) | Group mean (SD) total symptom score | VVIR23.5 (11.5) | DDD DDDR DDIRmean score only stated: 14.4 (8.1) | p<0.01 for VVIR compared to mean of all dual modes | Significantly lower symptom score in dual compared to single mode. | |
| Yee et al., 1984 | Questionnaire assessing functional capacity and presence and frequency of symptoms (including angina, chest pain, dyspnoea, lightheadedness at rest and during exercise), 0=severe limitation in function, 60=absence of symptoms | Group mean (SD) symptom score | VVI50.1 (8.4) | VDD46.9 (8.9) | NS | Similar symptom scores in VDD and VVI modes |
4. Results parallel studies.
| Study | Outcome measure | Single chamber | Dual chamber | Stat significance | Comments |
| CTOPP (Connolly et al., 2000, Canada) | Annual rate of death from all causes (%) Annual rate of stroke or death due to cardiovascular causes combined (%) Annual rate atrial fibrillation (%) Annual rate of stroke (%) Annual rate of heart failure (%) | 'Ventricular' 6.6 (97/1474) 5.5 (81/1474) 6.6 (97/1474) 1.1 (16/1474) 3.5 (52/1474) | 'Physiologic' 6.3 (69/1094) 4.9 (54/1094) 5.3 (58/1094) 1.0 (11/1094) 3.1 (34/1094) | p=0.34 p=0.33 p=0.05 NS p=0.52 | |
| PASE (Lamas et al., 1998, USA) | n/N cases all‐cause mortality (total) SSS group AV block group n/N cases pacemaker syndrome n/N cases atrial fibrillation SSS group AV block group n/N cases stroke SSS group AV block group n/N cases heart failure SSS group AV block group | VVIR 34/204 17/85 15/102 53/204 33/204 24/85 11/102 5/204 2/85 3/102 17/204 7/85 9/102 | DDDR 32/203 11/90 17/99 0/203 35/203 17/90 16/99 3/203 1/90 1/99 9/203 6/90 3/99 | p=0.95 p=0.09 p=0.41 p<0.0001 p=0.8 p=0.06 p=0.26 NS NS NS NS NS NS | Assessment of pacemaker syndrome: 'symptoms of pacemaker syndrome severe enough to warrant reprogramming; multiple symptoms recorded in each patient (fatigue in all, dyspnoea or effort intolerance in 67%, orthopnoea or paroxysmal nocturnal dyspnoea in 24%, presyncope in 33% and a feeling of fullness in 20%); no scores calculated.' |
| MOST (Lamas et al., 2002, USA) | n/N cases all‐cause mortality n/N cases cardiovascular mortality n/N cases atrial fibrillation n/N cases pacemaker syndrome n/N cases stroke n/N cases heart failure | VVIR 204/996 92/996 270/996 182/996 49/996 123/996 | DDDR 200/1014 86/1014 217/1014 0/1014 41/1014 104/1014 | p=0.95* p=0.64" p=0.87 p=0.37 p=0.008 p=0.004 NS NS p=0.36 p=0.33 p=0.13 p=0.02 for *unadjusted "adjusted hazard ratio | Diagnosis of pacemaker syndrome required signs and symptoms of elevated right‐sided or left‐sided filling pressures or hypotention with ventricular pacing. Additionally, some patients had symptoms of severe pacemaker syndrome requiring reprogramming (but did not fully meet the strict definition) ‐these patients have been included in the number of cases with pacemaker syndrome. |
| Mattioli et al., 1998, Italy | % freedom from atrial fibrillation n/N cases of stroke | VVI, VVIR higher incidence of AF in total population in ventricular mode (no data available) higher incidence of AF in SSS population in ventricular modes (7% at 12 months, 20% at 24 months, estimated from graph) 19/105 | DDD, VDD, AAI lower incidence of AF in total population in ventricular mode (no data available) lower incidence of AF in SSS population in physiologic modes (0% at 12 months, 3.5% at 24 months, estimated from graph) 10/105 | p<0.05 p<0.05 p<0.05 | |
| Wharton et al., 1998, USA | % mortality % of population with pacemaker syndrome | VVIR 6.8 (6/98) 28% (27/98) | DDDR 3.2 (3/100) 0% (0/100) | p=0.007 p<0.0001 | Details on assessment of pacemaker syndrome not given. |
Secondary outcomes
Quality of life (assessment to include: measurement of psychological/mental functioning, social functioning, physical status including ability to undertake everyday activities, symptoms caused by disease or treatment).
Exercise assessment (a measurement of exercise duration and/or walking distance).
Complication rate (including device complications severe enough to warrant an additional visit to hospital, prolongation of a hospital stay, re‐implantation of the pacemaker or other surgical procedure).
Search methods for identification of studies
Electronic searches
A formal search strategy was developed using validated search filters for identifying randomised controlled trials combined with MeSH and text words relating to the intervention and comparator. Electronic searches of the Cochrane Library Controlled Clinical Trials Register (The Cochrane Library Issue 3, 2002) see Appendix 1, MEDLINE (1966 to 2002) see Appendix 2, EMBASE (1980 to 2002) see Appendix 3, SCIENCE CITATION INDEX (1980 to 2002) were undertaken on 19th August 2002, see Appendix 4.
No language restrictions were applied.
Searching other resources
Citation lists of included studies and reviews were searched and the trial co‐ordinators of identified ongoing trials were contacted. The web sites of professional associations (e.g. the British Pacing and Electrophysiology Group, the North American Society of Pacing and Electrophysiology, the American College of Cardiology and the American Heart Association), patient groups and manufacturers were searched using appropriate search terms.
In order to identify ongoing research, the following data sources were searched: National Research Registry, MRC funded projects, UK Department of Health Research, British Heart Foundation, clinicaltrials.gov/ct/gui/c/b, www.controlled‐trials.com, www.CentreWatch.com.
Data collection and analysis
Quality assessment strategy
A modified Jadad scale (Jadad 1996) was used for quality assessment of both parallel and crossover studies. Items assessed were method of randomisation, concealment, blinding (of participants and outcome assessors), completeness and evidence of intention to treat analysis. Additional quality items assessed for parallel studies were mode or device randomisation, comparability of study arms at the beginning of the trial and comparability of treatment of both study arms throughout the trial (e.g. in terms of care received, length of follow‐up etc.). For crossover studies, the presence of a washout period between treatments and a period effect test were thought to be important additional quality issues, as treatment received in the first crossover period can influence the effect of treatment in the second period and vice versa. (Hills 1979)
Studies were ranked according to quality in order to assess the feasibility of performing sensitivity analyses of the clinical effectiveness results. A study was judged to be of inadequate quality if there was evidence of failure to meet two or more quality criteria.
Data extraction strategy
All identified studies were assessed against the inclusion and exclusion criteria (JD). A random sample of identified studies was independently assessed (AFS) and any disagreement resolved through discussion with a third reviewer (RT).
A data extraction proforma was used to extract data on study characteristics, study quality and results (JD). The proforma was piloted on a sample of primary studies and modified before use. A subsample of quality data was independently extracted by a second reviewer (RT). Where data was available only in abstract form, or it was not evident from the full publication whether the inclusion criteria applied, the authors were contacted. Authors were also contacted for additional information on planned or ongoing trials.
Data synthesis
For crossover trials, data was generally presented in aggregate form for both crossover periods. We initially used a vote counting approach to quantify the results across all studies. In addition, we used MetaView 4.1 to perform meta‐analyses where appropriate outcome data were available. Fixed effects pooling was used throughout as there was no evidence of statistical heterogeneity. Odds ratios (with 95% confidence intervals) were calculated for binary data and standardised mean differences (SMD, with 95% confidence intervals) for continuous data. Funnel plots were generated, where possible to assess heterogeneity and possible publication bias (Egger 1998).
Results
Description of studies
A total of 1170 citations were originally retrieved of which 944 were judged to be clearly not relevant. The remaining 226 studies appeared to be comparisons of dual chamber pacing versus single chamber ventricular pacing. Of these, a further 194 studies were excluded as they did not meet one or more of the inclusion criteria. Of the remaining 32 studies, two reported different outcome measures of the same trial (Linde‐Edelstam 1992).
Of the 31 included randomised controlled trials, five were of parallel design and 26 of crossover design. There were differences between studies regarding modes compared, type of randomisation (mode or device) and population characteristics. All crossover studies necessarily used mode randomisation whilst three of the parallel studies used mode and two used device randomisation. In the parallel group studies, implantation occurred immediately before the study, whilst in crossover studies, patients were found to have been paced for varying time periods before the reprogramming of pacemakers for the study. Additional Table 5 and Table 6 list the main study characteristics of all included parallel and crossover studies.
5. Main study characteristics parallel studies.
| Study | Pacing indication | No of patients (m/f) | Age (mean) | Intervention | Comparator | Randomisation method | Study duration | Outcomes |
| CTOPP (Connolly et al., 2000, Canada) | SSS or AV block or both | 2568 (60% male, 40% female) | 73 +/‐10 | 'Physiological' pacemaker (dual or atrial, some rate‐adaptive); n=1094 | Ventricular pacemakers, some rate‐adaptive; n=1474 | Device | 36 months average (range 24‐60 months) | Atrial fibrillation, stroke, heart failure, mortality, complication rate |
| PASE (Lamas et al., 1998, USA) | SSS or AV block | 407 (60% male, 40% female) | 76 +/‐7 | DDDR; n=203 | VVIR; n=204 | Mode | 18.3 months average (range 7.2‐33.2 months) | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life |
| MOST (Lamas et al., 2002, USA) | SSS (21% also AV block) | 2010 (1045 male, 965 female) | median 74 | DDDR; n=1014 | VVIR; n=996 | Mode | median 33.1 months | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life, complication rate |
| Mattioli et al., 1998, Italy | SSS or AV block | 210 (113 male, 97 female) | 79 +/‐9 | 'Physiological' pacemaker (DDD, VDD, AAI); n=105 | VVI, VVIR; n=105 | Device | 24 months | Atrial fibrillation, stroke |
| Wharton et al., 1998, USA | SSS (with tachybrady syndrome) | 198 (109 male, 89 female) | median 72 | DDDR; n=100 | VVIR; n=98 | Mode | 23.7 months median | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life |
6. Main study characteristics crossover studies.
| Study | Pacing indication | No of patients (m/f) | Age (mean/range) | Intervention | Comparator | Randomisation | Study duration | Outcomes |
| Avery et al., 1994, UK | AV block | 13 (7 male, 6 female) | 79.4 | DDD | VVI | Mode | 1 month | Pacemaker syndrome, exercise capacity |
| Boon et al., 1987, UK | AV block or SSS | 15 (13 male, 2 female) | 69 (54‐81) | DDD | VVI | Mode | 4 weeks | Pacemaker syndrome |
| Capucci et al., 1993, Italy | AV block or SSS or both | 14 (12 male, 2 female) | 66.5 +/‐5 | DDD, DDDR | VVI | Mode | 1 month | Pacemaker syndrome, exercise capacity |
| Channon et al., 1994, UK | AV block | 16 (8 male, 8 female) | 81.25 (77‐88) | DDD | VVI | Mode | 7 days | Pacemaker syndrome, exercise capacity |
| Davis et al., 1985, Australia | AV block | 14 (10 male, 4 female) | 65 (23‐84) | VDD | VVI | Mode | 3 weeks | Pacemaker syndrome, exercise capacity |
| Deharo et al., 1996, France | AV block | 18 (14 male, 4 female) | 70 +/‐6.5 | DDD | VVIR | Mode | 1 month | Pacemaker syndrome, exercise capacity |
| Hargreaves et al., 1995, UK | AV block | 20 (14 male, 6 female) | 80.5 +/‐1 | DDD | VVIR | Mode | 2 weeks | Pacemaker syndrome, exercise capacity |
| Heldman et al., 1990, USA | AV block or SSS or both | 40 (23 male, 17 female) | 68 +/‐10 (47‐86) | DDD, DDI | VVI | Mode | 1 week | Pacemaker syndrome |
| Höijer et al., 2002, Sweden | AV block or SSS | 19 (13 male, 6 female) | 75.5 +/‐7.3 | DDDR, DDIR | VVI | Mode | 8 weeks | Quality of life |
| Kamalvand et al., 1997, UK | AV block, SSS or both | 48 (28 male, 20 female) | 64 +/‐13 | DDDR, DDDR with mode switching | VVIR | Mode | 4 weeks | Pacemaker syndrome, exercise capacity |
| Kenny et al., 1986, UK | AV block or SSS or both | 10 (4 male, 6 female) | 69.7 +/‐10.4 (52‐83) | DDD(100), DDD(150) | VVI | Mode | 1 month | Pacemaker syndrome |
| Kristensson et al., 1985, Sweden | AV block | 44 (22 male, 22 female) | 68 +/‐13 (18‐84) | VDD | VVI | Mode | 3 weeks | Pacemaker syndrome |
| Lau et al., 1994 (1), Hong Kong | SSS | 15 | 66+/‐2 | DDDR | AAIR, VVIR | Mode | 4 weeks | Pacemaker syndrome, quality of life |
| Lau et al., 1994 (2), Hong Kong | AV block or SSS | 33 | 66+/‐1 | DDD, DDDR | VVIR | Mode | 8 weeks | Pacemaker syndrome, quality of life |
| Linde‐Edelstam et al., 1992, Sweden | AV block | 17 (13 male, 4 female) | 64+/‐11 | DDD | VVIR | Mode | 2 months | Pacemaker syndrome, quality of life, exercise capacity |
| Lukl et al., 1994, Czech Republik | AV block or SSS | 21 | 68 +/‐8 | DDD | VVIR | Mode | 2 weeks | Pacemaker syndrome, quality of life |
| Menozzi et al., 1990, Italy | AV block | 14 (4 male, 10 female) | 72 +/‐6 | DDD | VVIR | Mode | 6 weeks | Pacemaker syndrome |
| Mitsuoka et al., 1988, UK | AV block or SSS | 16 (14 male, 2 female) | 64.1 +/‐12.2 (AV block); 63.3 +/‐ 13.1 (SSS) | DDD | VVI | Mode | 1 month | Pacemaker syndrome |
| Oldroyd et al., 1991, UK | AV block | 10 (7 male, 3 female) | 56 (32‐87) | DDD | VVIR | Mode | 1 month | Pacemaker syndrome, exercise capacity |
| Perrins et al., 1993, UK | AV block | 13 (9 male, 4 female) | 65 (32‐87) | VDD | VVI | Mode | 1 month | Pacemaker syndrome |
| Rediker et al., 1988, USA | AV block or SSS | 19 (15 male, 4 female) | 69.5 (35‐83) | DDD | VVI | Mode | 6 weeks | Pacemaker syndrome, exercise capacity |
| Saner & Fricker, 1996, Switzerland | AV block or SSS | 12 (7 male, 5 female) | 68 (36‐80) | DDD | VVIR | Mode | 6 weeks | Pacemaker syndrome, exercise capacity |
| Sulke et al., 1994, UK | AV block or AV block with SSS | 10 (6 male, 4 female) | 53 +/‐9.4 (42‐67) | DDDR | VVIR | Mode | 4 weeks | Pacemaker syndrome |
| Sulke et al., 1992, UK | AV block or AV block with SSS | 16 (11 male, 5 female) | 66.6 (41‐84) | DDD | VVI | Mode | 4 weeks | Pacemaker syndrome, exercise capacity |
| Sulke et al., 1991, UK | AV block or AV block with SSS | 22 (9 male, 13 female) | 51.9 (18‐81) | DDD, DDIR, DDDR | VVI | Mode | 4 weeks | Pacemaker syndrome, exercise capacity |
| Yee et al., 1984, Canada | AV block | 8 (4 male, 4 female) | 58.9 +/‐18.4 | VDD | VVI | Mode | 3 months | Pacemaker syndrome, exercise capacity |
All identified studies were comparisons of dual chamber pacing and single chamber ventricular pacing, or, in the case of two parallel studies, a combination of dual chamber and single chamber atrial pacing compared to single chamber ventricular pacing. No studies were identified that compared dual chamber pacing with single chamber atrial pacing.
The parallel studies had mean follow‐up times of 18.3 to 36 months and investigated pacemaker syndrome (three studies), atrial fibrillation (five studies), heart failure (four studies) and quality of life (three studies). Patient numbers varied between 198 and 2568. Crossover studies had smaller patient numbers (between 8 and 44) although with patients acting as their own controls numbers were effectively doubled. The study durations were shorter (between seven days and three months), and the outcomes investigated were subsequently restricted to short‐term ones (symptoms of pacemaker syndrome and/or exercise tests). Outcomes from parallel studies were reported as binary measures (e.g. presence or absence of pacemaker syndrome), whilst crossover studies used continuous measures (e.g. mean score from a questionnaire on symptom severity). The mean age of the patients taking part in the crossover studies (67.3 years) was lower than that of the patients in the parallel studies (73.7 years). There were differences between studies in the assessment of pacemaker syndrome (e.g. number and type of symptoms assessed and scoring scales).
Risk of bias in included studies
All studies failed to meet two or more quality criteria. There was a lack of details on: the process of randomisation (26/31 studies, 83.9%), concealment of allocation (29/31 studies, 93.5%), blinding of patients and/or outcome assessors (18/31 studies, 58.1%), withdrawals or crossovers (7/31 studies, 22.6%) and clear intention to treat analysis (23/31 studies, 74.2%). Details of the quality assessment are shown in Table 7 and Table 8. A period effect test was performed in only one of the crossover trials (Hargreaves 1995), and a washout period (two weeks) between treatments before symptom assessment was also only present in one crossover trial (Kristensson 1985). As the quality assessment was based solely on the published report, the lack of evidence of high quality may be a reflection of inadequate reporting rather than poor trial quality. As the checklist included items not contained within the Jadad checklist, particularly with regard to the crossover studies, a Jadad score was not calculated. As there were no clear differences in quality between studies, sensitivity analyses according to study quality were not performed.
7. Quality assessment parallel studies.
| Study | A | B | C | D | E | F | G | H | I |
| CTOPP (Connolly et al., 2000) | Y | X | X | X | X | X | X | Y | Single to dual: 2.1%, 2.7% and 4.3% at 1, 3 and 5 years; dual to single: 10.8%, 12.8% and 17.1% at 1, 3 and 5 years |
| PASE (Lamas et al., 1998) | Y | X | Y | X | X | Y | X | Y | Single to dual: 53/204; dual to single: 4/203 |
| MOST (Lamas et al., 2002) | Y | X | Y | X | Y | Y | X | Y | Single to dual: 313/996 (an additional 61crossed over from single to dual but crossed back to single); not stated for dual to single |
| Mattioli et al., 1998 | Y | X | X | X | X | Y | Y (n=7) | Y | Crossovers occurred but numbers not stated |
| Wharton et al., 1998 | Y | X | X | X | X | X | X | Y | Single to dual: 44%, dual to single 9% |
| A‐Trial described as randomised | |||||||||
| B‐Randomisation method stated | |||||||||
| C‐Adequate concealment described | |||||||||
| D‐Trial described as double‐blind | |||||||||
| E‐Statement regarding blinding of participants | |||||||||
| F‐Statement regarding blinding of outcome assessors | |||||||||
| G‐Withdrawals stated | |||||||||
| H‐Intention‐to‐treat analysis | |||||||||
| I‐Crossovers | |||||||||
| Y=criterion met | |||||||||
| X=criterion not met |
8. Quality assessment crossover studies.
| Study | A | B | C | D | E | F | G | H | I |
| Avery et al., 1994 | Y | X | X | Y | Y | Y | 3/13 | X | none |
| Boon et al., 1987 | Y | X | X | X | X | X | 3/18 | X | none |
| Capucci et al., 1993 | Y | Y | X | X | X | partly | 2/14 | X | none |
| Channon et al., 1994 | Y | X | X | Y | Y | Y | 2/16 | CT | 3/16 single to dual |
| Davis et al., 1985 | Y | X | X | Y | Y | partly | 0/13 | CT | none |
| Deharo et al., 1996 | Y | X | X | X | Y | X | 0/15 | CT | 1/15 single to dual |
| Hargreaves et al., 1995 | Y | X | X | Y | X | X | 0/20 | Y | 3/20 single to dual |
| Heldman et al., 1990 | Y | X | X | X | Y | X | 0/40 | CT | 17/42 single to dual |
| Höijer et al., 2002 | Y | X | X | Y | Y | Y | 0/19 | CT | 7/19 single to dual |
| Kamalvand et al., 1997 | Y | Y | X | Y | X | partly | 5/48 | X | 33% single to dual; 22% dual to single |
| Kenny et al., 1986 | Y | X | X | Y | Y | Y | 0/10 | CT | 2/10 single to dual |
| Kristensson et al., 1985 | Y | X | X | Y | Y | Y | 0/44 | CT | none |
| Lau et al., 1994 (1) | Y | X | X | Y | X | Y | 3/15 | X | 1/15 single to dual |
| Lau et al., 1994 (2) | Y | X | X | Y | X | Y | 0/33 | CT | 2/33 single to dual |
| Linde‐Edelstam et al., 1992 | Y | X | X | Y | Y | Y for exercise assessment, X for qol assessment | 2/17 (exercise assessment) | CT | 1/17 single to dual |
| Lukl et al., 1994 | Y | X | X | Y | Y | Y | 0/21 | Y | none |
| Menozzi et al., 1990 | Y | X | X | Y | Y | Y | 0/14 | CT | 5/14 single to dual |
| Mitsuoka et al., 1988 | Y | X | X | Y | Y | Y | 0/8 | CT | 2/16 single to dual |
| Oldroyd et al., 1991 | Y | X | X | Y | X | partly | 0/10 | CT | 1/10 single to dual |
| Perrins et al., 1983 | Y | X | X | Y | Y | Y | 0/13 | Y | none |
| Rediker et al., 1993 | Y | X | X | X | X | partly | 0/19 | X | single to dual unclear; none dual to single |
| Saner & Fricker, 1996 | Y | Y | X | X | X | X | 0/12 | CT | 4/12 single to dual |
| Sulke et al., 1994 | Y | X | X | Y | X | X | 0/10 | CT | 3/10 single to dual |
| Sulke et al., 1992 | Y | Y | X | Y | Y | Y | 0/16 | CT | unclear |
| Sulke et al., 1991 | Y | Y | X | Y | Y | Y | 0/22 | CT | 5/22 single to dual |
| Yee et al., 1984 | Y | X | X | X | Y | X | 0/8 | CT | none |
| A‐Study described as randomised | |||||||||
| B‐Randomisation method stated | |||||||||
| C‐Adequate concealment described | |||||||||
| D‐Trial described as double‐blind | |||||||||
| E‐Statement regarding blinding of participants | |||||||||
| F‐Statement regarding blinding of outcome assessors | |||||||||
| G‐Withdrawals | |||||||||
| H‐Intention‐to‐treat analysis | |||||||||
| I‐Crossover from one mode to another | |||||||||
| Y=criterion met | |||||||||
| X=criterion not met | |||||||||
| CT=can't tell |
Effects of interventions
Results from individual trials were pooled where the same outcome was measured and where the means and standard deviations were stated or calculable (for continuous outcomes) or the event rate for all patients stated (binary outcomes).
Cardiovascular mortality and morbidity ‐ parallel studies
For all cause mortality, stroke and heart failure, there was a trend towards a benefit from dual chamber pacing (all cause mortality, based on four studies: OR 0.94, 95% CI 0.80 to 1.12; stroke, based on four studies: OR 0.75, 95% CI 0.54 to 1.04; heart failure, based on three studies: OR 0.80, 95% CI 0.64 to 1.00). None of these differences were statistically significant.
The MOST (2002) trial only reported cardiovascular mortality. There was no significant difference between dual chamber pacing and single chamber ventricular pacing (unadjusted hazard ratio of 0.93, 95% CI 0.69 to 1.24; adjusted hazard ratio of 0.87, 95% CI 0.65 to 1.18).
The incidence of pacemaker syndrome was higher for patients paced in a ventricular mode compared to patients paced in a dual chamber mode. The pooled Peto odds ratio for symptoms of pacemaker syndrome, based on three studies, was OR 0.11 (95% CI 0.08 to 0.14). Based on four studies, the incidence of atrial fibrillation was also significantly higher in single chamber ventricular versus dual chamber pacemaker users (OR 0.79, 95% CI 0.68 to 0.93). Atrial fibrillation was measured as an outcome in one additional study, however, as no data was provided, these results could not be included in the meta‐analysis.
Subgroup analysis (SSS and AV block) of cardiovascular mortality and morbidity ‐ parallel studies
The composite outcome of stroke or death due to a cardiovascular cause was investigated in CTOPP (2000) where a statistically non‐significant trend for patients with SSS to benefit less from physiologic pacing compared to those with AV block was found.
For stroke, heart failure and mortality, the PASE (1998) trial found no significant differences between SSS and AV groups according to pacing mode. The incidence of atrial fibrillation in this trial was higher in a single chamber mode for SSS and higher in a dual chamber mode for AV block, however, these differences were not significant.
Mattioli (1998) found a significantly higher incidence of atrial fibrillation in a single chamber ventricular mode for the SSS group, however, data for the AV group was not reported.
Cardiovascular morbidity ‐ crossover studies
Due to the shorter duration of these studies, the only outcome relating to morbidity was incidence and frequency of symptoms of pacemaker syndrome, which was reported in 25 studies. In nine studies there were significantly fewer symptoms in a dual chamber mode and in four studies there were no significant differences between dual chamber or single chamber ventricular modes. In 12 studies, some of the symptoms measured appeared significantly less frequently in a dual chamber mode, whilst there were no significant differences for others. Pooling across nine studies, we found a statistically significant reduction in total pacemaker syndrome symptoms in dual chamber pacing compared to single chamber ventricular pacing of ‐0.74 SD units (95% CI ‐0.95 to ‐0.52). Means and standard deviations (SDs) were not available across all studies to allow their results to be included in this pooling. However, the direction of effect was consistent across all studies with either fewer symptoms in a dual chamber mode or no difference in symptoms between dual chamber and single chamber ventricular pacing.
We also found a statistically significant reduction in individual symptoms with dual chamber pacing, particularly with regard to dizziness, based on seven studies (SMD ‐0.89, 95% CI ‐1.13 to ‐0.64); fatigue, based on five studies (SMD ‐0.77, 95% CI ‐1.05 to ‐0.49); breathlessness, based on seven studies (SMD ‐0.92, 95% CI ‐1.18 to ‐0.66); palpitation, based on seven studies (SMD ‐0.69, 95% CI ‐0.93 to ‐0.45); and chest pain, based on five studies (SMD ‐0.33, 95% CI ‐0.60 to ‐0.05).
Subgroup analysis (SSS and AV block) of cardiovascular morbidity ‐ crossover studies
There were 12 crossover studies with an AV block population only and one study with an SSS population only, therefore, there was insufficient information to compare the results of these studies. Of the remaining studies, all but two reported data in an aggregate form for the subgroups. The remaining two studies (based on 8 and 21 patients in the SSS groups and 8 and 14 patients in the AV block groups respectively) showed little difference in effect between the two groups (Heldman; Mitsuoka).
Quality of life data
The PASE (1998) and MOST (2002) trials assessed quality of life using the SF‐36 index and the Specific Activity Scale respectively. No statistically significant difference in quality of life between single chamber ventricular and dual chamber modes was observed in the earlier study with the exception of mental health at 9 months and cardiovascular functional status at 18 months (benefit from dual chamber pacing). The 2002 study reported a statistically significant improvement in six out of eight SF‐36 subscales over a four year period with dual chamber pacing when last measurements were carried forward in those patients that crossed over. No significant differences were identified if the health status was carried over.
The PASE trial (1998) compared quality of life according to indication and pacing mode. There were no significant differences for any of the SF‐36 subscale scores in the AV block group, whilst in the SSS group there were significant differences favouring dual chamber pacing at three months in scores on the physical role, social function and emotional role subscales.
Five crossover studies investigated quality of life. The study by Höijer (2002) found an overall non‐significant preference for dual chamber pacing in 11 out of 17 quality of life functions measured, no difference between the two modes for four functions and a non‐significant preference for single chamber ventricular pacing for two functions. The other four crossover studies found either no significant difference between quality of life in a single chamber ventricular or dual chamber mode or a significantly higher quality of life in a dual chamber mode. No study found a statistically significant improvement in quality of life for patients paced with a single chamber ventricular mode regardless of which assessment tool was used. Given the range of measures used it was not possible to pool quality of life outcome across studies. Details of quality of life measurements can be found in the Additional Table 9. Results for studies investigating quality of life in different patient populations could not be compared as different assessment scales were used (Lau (1); Linde‐Edelstam 1992). One study (Lukl 1994) lists results for SSS (7 patients) and AV block (14 patients) groups separately, with little difference in quality of life between the groups.
9. Quality of life measurements.
| Study | Population size | Improved qol (dual)* | No difference (d/s)+ | Comment |
| PASE (Lamas et al., 1998, (parallel) | n = 407 | VVIR versus DDDR ‐mental health (SF‐36) at 9 months ‐cardiovascular functional status at 18 months | VVIR versus DDDR ‐8/8 SF‐36 items at 3 months ‐7/8 SF‐36 items at 9 months ‐7/8 SF‐36 items at 18 months ‐cardiovascular functional status at 3 and 9 months | SF‐36 (physical and social function, physical and emotional role, energy, pain, health perception, mental health) measured at 3, 9 and 18 months; cardiovascular functional status assessed using Specific Activities Scale at 3, 9 and 18 months |
| MOST (Lamas et al., 2002, parallel) | n = 2010 | VVIR versus DDDR ‐ 6/8 SF‐36 subscales at 48 months (when last measurement was carried forward in those patients who crossed over) | VVIR versus DDDR ‐2/8 SF‐36 subscales at 48 months ‐cardiovascular functional status at 48 months ‐time‐tradeoff utility at 48 months (when last measurement was carried forward in those patients who crossed over) | SF‐36 (physical and social function, physical and emotional role, energy, pain, health perception, mental health) measured at 48 months; cardiovascular functional status assessed using Specific Activities Scale at 48 months; time‐tradeoff utility measured at 48 months; if health status after crossover was included in the analysis, there were no significant differences between the groups |
| Höijer et al., 2002 (crossover) | n = 19 | VVIR versus DDDR/DDIR ‐1/4 items (cardiovascular symptomatology) ‐1/3 items (mood state) | VVIR versus DDDR/DDIR ‐3/4 items (cardiovascular symptomatology) ‐2/3 items (mood state) ‐2/2 items (sleep disturbance) ‐3/3 items (cognitive ability) ‐2/2 items (physical and social ability) ‐1/1 item (depressive feelings) ‐2/2 self‐perceived health | 7 sets of items assessed (cardiovascular symptomatology‐visual analogue scales, sleep disturbance‐visual analogue scale and sleep quality scale, cognitive functioning‐visual analogue scales, physical and social functioning‐5 point category scale, depressive feelings‐questionnaire, mood states‐4 point category scale, self‐perceived health status‐category scale) |
| Lau et al. ,1994 (1) (crossover) | n = 15 | VVIR versus DDDR ‐1/1 item (general well‐being) ‐1/6 items (incidence and frequency of symptoms) ‐1/11 items (psychologist's assessment) | VVIR versus DDDR ‐5/6 items (incidence and frequency of symptoms) ‐1/1 item (cardiovascular functional status) ‐10/11 items (psychologist's assessment) AAIR versus DDDR ‐1/1 item (general well‐being) ‐6/6 items (incidence and frequency of symptoms) ‐1/1 item (cardiovascular functional status) ‐11/11 items (psychologist's assessment) | DDDR, AAIR and VVIR modes compared. 4 sets of items assessed (general well‐being on visual analogue scale, incidence and frequency of symptoms, cardiovascular functional status using Specific Activities Scale, psychologist's assessment) |
| Lau et al. ,1994 (2) (crossover) | n = 33 | VVIR versus DDDR ‐4/5 items (physical malaise) ‐3/4 items (quality of life) ‐total sum for quality of life (based on 48 items) ‐4/5 items (illness perception) VVIR vs DDD ‐1/4 items quality of life ‐total sum for quality of life ‐1/5 items (illness perception) | VVIR vs DDDR ‐1/5 items (physical malaise) ‐1/4 items (quality of life) ‐1/5 items (illness perception) VVIR vs DDD ‐5/5 items physical malaise ‐3/4 items quality of life ‐4/5 items (illness perception) | DDDR, DDD and VVIR modes compared. 3 sets of items assessed (physical malaise using Physical Malaise Inventory, 41 items; quality of life based on 48 items; illness perception using Illness Perception Score, 43 items). Results only stated for certain items and overall for quality of life. |
| Linde‐Edelstam et al., 1992 (crossover) | n = 17 | VVIR versus DDD ‐4/4 items (cardiovascular symptomatology) ‐1/3 items (cognitive functioning) | VVIR versus DDD ‐2/2 items (sleep disturbance) ‐2/3 items (cognitive functioning) ‐2/2 items (physical and social functioning) ‐1/1 item (depressive score) ‐3/3 items mood states) ‐2/2 items (self‐perceived health status) | 7 sets of items assessed (cardiovascular symptomatology‐visual analogue scales, sleep disturbance‐visual analogue scale and sleep quality scale, cognitive functioning‐visual analogue scales, physical and social functioning‐5 point category scale, depressive feelings‐questionnaire, mood states‐4 point category scale, self‐perceived health status‐category scale) |
| Lukl et al., 1994 (crossover) | n = 21 | VVIR versus DDD ‐12/19 items | VVIR versus DDD ‐7/19 items | 19 questions on quality of life questionnaire, each question scored 0‐5 |
| * Statistically significant improvement in qol in a dual mode | + No statistically significant difference in qol between dual and single modes |
Exercise capacity
A total of 14 crossover studies reported exercise capacity. Six studies reported exercise capacity to be significantly higher for dual chamber pacing and five reported it to be similar in both dual chamber and single chamber ventricular pacing. Three studies, which compared more than two pacing modes, reported either higher exercise capacity or no difference depending on which dual chamber and single chamber modes were compared. No studies showed significantly increased exercise capacity with single chamber ventricular pacing.
Pooled study data based on 10 of these studies revealed a statistically significant increase in exercise capacity of 0.24 SD units (95% CI 0.03 to 0.45) with dual chamber pacing compared to single chamber ventricular pacing. A comparison of data according to SSS and AV block subgroups was not possible as data was presented only in an aggregate form.
Complication rates
We found no studies that assessed long‐term complications in the two pacing modes over the whole length of the trial period. The CTOPP trial (2000) reported a higher incidence of peri‐operative complications during dual chamber pacemaker implantation.
Publication bias
There was little evidence of funnel plot asymmetry for either total pacemaker symptoms (based on 8 crossover studies) or exercise capacity results (based on 10 crossover studies). This was confirmed with a non‐significant Egger test (p = 0.45 and p = 0.133 respectively).
Discussion
We identified a total of 5 parallel and 26 crossover randomised controlled trials that compared dual chamber pacing with single chamber ventricular pacing for AV block and SSS. Despite marked differences across studies in terms of pacing mode, population and outcome assessment, we observed a consistent trend towards benefit with dual chamber pacing compared to single chamber ventricular pacing across all studies and all outcomes. This benefit included a reduction in symptoms of pacemaker syndrome, atrial fibrillation and improvement in exercise capacity. This finding provides evidential support for the current British Pacing and Physiology Group guidelines (Clarke 1991), which recommend dual chamber pacing (DDD mode) as optimal therapy for atrioventricular (AV) block. In sick sinus syndrome the guidelines recommend single chamber atrial pacing. Whilst single chamber atrial pacing was not compared to single chamber ventricular pacing in this review, the review does support atrial based pacing for sick sinus syndrome.
It is recognised that there are additional complex variables which are likely to vary both between patients and studies. These include differences in AV delay in DDD/VDD mode, percentage of time paced and the presence of ventricular‐atrial asynchrony or retrograde conduction in VVI mode, all of which can impact on cardiac haemodynamics. A discussion of the likely impact of these factors is beyond the scope of this review.
The review did not assess the evidence for potential benefits of atrial versus ventricular pacing, nor was the potential difference in effectiveness between rate‐adaptive and non‐rate adaptive pacemakers investigated. At the time of completing the review, evidence had not been identified on the effectiveness of single chamber atrial compared to dual chamber pacing. One relevant trial has since been identified (see Nielsen, 2003, Studies Awaiting Assessment). The currently ongoing DANPACE study compares dual chamber pacing with single chamber atrial pacing in sick sinus syndrome and may provide further evidence. In order to inform the choice of the type of pacemaker for a given indication, the results of this review need to be considered in conjunction with these other pacing issues.
Although only randomised controlled trials were included in this review, poor quality trials may introduce bias and potentially overestimate the benefit of treatment. Given the consistent poor reporting of trial quality in this review we were unable to undertake a sensitivity analysis to examine the impact of quality on the conclusions of the review. Inevitably, any systematic review can be subject to publication bias, i.e., positive results and benefits are more likely to be published whilst side effects or treatment failures are under‐reported. To limit such bias we undertook extensive searching, moreover, we found no objective evidence of publication bias.
Authors' conclusions
Implications for practice.
On the basis of 5 parallel and 26 crossover randomised controlled trials, we observed some clinical benefit for dual chamber pacing compared to single chamber ventricular pacing. Pooled analysis demonstrated a significant reduction in atrial fibrillation and pacemaker syndrome with dual pacing.
There are a number of issues that impact on the applicability of the findings of this review to routine practice. Firstly, the mean age of the patients taking part in crossover studies (mean age 67.3 years) is lower than the mean age of those taking part in the parallel studies (mean age 73.7 years). It could be argued that younger patients, particularly those selected on the basis of their ability to take part in studies assessing exercise capacity, may be fitter or healthier than the general pacemaker population and, therefore, not representative. Second, the exercise tests undertaken in the trial setting may not necessarily be representative of the type of activities undertaken as part of daily life, and an improvement in an exercise test cannot necessarily be extrapolated to an improved ability to function in everyday life.
Randomisation by device (i.e. hardware) or mode (i.e. software) may have an influence on treatment effect. Mode randomisation is artificial in that patients randomised to a single chamber mode have a dual chamber device with an additional, unused lead implanted, which is then programmed to a single chamber mode. Any potential differences in complication rate or type between a single chamber and a dual chamber device would not manifest themselves in a trial using mode randomisation. There is also an argument that mode randomisation can lead to bias as the decision to upgrade from a single chamber to a dual chamber mode may be influenced by the ease with which this can be achieved. It can be seen from the included parallel studies that there was a trend for crossover rates to be higher in the mode randomised studies (MOST 2002 crossover rate: single to dual 26%, dual to single 2%; PASE 1998 crossover rate: single to dual: 31%, dual to single: not stated; Wharton 1998: crossover rate: single to dual 44%, dual to single 9%) than in the device randomised studies (CTOPP crossover rate: single to dual 2.1%, 2.7% and 4.3% at 1, 3 and 5 years; dual to single: 10.8%, 12.8% and 17.1% at 1, 3 and 5 years).
In contrast, device randomisation reflects everyday practice as patients receive the most appropriate device according to their condition. Here, the incidence of pacemaker syndrome may be underestimated as comparatively minor symptoms may not be thought worth the risk of upgrade. In summary, regardless of whether device or mode randomisation was undertaken, there are potential biases that need to be considered when interpreting the results of these trials.
Implications for research.
Further clinical evidence is needed particularly for the effect of dual chamber and single chamber ventricular pacing on patient related quality of life, long‐term adverse outcomes, mortality and the effect on patients with AV block and SSS respectively or other relevant indications. This is reflected by the four large randomised controlled trials that are currently ongoing or due to report in the UK (UKPACE, STOP‐AF), Denmark (DANPACE) and Canada (the extended CTOPP study). The Canadian trial referred to is a 3‐year extension of the CTOPP trial included in this review (Connolly 2000). The populations in these trials have AV block, SSS, or both, and physiologic pacemakers (dual chamber or single chamber atrial) are being compared to ventricular pacemakers, with the exception of the DANPACE study, which compares dual chamber pacing to single chamber atrial modes. Details of these trials are in the Table of Characteristics of Ongoing Studies. The design of any future trials should take into account the methodological issues raised in this report in order to avoid potentially biased results. Additionally, future trials should ensure that follow‐up is sufficient to identify long‐term effects of the different pacing modes. In the CTOPP trial, for example, the difference in effect on atrial fibrillation did not become apparent until after two years. Finally, there is newer evidence suggesting that right ventricular apical pacing, even in DDD pacing, may lead to interventricular desynchrony and subsequent haemodynamic deterioration (Tse 2002), which may explain a lack of strong evidence in favour of DDD pacing. This area is likely to become a focus of future research.
Feedback
Analyses following recommendations of the Handbook?, June 2013
Summary
Are your analyses of crossover studies in line with the recommendations of the Handbook? For example, in Analysis 6.1, it seems to us that you compare the same subjects while on the experimental condition and while on the control condition, as if they were different participants. This seems to be a serious error and your conclusions may be completely unfounded.
6.1. Analysis.
Comparison 6: Pacemaker syndrome crossover studies, Outcome 1: Pacemaker syndrome crossover studies
Nozomi Takeshima & Toshi A. Furukawa, Kyoto University School of Public Health.
Reply
The crossover analysis was based on the data available from the reported trials, and it is possible that this may give rise to a unit of analysis error. However, the Cochrane handbook states that “nevertheless, this incorrect analysis is conservative, in that studies are underweighted rather than over‐weighted.” Therefore it is unlikely that the consistent trend observed is a completely inaccurate reflection of study findings.
Janine Dretzke, lead author on the review Dual versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block.
Contributors
Nozomi Taeshima, Toshi A. Furukawa, and Janine Dretzke.
What's new
| Date | Event | Description |
|---|---|---|
| 15 April 2021 | Review declared as stable | This topic is considered a low priority for the portfolio of Cochrane Heart due to existing guideline recommendations. |
History
Protocol first published: Issue 3, 2002 Review first published: Issue 2, 2004
| Date | Event | Description |
|---|---|---|
| 25 June 2013 | Feedback has been incorporated | Query over analyses |
| 8 September 2008 | Amended | Converted to new review format. |
| 25 February 2004 | New citation required and conclusions have changed | Substantive amendment |
Acknowledgements
Chris Leonard and Rebecca Mason for administrative support.
Appendices
Appendix 1. Cochrane Controlled Trials Register (CCTR), search Aug 2002 Issue 3
1 Pacemaker‐artificial*:ME 2 Cardiac‐Pacing‐Artificial*:ME 3 Pacemaker* 4 Pacing 5 #1 or #2 or #3 or #4 6 Dual and Chamber 7 Dual and Pac* 8 Double and Chamber 9 Physiologic* and Pac* 10 Atrioventricular and Pac* 11 Atrioventricular and Sequential 12 Atrioventricular and Synchron* 13 DDD 14 DDDR 15 DDI 16 DDIR 17 VDD 18 VDDR 19 VDI 20 VDIR 21 #6 or #7 or #8 or #9 or #10 or #11 or #12 or #13 or #14 or #15 or #16 or #17 or #18 or #19 or #20 22 Single and Chamber 23 Single and Pac* 24 Atrial and Pac* 25 Ventricular and Pac* 26 VVI 27 VVIR 28 AAI 29 AAIR #22 or #23 or #24 or #25 or #26 or #27 or #28 or #29 #5 and #21 and #30
Appendix 2. MEDLINE (Ovid) search 1966 to Aug 2002
1 randomized controlled trial.pt. 2 controlled clinical trial.pt. 3 randomized controlled trials.sh. 4 random allocation.sh. 5 double‐blind method.sh. 6 single‐blind method.sh. 7 or/1‐6 8 (animal not human).sh. 9 7 not 8 10 clinical trial.pt. 11 exp clinical trials/ 12 (clin$ adj25 trial$).ti, ab. 13 ((singl$ or doubl$ or trebl$ or tripl$) adj5 (blind$ or mask$)).ti, ab. 14 placebos.sh. 15 placebo$.ti, ab. 16 random$.ti, ab. 17 research design.sh. 18 or/10‐17 19 18 not 8 20 19 not 9 21 comparative study.sh. 22 exp evaluation studies/ 23 follow up studies.sh. 24 prospective studies.sh. 25 (control$ or prospectiv$ or volunteer$).ti, ab. 26 or/21‐25 27 26 not 8 28 27 not (9 or 20) 29 9 or 20 or 28 30 exp pacemaker, artificial/ 31 exp cardiac pacing, artificial/ 32 pacemaker$.mp. 33 pacing.mp. 34 (dual adj chamber).mp. 35 (dual adj pac$).mp. 36 double adj chamber.mp. 37 physiologic$ adj pac$.mp. 38 (AV adj synchron$).mp. 39 (atrioventricular adj synchron$).mp. 40 (AV adj sequential).mp 41 (atrioventricular adj sequential).mp. 42 DDD.mp. 43 DDDR.mp. 44 DDI.mp. 45 DDIR.mp. 46 VDD.mp. 47 VDDR.mp. 48 VDI.mp. 49 VDIR.mp. 50 (single adj chamber).mp. 51 (single adj pac$).mp. 52 (atrial adj pac$).mp. 53 (ventricular adj pac$).mp. 54 VVI.mp. 55 VVIR.mp. 56 AAI.mp. 57 AAIR.mp. 58 or/30‐33 59 or/34‐39 60 or/50‐57 61 29 and 58 and 59 and 60
Appendix 3. EMBASE (Ovid) search, 1980 to Aug 2002
1 exp controlled trial/ 2 exp randomized controlled trial/ 3 exp clinical trial/ 4 exp controlled study/ 5 exp clinical study/ 6 exp prospective study/ 7 exp double blind procedure/ 8 exp crossover procedure/ 9 exp randomization/ 10 exp major clinical study/ 11 exp pacemaker/ 12 exp heart pacing/ 13 pacemaker$.mp. 14 pacing.mp. 15 (dual adj chamber).mp. 16 (dual adj pac$).mp 17 (double adj chamber).mp 18 (physiologic$ adj pac$).mp. 19 (atrioventricular adj synchron$).mp. 20 (AV adj synchron$).mp. 21 (atrioventricular adj sequential).mp. 22 (AV adj sequential).mp. 23 DDD.mp. 24 DDDR.mp. 25 DDI.mp. 26 DDIR.mp. 27 VDD.mp 28 VDDR.mp. 29 VDI.mp. 30 VDIR.mp. 31 (single adj chamber).mp. 32 (single adj pac$).mp 33 VVI.mp. 34 VVIR.mp. 35 AAI.mp. 36 AAIR.mp. 37 (atrial adj pac$).mp 38 (ventricular adj pac$).mp. 39 or/1‐10 40 or/11‐14 41 or/15‐30 42 or/31‐38 43 39 and 40 and 41 and 42
Appendix 4. Science Citation Index (Web of Science), 1980 to Aug 2002
(random* or blind* or comparative or comparison or prospective or controlled or trial or crossover or evaluation) and (pacemaker* or pacing) and (dual chamber or dual pac* or double chamber or DDD or DDDR or DDI or DDIR or VDD or VDDR or VDI or VDIR or physiologic* pac* or AV synchron* or atrioventricular synchron* or AV sequential or atrioventricualr sequential) and (single chamber or single pac* or atrial pac* or ventricular pac* or AAI or AAIR or VVI or VVIR)
Data and analyses
Comparison 1. Atrial fibrillation parallel studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1.1 Atrial fibrillation | 4 | 5183 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.79 [0.68, 0.93] |
1.1. Analysis.
Comparison 1: Atrial fibrillation parallel studies, Outcome 1: Atrial fibrillation
Comparison 2. All cause mortality parallel studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 2.1 All cause mortality | 4 | 5183 | Odds Ratio (M‐H, Random, 95% CI) | 0.94 [0.80, 1.12] |
2.1. Analysis.
Comparison 2: All cause mortality parallel studies, Outcome 1: All cause mortality
Comparison 3. Heart failure parallel studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3.1 Heart failure | 3 | 4985 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.80 [0.64, 1.00] |
3.1. Analysis.
Comparison 3: Heart failure parallel studies, Outcome 1: Heart failure
Comparison 4. Stroke parallel studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 4.1 Stroke | 4 | 5195 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.75 [0.54, 1.04] |
4.1. Analysis.
Comparison 4: Stroke parallel studies, Outcome 1: Stroke
Comparison 5. Pacemaker syndrome parallel studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 5.1 Pacemaker syndrome parallel studies | 3 | 2615 | Peto Odds Ratio (Peto, Fixed, 95% CI) | 0.11 [0.08, 0.14] |
5.1. Analysis.
Comparison 5: Pacemaker syndrome parallel studies, Outcome 1: Pacemaker syndrome parallel studies
Comparison 6. Pacemaker syndrome crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 6.1 Pacemaker syndrome crossover studies | 9 | 378 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.74 [‐0.95, ‐0.52] |
Comparison 7. Fatigue crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 7.1 Fatigue crossover studies | 5 | 212 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.77 [‐1.05, ‐0.49] |
7.1. Analysis.
Comparison 7: Fatigue crossover studies, Outcome 1: Fatigue crossover studies
Comparison 8. Dizziness crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 8.1 Dizziness crossover studies | 7 | 282 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.89 [‐1.13, ‐0.64] |
8.1. Analysis.
Comparison 8: Dizziness crossover studies, Outcome 1: Dizziness crossover studies
Comparison 9. Breathlessness crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 9.1 Breathlessness crossover studies | 7 | 262 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.92 [‐1.18, ‐0.66] |
9.1. Analysis.
Comparison 9: Breathlessness crossover studies, Outcome 1: Breathlessness crossover studies
Comparison 10. Palpitation crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 10.1 Palpitation crossover studies | 7 | 288 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.69 [‐0.93, ‐0.45] |
10.1. Analysis.
Comparison 10: Palpitation crossover studies, Outcome 1: Palpitation crossover studies
Comparison 11. Exercise capacity crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 11.1 Exercise capacity crossover studies | 10 | 356 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.24 [‐0.45, ‐0.03] |
11.1. Analysis.
Comparison 11: Exercise capacity crossover studies, Outcome 1: Exercise capacity crossover studies
Comparison 12. Chest pain crossover studies.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 12.1 Chest pain crossover studies | 5 | 208 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.33 [‐0.60, ‐0.05] |
12.1. Analysis.
Comparison 12: Chest pain crossover studies, Outcome 1: Chest pain crossover studies
Characteristics of studies
Characteristics of included studies [ordered by study ID]
Avery.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 13 patients (7 male, 6 female) with AV block, mean age 79.4 | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Boon.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 15 patients (13 male, 2 female) with AV block or SSS, mean age 69 (range 54‐81) | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Capucci.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 14 patients (12 male, 2 female) with AV block or SSS or both, mean age 66.5 (+/‐5) | |
| Interventions | DDD, DDDR versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Channon.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 16 patients (8 male, 8 female) with AV block, mean age 81.25 (range 77‐88) | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
CTOPP.
| Study characteristics | ||
| Methods | Parallel randomised controlled trial | |
| Participants | 2568 patients (60% male, 40% female) with SSS or AV block or both, mean age 73 (+/‐10) | |
| Interventions | 'Physiological' pacemaker (dual or atrial, some rate‐adaptive) versus single chamber ventricular pacemakers (some rate‐adaptive) | |
| Outcomes | Atrial fibrillation, stroke, heart failure, mortality, complication rate | |
| Notes | Device randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Davis.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 16 patients (8 male, 8 female) with AV block, mean age 65 (range 23‐84) | |
| Interventions | VDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Deharo.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 18 patients (14 male, 4 female) with AV block, mean age 70 (+/‐6.5) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Hargreaves.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 20 patients (14 male, 6 female) with AV block, mean age 80.5 (+/‐1) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Heldman.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 40 patients (23 male, 17 female) with AV block or SSS or both, mean age 68 (+/‐10, range 47‐86) | |
| Interventions | DDD, DDI versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Höijer.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 19 patients (13 male, 6 female) with AV block or SSS, mean age 75.5 (+/‐7.3) | |
| Interventions | DDDR, DDIR versus VVI | |
| Outcomes | Quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Kamalvand.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 48 patients (28 male, 20 female) with AV block or SSS or both, mean age 64 (+/‐13) | |
| Interventions | DDDR, DDDR with mode switching versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Kenny.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 10 patients (4 male, 6 female) with AV block or SSS or both, mean age 69.7 (+/‐10.4, range 52‐83) | |
| Interventions | DDD(100), DDD(150) versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Kristensson.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 44 patients (22 male, 22 female) with AV block, mean age 68 (+/‐13, range 18‐84) | |
| Interventions | VDD versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Lau (1).
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 15 patients (male/female not specified) with SSS, mean age 66 (+/‐2) | |
| Interventions | DDDR versus VVIR, AAIR | |
| Outcomes | Pacemaker syndrome, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Lau (2).
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 33 patients (male/female not specified) with AV block or SSS, mean age 66 (+/‐1) | |
| Interventions | DDD, DDDR versus VVIR | |
| Outcomes | Pacemaker syndrome, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Linde‐Edelstam.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 17 patients (13 male, 4 female) with AV block, mean age 64 (+/‐11) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Lukl.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 21 patients (male/female not specified) with AV block or SSS, mean age 68 (+/‐8) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Mattioli.
| Study characteristics | ||
| Methods | Parallel randomised controlled trial | |
| Participants | 210 patients (113 male, 97 female) with SSS or AV block, mean age 79 (+/‐9) | |
| Interventions | 'Physiological' pacemaker (DDD, VDD, AAI) versus VVI, VVIR | |
| Outcomes | Atrial fibrillation, stroke | |
| Notes | Device randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Menozzi.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 14 patients (4 male, 10 female) with AV block, mean age 72 (+/‐6) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Mitsuoka.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 16 patients (14 male, 2 female) with AV block or SSS, mean age 64.1 (+/‐12.2) AV block, 63.3 (+/‐13.1) SSS | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
MOST.
| Study characteristics | ||
| Methods | Parallel randomised controlled trial | |
| Participants | 2010 patients (1045 male, 965 female) with SSS (21% also AV block), median age 74 | |
| Interventions | DDDR versus VVIR | |
| Outcomes | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life, complication rate | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Low risk | A ‐ Adequate |
Oldroyd.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 10 patients (7 male, 3 female) with AV block, mean age 56 (range 32‐87) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
PASE.
| Study characteristics | ||
| Methods | Parallel randomised controlled trial | |
| Participants | 407 patients (60% male, 40% female) with SSS or AV block, mean age 76 (+/‐7) | |
| Interventions | DDDR versus VVIR | |
| Outcomes | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Low risk | A ‐ Adequate |
Perrins.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 13 patients (9 male, 4 female) with AV block, mean age 65 (range 32‐87) | |
| Interventions | VDD versus VVI | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Rediker.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 19 patients (15 male, 4 female) with AV block or SSS, mean age 69.5 (35‐83) | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Saner and Fricker.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 12 patients (7 male, 5 female) with AV block or SSS, mean age 68 (range 36‐80) | |
| Interventions | DDD versus VVIR | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Sulke 1991.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 22 patients (9 male, 13 female) with AV block or AV block with SSS, mean age 51.9 (range 18‐81) | |
| Interventions | DDD, DDIR, DDDR versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Sulke 1992.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 16 patients (11 male, 5 female) with AV block or AV block with SSS, mean age 66.6 (range 41‐84) | |
| Interventions | DDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Sulke 1994.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 10 patients (6 male, 4 female) with AV block or AV block with SSS, mean age 53 (+/‐9.4, range 42‐67) | |
| Interventions | DDDR verus VVIR | |
| Outcomes | Pacemaker syndrome | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Wharton.
| Study characteristics | ||
| Methods | Parallel randomised controlled trial | |
| Participants | 198 patients (109 male, 89 female) with SSS (with tachybrady syndrome), median age 72 | |
| Interventions | DDDR versus VVIR | |
| Outcomes | Pacemaker syndrome, atrial fibrillation, stroke, heart failure, mortality, quality of life | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Yee.
| Study characteristics | ||
| Methods | Crossover randomised controlled trial | |
| Participants | 8 patients (4 male, 4 female) with AV block, mean age 58.9 (+/‐18.4) | |
| Interventions | VDD versus VVI | |
| Outcomes | Pacemaker syndrome, exercise capacity | |
| Notes | Mode randomised | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Unclear risk | B ‐ Unclear |
Characteristics of excluded studies [ordered by study ID]
| Study | Reason for exclusion |
|---|---|
| Abe 1992 | Outcome assessed not relevant |
| Adinolfi 1985 | Outcome assessed not relevant |
| Aggarwal 1995 | Not a randomised controlled trial |
| Ahern 1992 | Not a randomised controlled trial |
| Alpert 1986 | Not a randomised controlled trial |
| Alpert 1987 | Not a randomised controlled trial |
| Amici 1996 | Outcome assessed not relevant |
| Azam 1998 | Outcome assessed not relevant |
| Baldo 1996 | Not a randomised controlled trial, outcome assessed not relevant |
| Barrington 1995 | Duration of study less than 48 hours |
| Batey 1990 | Duration of study less than 48 hours |
| Been 1984 | Outcome assessed not relevant |
| Blanc 1992 | Duration of study less than 48 hours, outcome assessed not relevant |
| Bosch 1990 | Not a randomised controlled trial, outcome assessed not relevant |
| Bren 1986 | Duration of study less than 48 hours |
| Brignole 1988 | Indication for pacing other than SSS or AV block |
| Brignole 1989a | Indication for pacing other than SSS or AV block |
| Brignole 1989b | Indication for pacing other than SSS or AV block |
| Brignole 1991 | Not a randomised controlled trial, indication for pacing other than SSS or AV block |
| Brignole 1992 | Indication for pacing other than SSS or AV block |
| Brunner‐La 2000 | Duration of study less than 48 hours |
| Cabello 1990 | Not a randomised controlled trial, outcome assessed not relevant |
| Cabello 1996 | Not a randomised controlled trial |
| Candinas 1994 | Duration of study less than 48 hours |
| Chabernaud 1993 | Duration of study less than 48 hours |
| Channon 1997 | 1st part of study less than 48 hours duration, 2nd part of study also reported in study included in this review (Channon et al., 1994) |
| Chauhan 1994 | Not a randomised controlled trial |
| Chida 1993 | Not a randomised controlled trial |
| Copperman 1993 | Outcome assessed not relevant |
| Daubert 1984 | Duration of study less than 48 hours, outcome assessed not relevant |
| Davies 1985 | Outcome assessed not relevant |
| DeFilippi 1981 | Outcome assessed not relevant |
| Douard 1995 | Duration of study less than 48 hours |
| Dritsas 1993 | Outcome assessed not relevant |
| Duan 2001 | Not a randomised controlled trial |
| Eagle 1988 | Not a randomised controlled trial |
| Ebagosti 1988 | Not a randomised controlled trial |
| Faerestrand 1985 | Outcome assessed not relevant |
| Fananapazir 1983a | Duration of study less than 48 hours |
| Fananapazir 1983b | Duration of study less than 48 hours |
| Faria 1991 | Not a randomised controlled trial, outcome assessed not relevant |
| Fishberger 1996 | Indication for pacing other than SSS or AV block. Pacing following surgery |
| French 1988 | Duration of study less than 48 hours |
| Frielingsdorf 1995 | Duration of study less than 48 hours |
| Fromer 1987 | Not a randomised controlled trial |
| Fukumoto 1986 | Duration of study less than 48 hours |
| Fukuoka 2000 | Not a randomised controlled trial, outcome assessed not relevant |
| Gallik 1994 | Duration of study less than 48 hours |
| Ghio 1991 | Outcome assessed not relevant |
| Gold 1995 | Indication for pacing other than SSS or AV block. |
| Gold 2000 | Indication for pacing other than SSS or AV block, outcome assessed not relevant |
| Griebenow 1984 | Indication for pacing other than SSS or AV block, outcome assessed not relevant |
| Griebenow 1989 | Indication for pacing other than SSS or AV block, outcome assessed not relevant |
| Hedman 1985 | Outcome assessed not relevant |
| Hedman 1988 | Outcome assessed not relevant |
| Hoeschen 1991 | Outcome assessed not relevant |
| Horie 1999 | Not a randomised controlled trial, outcome assessed not relevant |
| Ijiri 2000 | Duration of study less than 48 hours |
| Iliev 2000 | Outcome assessed not relevant |
| Ishikawa 1994 | Not a randomised controlled trial, outcome assessed not relevant |
| Ishikawa 1995 | Not a randomised controlled trial, outcome assessed not relevant |
| Ishikawa 1996 | Not a randomised controlled trial, outcome assessed not relevant |
| Iwase 1986 | Not a randomised controlled trial, outcome assessed not relevant |
| Iwase 1991 | Duration of study less than 48 hours |
| Jordaens 1988 | Unclear if inclusion criteria met, author contacted but no reply received |
| Jutzy 1990 | Duration of study less than 48 hours |
| Jutzy 1991 | Duration of study less than 48 hours |
| Jutzy 1992a | Not a randomised controlled trial |
| Jutzy 1992b | Duration of study less than 48 hours |
| Jutzy 1992c | Duration of study less than 48 hours, outcome assessed not relevant |
| Jutzy 1994 | Duration of study less than 48 hours |
| Kamalvand 1996 | Indication for pacing other than SSS or AV block. |
| Kano 1992 | Outcome assessed not relevant |
| Kargul 1996 | Not a randomised controlled trial, outcome assessed not relevant |
| Kikis 1983 | Not a randomised controlled trial, outcome assessed not relevant |
| Kolettis 1995 | Outcome assessed not relevant |
| Kolettis 1998 | Outcome assessed not relevant |
| Kolettis 2000 | Outcome assessed not relevant |
| Koller 1996a | Unclear if inclusion criteria met (regarding underlying indication), author contacted, no reply received |
| Koller 1996 b | Unclear if inclusion criteria met (regarding underlying indication), author contacted, no reply received |
| Kristensson 1983 | Duration of study less than 48 hours |
| Kristensson 1985 | Duration of study less than 48 hours |
| Kristensson 1986 | Outcome assessed not relevant |
| Kruse 1982 | Not a randomised controlled trial |
| Kyriakides 1994 | Not a randomised controlled trial, outcome assessed not relevant. Duration of study less than 48 hours |
| Labovitz 1985 | Not a randomised controlled trial, outcome assessed not relevant |
| Lamaison 1993 | Duration of study less than 48 hours |
| Lascault 1989 | Not a randomised controlled trial, outcome assessed not relevant |
| Lau 1990 | Duration of study less than 48 hours, outcome assessed not relevant |
| Lau 1992 | Not a randomised controlled trial |
| Lau 1997 | Outcome assessed not relevant |
| LaVilla 1994 | Not a randomised controlled trial, outcome assessed not relevant. Duration of study less than 48 hours |
| Leclercq 1995 | Duration of study less than 48 hours |
| Leclercq 1998 | Indication other than SSS or AV block, outcome assessed not relevant |
| Leman 1985 | Outcome assessed not relevant |
| Lemke 1990 | Outcome assessed not relevant |
| Linde‐Edelstam 1992 | Duration of study less than 48 hours |
| Lo 1993 | Not a randomised controlled trial, outcome assessed not relevant |
| Lo 1997 | Duration of study less than 48 hours, outcome assessed not relevant |
| Lotto 1985 | Outcome assessed not relevant |
| Love 1984 | Outcome assessed not relevant |
| Lukl 1991 | Duration of study less than 48 hours |
| Lukl 1992a | Not a randomised controlled trial |
| Lukl 1992b | Not a randomised controlled trial |
| Lukl 1994 | Duration of study less than 48 hours |
| Madigan 1984 | Indication other than SSS or AV block, outcome assessed not relevant. |
| Mahmud 1983 | Outcome assessed not relevant |
| Mahy 1996 | Outcome assessed not relevant |
| Maity 1987 | Duration of study less than 48 hours, outcome assessed not relevant |
| Maity 1992 | Duration of study less than 48 hours |
| Manolis 1998 | Outcome assessed not relevant |
| Manolis 2000 | Outcome assessed not relevant |
| Markewitz 1991 | Outcome assessed not relevant |
| Maron 1999 | Indication other than SSS or AV block |
| Martinelli 2000 | Not a randomised controlled trial |
| Maseki 1985 | Outcome assessed not relevant |
| Mattioli 1997 | Not a randomised controlled trial |
| Mattioli 1998 | Not a randomised controlled trial |
| Mattioli 1999 | Not a randomised controlled trial |
| McIntosh 1997 | Indication other than SSS or AV block |
| McMeekin 1990 | Not a randomised controlled trial |
| Meisel 2000 | Indication other than SSS or AV block |
| Mizutani 1997 | Duration of study less than 48 hours |
| Murphy 1997 | Indication other than SSS or AV block |
| Nielsen 2000 | Outcome assessed not relevant |
| Nielson 1985 | Duration of study less than 48 hours |
| Nishimura 1982 | Outcome assessed not relevant |
| Nishimura 1997 | Indication other than SSS or AV block |
| Nitsch 1983 | Not a randomised controlled trial, outcome assessed not relevant |
| Nitsch 1984a | Not a randomised controlled trial, outcome assessed not relevant |
| Nitsch 1984b | Not a randomised controlled trial, outcome assessed not relevant |
| Noll 1990 | Outcome assessed not relevant |
| Nordlander 1987 | VVI versus VAT modes compared, duration of study less than 48 hours |
| Nowak 1995 | Duration of study less than 48 hours |
| Occhetta 1997 | Duration of study less than 48 hours |
| Occhetta 1998 | Indication other than SSS or AV block |
| Oldroyd 1990 | Duplication (abstract only) of Oldroyd 1991 included in the review |
| Ovsyshcher 1992 | Not a randomised controlled trial, outcome assessed not relevant |
| Ovsyshcher 1993 | Outcome assessed not relevant |
| Papadopoulos 1997 | Duration of study less than 48 hours, outcome assessed not relevant |
| Payne 1995 | Outcome assessed not relevant |
| Payne 1996 | Not a randomised controlled trial, duration of study less than 48 hours |
| Payne 1997 | Not a randomised controlled trial, outcome assessed not relevant |
| Pearson 1989 | Outcome assessed not relevant |
| Pehrsson 1983 | Not a randomised controlled trial, outcome assessed not relevant |
| Pehrsson 1988 | Duration of study less than 48 hours |
| Perrins 1984 | Duration of study less than 48 hours |
| Proctor 1991 | Outcome assessed not relevant |
| Providencia 1988 | Not a randomised controlled trial |
| Reynolds 1983 | Outcome assessed not relevant |
| Rickli 2000 | Duration of study less than 48 hours |
| Ritter 1994 | Not a randomised controlled trial |
| Roelke 1994 | Not a randomised controlled trial |
| Romero 1981 | Outcome assessed not relevant |
| Romero 1984 | Not a randomised controlled trial, outcome assessed not relevant |
| Rosenqvist 1991 | Outcome assessed not relevant |
| Saccomamo 1995 | Not a randomised controlled trial |
| Saccomanno 1989 | Outcome assessed not relevant |
| Sack 1999 | Indication other than SSS or AV block, outcome assessed not relevant |
| Samoil 1993 | Indication other than SSS or AV block, outcome asssessed not relevant |
| Santini 1990 | Not a randomised controlled trial |
| Schofield 1986 | Duration of study less than 48 hours |
| Schwaab 1998 | Paper unobtainable |
| Sedney 1989 | Not a randomised controlled trial, outcome assessed not relevant |
| Shigemura 1990 | Outcome assessed not relevant |
| Simantirakis 1997 | Outcome assessed not relevant |
| Snoeck 1992 | Not a randomised controlled trial |
| Sparks 1999 | Outcome assessed not relevant |
| Sparks PB, Mond2 | Outcome assessed not relevant |
| Stangl 1988 | Outcome assessed not relevant |
| Stewart 1984 | Not a randomised controlled trial, outcome assessed not relevant |
| Stierle 1995 | Outcome assessed not relevant |
| Stojnic 1996 | Not a randomised controlled trial, outcome assessed not relevant |
| Stone 1982 | Not a randomised controlled trial |
| Sulke 1990 | Not a randomised controlled trial |
| Takeuchi 1990 | Not a randomised controlled trial |
| Tani 1992 | Duration of study less than 48 hours |
| Taylor 1996 | Duration of study less than 48 hours, outcome assessed not relevant |
| Theodorakis 1990 | Outcome assessed not relevant |
| Theodorakis 1992a | Outcome assessed not relevant |
| Theodorakis 1992b | Outcome assessed not relevant |
| Vardas 1996 | Outcome assessed not relevant |
| Vardas 1997a | Outcome assessed not relevant |
| Vardas 1997b | Duration of study less than 48 hours |
| Videen 1986 | Outcome assessed not relevant |
| Von 1984 | Outcome assessed not relevant |
| Wakakura 1992 | Outcome assessed not relevant |
| Whiting 1983 | Not a randomised controlled trial, outcome assessed not relevant |
| Yoshida 1999 | Not a randomised controlled trial, outcome assessed not relevant |
| Yoshitomi 1998 | Not a randomised controlled trial, outcome assessed not relevant |
Characteristics of ongoing studies [ordered by study ID]
CTOPP extended.
| Study name | Canadian Trial of Physiologic Pacing Investigators |
| Methods | |
| Participants | 2568 patients with SSS, AV block or both |
| Interventions | Physiological versus ventricular pacemakers |
| Outcomes | mortality and stroke; atrial fibrillation, heart failure, complication rate |
| Starting date | First part of trial completed; included in this review (Connolly 2000) |
| Contact information | S Connolly, Department of Medicine, McMaster University, Hamilton, Ontario, Canada |
| Notes | Follow‐up extended from 3‐6 years; additional data expected 2003 |
DANPACE.
| Study name | Danish multicentre study |
| Methods | |
| Participants | 1900 patients with SSS |
| Interventions | AAI versus dual chamber pacing |
| Outcomes | Total mortality |
| Starting date | 350 patients randomised February 2001 (active recruitment ongoing) |
| Contact information | HR Anderson, Department of Cardiology, Skejby Sygehus, Arhus, Denmark |
| Notes | Recruitment expected to last 6 years; follow‐up of 5.5 years planned |
STOP‐AF.
| Study name | Systematic trial of pacing to prevent atrial fibrillation |
| Methods | |
| Participants | 235 patients with SSS (mean age 73) |
| Interventions | AAI(R) or DDD(R) versus VVI(R) |
| Outcomes | Atrial fibrillation, pacemaker syndrome, worsening congestive heart failure |
| Starting date | Trial ongoing in 2001; no data identified at time of completion of the report |
| Contact information | RG Charles, Cardiothoracic Centre, Liverpool NHS Trust, Thomas Drive, Liverpool, UK |
| Notes |
UKPACE.
| Study name | The UK pacing and cardiovascular events trial |
| Methods | |
| Participants | 2000 patients >/= 70 years with AV block |
| Interventions | DDD versus VVI or VVIR |
| Outcomes | All cause mortality, quality of life, exercise capacity, cardiovascular events, cost‐utility |
| Starting date | Study completed; data expected to become available 2003 |
| Contact information | WD Toff, Department of Cardiology, Glenfield Hospital, Leicester, UK |
| Notes |
Contributions of authors
Janine Dretzke was the main author. She designed the protocol; undertook the searches; assessed studies for eligibility; extracted all data; performed the quality assessment; liaised with experts and wrote and collated the review.
Rod Taylor was the project manager and takes overall responsibility for the report. He advised on protocol development; undertook quality assessment of a subset of studies; provided statistical advice; liaised with experts and assisted in the writing of the review.
William Toff provided clinical guidance; advised on the protocol and assisted in the writing of the review.
Gregory YH Lip assisted in the protocol development; provided clinical guidance and commented on the draft review.
James Raftery advised on the protocol and assisted in the writing of the review.
Anne Fry‐Smith advised on the search strategies and assessed a subset of studies for eligibility.
Sources of support
Internal sources
Dept of Public Health and Epidemiology, University of Birmingham, UK
City Hospital, Brimingham, UK
Glenfield Hospital, Leicester, UK
Health Services Management Centre, University of Birmingham, UK
External sources
Regional NHS Executive, UK
Declarations of interest
J Dretzke ‐ None WD Toff ‐ Joint principal investigator for the UKPACE trial; received fees for speaking, support for research and expenses for attending meetings from pacemaker manufacturers and suppliers including ELA Medical, Guidant, St Jude Medical and Medtronic GYH Lip ‐ None J Raftery ‐ None A Fry‐Smith ‐ None R Taylor ‐ Consultancy work for Medtronic (Europe) in a therapeutic area not closely associated with pacemakers.
Stable (no update expected for reasons given in 'What's new')
References
References to studies included in this review
Avery {published data only}
- Avery B, Banning A, Lawson T, McGurk L, Buchalter M. Physiological pacing improves symptoms and increases exercise capacity in the elderly patient. International Journal of Cardiology 1994;46(2):129-33. [DOI] [PubMed] [Google Scholar]
Boon {published data only}
- Boon NA, Frew AJ, Cobbe SM. An intra-patient comparison of ambulatory blood-pressure during chronic DDD and VVI pacing. British Heart Journal 1986;55(5):508. [DOI] [PMC free article] [PubMed] [Google Scholar]
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CTOPP {published data only}
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Deharo {published data only}
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Hargreaves {published data only}
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Lau (1) {published data only}
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Lau (2) {published data only}
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