Abstract
Aims
Correctly identifying patients who will benefit from cardiac resynchronization therapy (CRT) is still challenging. ‘Apical rocking’ is observed in asynchronously contracting ventricles and is associated with echocardiographic response to CRT. The association of apical rocking and long-term clinical outcome is however unknown at present. We assessed the predictive value of left ventricular (LV) apical rocking on a long-term clinical outcome in patients treated with CRT.
Methods and results
Consecutive heart failure patients treated with primary indication for CRT-D between 2005 and 2009 were included in a prospective registry. Echocardiography was performed prior to CRT to assess apical rocking, defined as motion of the LV apical myocardium perpendicular to the LV long axis. Major adverse cardiac event (MACE) was defined as combined end point of cardiac death and/or heart failure hospitalization and/or appropriate therapy (ATP and/or ICD shocks). All echocardiograms were assessed by independent cardiologists, blinded for clinical data. Multivariable analyses were performed to adjust for potential confounders. Two hundred and ninety-five patients with echocardiography prior to implantation were included in the final analyses. Apical rocking was present in 45% of the study patients. Apical rocking was significantly more common in younger patients, females, patients with sinus rhythm, non-ischaemic cardiomyopathy, and in patients with LBBB and wider QRS duration. During a mean clinical follow-up of 5.2 ± 1.6 years, 92 (31%) patients reached the end point of the study (MACE). Patients with MACE had shorter QRS duration, had more ischaemic cardiomyopathy, and were more often on Amiodarone. In univariate analyses, MACE was associated with shorter QRS duration, ischaemic aetiology, and the absence of apical rocking. After multivariable analyses, apical rocking was associated with less MACE (hazards ratio, HR 0.44, 95% confidence interval, CI 0.25–0.77).
Conclusion
Apical rocking is an independent predictor of a favourable long-term outcome in CRT-D patients.
Keywords: apical rocking, long-term outcome, cardiac resynchronization therapy, ICD therapy
Introduction
Several clinical trials have demonstrated that cardiac resynchronization therapy (CRT) reduces heart failure symptoms, hospitalization, and mortality. CRT improves cardiac function in the majority of patients with symptomatic heart failure and reduced left ventricular ejection fraction (LVEF ≤35%) with wide QRS (>120–130 ms).1–4 However, present guidelines for selection of CRT candidates result in 30–40% non-responders and even worsening of cardiac function in some patients.5,6 The challenges of correctly identifying patients who will benefit from this costly therapy therefore remain. One of the factors that may influence the likelihood of response to CRT is the lack or presence of left ventricular dyssynchrony. The definition and evaluation of LV-dyssynchrony are still subject to debate. Different echocardiographic parameters have been proposed to identify potential CRT responders, without consensus on the predictive value of any of these parameters.7–12 In the past years, left ventricular apical rocking has been introduced as a new parameter for the assessment of left ventricular dyssynchrony.13,14 A short initial septal contraction within the isovolumic contraction period results in a short inward motion of the septum and causes the apex to move septally. The delayed activation of the lateral wall then pulls the apex laterally during the ejection time while stretching the septum. This typical motion pattern of the apex of left ventricle is described as ‘apical rocking’. Only few studies have assessed the value of apical rocking in predicting CRT response.13–15 Moreover, these studies were small sized and described only echocardiographic CRT response. The aim of our current study was to assess the independent predictive value of apical rocking on long-term clinical outcomes in a large study population.
Methods
Selection of patients
From January 2005 to December 2009, 347 consecutive patients with primary indication for CRT-D implantation were included in a prospective registry and followed for a median of 5.2 years [inter-quartile range (IQR) 4.5–6.5]. This registry was approved by the institutional review board. Patients were excluded from the analyses if (1) patients received CRT without defibrillation therapy (CRT-P), (2) pre-implantation LVEF was ≥35% according to echocardiographic data, and (3) patients had a recent myocardial infarction or CABG (<3 months). To be included in the final analysis, the patients were required to have an echocardiogram before CRT-D implantation and during follow-up. Based on these criteria, a total of 295 patients were included in the analyses (Figure 1). Indication for CRT-D implantation was determined according to the guidelines at the time of implantation. In all patients, LVEF was ≤35% and QRS duration was >120 ms because of LBBB, RBBB, or non-specific intra-ventricular conduction disorders (IVCD). Heart failure was diagnosed according to the European Society of Cardiology guidelines, and the severity of symptoms was categorized into four functional classes as defined by the New York Heart association (NYHA) criteria. Aetiology was considered ischaemic in the presence of significant coronary artery disease (≥50% stenosis in one or more of the major epicardial coronary arteries) corresponding with the area of wall motion abnormality and/or history of myocardial infarction or prior revascularization by PCI or CABG. Medical therapy was optimized to reach the highest tolerated dosages of angiotensin-converting enzyme inhibitors and β-blockers.
Figure 1.
Flowchart of study population.
Device implantation
CRT devices from all major manufacturers (Medtronic Inc., St Jude Medical, Boston-scientific, Biotronik, and Sorin Group) were implanted. The majority of coronary sinus leads were bipolar and were positioned in the lateral, posterolateral, or posterior region when feasible (83%). The anterior and anterolateral positions were considered suboptimal and avoided if possible (8%). Nine percentage of left ventricular leads were positioned epicardially during open heart surgery prior to CRT-D implantation. After implantation, tailored device programming was performed before discharge with three consecutive zones in the large majority of patients. A monitor zone between 170 and 200 bpm, anti-tachycardia pacing (ATP), and shock therapy zone between 200 and 230 bpm and a shock zone >230 bpm. In the ATP and shock therapy zone, arrhythmias were initially attempted to be terminated by two bursts and one ramp, and defibrillator shocks were used if the arrhythmia continued. Routine follow-up visits were scheduled at 2 months post-implant, and every 6 months thereafter. As part of usual care, during follow-up, ICD printouts were obtained to determine the number and type of arrhythmias and number of appropriate and inappropriate shocks. The routine follow-up in some of our patients took place in referring hospitals.
Data collection
Baseline characteristics included age, gender, aetiology of heart failure, clinical history, medical therapy, and NYHA functional class. ECG and procedural data were collected prospectively and analysed retrospectively. The clinical status of all patients was verified at the closure of the study (December 2013).
Echocardiographic data acquisition
All patients underwent two-dimensional echocardiography before biventricular ICD implantation and at follow-up in the second year after CRT implantation. The images were obtained on a Vivid 7 ultrasound machine (General Electric, Milwaukee, WI, USA) using a 3.5 MHz transducer at a depth of 16 cm in the parasternal (long and short axis) and apical (two and four chambers) views. The images were stored in cine-loop format by well-trained echocardiographists and reviewed by an independent cardiologist who was not involved in the study. The left ventricular end-diastolic diameter (LVEDD), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic diameter (LVESD), and left ventricular end-systolic volume (LVESV) were measured and the LVEF was calculated using Simpson's technique.16
Visual assessment of LV-apical rocking
Apical rocking was defined as a short initial septal contraction that results in short inward motion of the septum and pulls the apex to the septum and then the delayed activation of the lateral wall that pulls the apex laterally during the ejection time while stretching of the septum takes place. This definition was used to assess visually the presence of apical rocking. The presence of apical rocking was visually assessed in four-chamber apical view by three cardiologists each with >6 years of echocardiography experience. All cardiologists had only access to the grey-scale image loops of the three apical image planes and were unaware of any patient data including information about the response to CRT. Inter-observer and intra-observer agreement were expressed as kappa coefficients. Values >0.8 are considered as excellent, values between 0.6 and 0.8 as good, values between 0.4 and 0.6 as moderate, and values below 0.4 as poor agreement.
Event sub-classification and definitions
Data on mortality were collected from reviewing our hospital records, referring hospitals, and by contacting general practitioners. Causes of death were categorized into two groups, cardiac death and non-cardiac death according to the previous study.17 The cardiac death was further categorized into death from ventricular tachyarrhythmia, heart failure-related death, and sudden cardiac death. Non-cardiac death was further divided into malignancy, infection including sepsis and pneumonia, chronic obstructive pulmonary disease, and aortic dissection. In two patients, the cause of death was classified as unknown (in one patient, the family physician was unknown, and in another, patient digital file was not present).
End point
Major adverse cardiac event (MACE) was defined as the combined end point of cardiac death and/or heart failure hospitalization and/or appropriate therapy (ATP and/or ICD shocks).
Statistical analysis
Statistical analysis was performed using SPSS Statistics for Windows, Version 22.0 (IBM Corp., Armonk, NY, USA). Continuous variables are expressed as mean ± SD, and significance of differences between independent groups was calculated using the non-parametric Mann–Whitney U test. Categorical variables are presented as number and percentages, and significance of differences between groups was calculated using the χ2 test or Fisher's exact test as appropriate. Cox regression analysis was performed to assess the association of apical rocking with MACE. Clinical variables (age, gender, LVEF, sinus rhythm or atrial fibrillation, QRS width, LBBB/RBBB, and ischaemic/non-ischaemic cardiomyopathy) were entered into the Cox regression analysis as confounders. Time until MACE was plotted using Kaplan–Meier estimates, and groups were compared using log-rank tests. We evaluated the additional value of apical rocking above clinical variables (age, gender, LVEF, sinus rhythm or atrial fibrillation, QRS width, LBBB/RBBB, and ischaemic/non-ischaemic cardiomyopathy) in prediction of MACE by means of the likelihood ratio test. The likelihood ratio test is the difference between the −2 log likelihood of the model with and the model without apical rocking, which is χ2 distributed with 1 df. P-values <0.05 were considered statistically significant in all analyses.
Results
Initially, 347 patients with prophylactic CRT-D indication were registered in our hospital database. In 50 patients, echocardiographic evaluation before the implantation was not available; in 2 patients, the assessment of apical rocking was not possible due to poor image quality. Therefore, the study population consisted of 295 patients. Mean age was 67 ± 9 years with 30% female gender. Mean NYHA functional class was 2.5 ± 0.6, and 81% had LBBB with mean QRS duration of 155 ± 30 ms. Mean LVEF was 24.8 ± 6.6%; non-ischaemic aetiology was present in 49% of patients. Apical rocking was present in 45% of patients. Apical rocking was significantly more common in younger patients, females, patients with sinus rhythm, non-ischaemic cardiomyopathy, in patients with LBBB, and wider QRS duration. All patients were on optimal medical therapy for heart failure. General characteristics of total study population and according to the presence or absence of apical rocking are summarized in Table 1.
Table 1.
General characteristics of study population according to apical rocking
| All patients (n = 295) | Patients with apical rocking (n = 133) | Patients without apical rocking (n = 162) | P-value | |
|---|---|---|---|---|
| Age (years) | 67 ± 9 | 65 ± 10 | 69 ± 8 | 0.001 |
| Female | 30% | 41% | 22% | <0.001 |
| LVEF (%) | 24.8 ± 6.6 | 25.0 ± 6.8 | 24.7 ± 6.5 | 0.929 |
| Sinus rhythm | 75% | 81% | 71% | 0.038 |
| QRS duration (ms) | 155 ± 30 | 164 ± 29 | 148 ± 29 | <0.001 |
| LBBB | 81% | 91% | 73% | <0.001 |
| RBBB | 6% | 3% | 9% | 0.055 |
| IVCD | 12% | 6% | 18% | 0.003 |
| NYHA functional class | 2.5 ± 0.6 | 2.5 ± 0.7 | 2.5 ± 0.6 | 0.637 |
| Non-ischaemic aetiology | 49% | 71% | 31% | <0.001 |
| Diuretics | 82% | 77% | 86% | 0.044 |
| β-Blocker | 82% | 85% | 80% | 0.290 |
| AT-II receptor blockers | 43% | 48% | 40% | 0.137 |
| ACE-inhibitors | 76% | 77% | 75% | 0.782 |
| Spironolacton | 44% | 42% | 45% | 0.611 |
LVEF, left ventricular ejection fraction; LBBB, left bundle branch block; RBBB, right bundle branch block; IVCD, intra-ventricular conduction disorder; NYHA, New York heart association.
Inter- and intra-observer variability
To quantify the inter- and intra-observer variability for assessment of apical rocking, we reviewed 140 (47%) patients by three cardiologists. The inter-observer variability kappa was 0.85, and intra-observer variability kappa was 0.90.
Long-term outcome
Patients were followed for 5.2 ± 1.6 years and 85.5% completed at least 4 years of follow-up. During follow-up, 63 (21%) patients died. In 97% patients, the mode of death was obtained, 52% (33 patients) had a cardiac death. During follow-up, 21% (62/295) of patients were admitted to the hospital due to worsening of heart failure. Appropriate CRT-D (ATP or ICD-shock) intervention occurred in 12% (36/295) of patients and inappropriate CRT-D intervention in 10% (31/295) of patients. Total MACE occurred in 31% of the patients (Table 2). During follow-up, the patients with apical rocking had significantly better NYHA functional class, had higher LVEF, and experienced higher percentage of biventricular pacing compared with patients without apical rocking. All-cause mortality was significantly lower in patients with apical rocking compared with patients without apical rocking (13 vs. 28% P < 0.001). Furthermore, MACE was significantly lower in patients compared with patients without apical rocking (19 vs. 41%, P < 0.001; Table 2).
Table 2.
Clinical end points of the study population according to apical rocking during long-term follow-up
| All patients (n = 295) | Patients with apical rocking (n = 133) | Patients without apical rocking (n = 162) | P-value | |
|---|---|---|---|---|
| Clinical follow-up duration (years) | 5.2 ± 1.6 | 5.5 ± 1.5 | 5.0 ± 1.6 | 0.016 |
| NYHA functional class follow-up (mean ± SD) | 2.0 ± 0.8 | 1.8 ± 0.8 | 2.1 ± 0.7 | 0.003 |
| LVEF follow-up (%) (mean ± SD) | 36.6 ± 12.2 | 42.8 ± 10.5 | 31.6 ± 11.2 | <0.001 |
| Percentage biventricular pacing | 93.8 ± 13.4 | 95.3 ± 9.0 | 92.6 ± 16.2 | 0.061 |
| Appropriate ATP therapy | 6% | 4% | 7% | 0.181 |
| Appropriate ICD shock | 9% | 5% | 12% | 0.036 |
| Inappropriate ICD shock | 10% | 9% | 12% | 0.451 |
| All-cause mortality | 21% | 13% | 28% | 0.001 |
| Non-cardiac and unknown cause of death | 10% | 8% | 12% | 0.328 |
| MACE | 31% | 19% | 41% | <0.001 |
| Appropriate therapy (ATP and/or shock) | 12% | 9% | 15% | 0.130 |
| Heart failure hospitalization | 21% | 11% | 29% | <0.001 |
| Cardiac death | 11% | 5% | 17% | 0.001 |
ATP, anti-tachy pacing; ICD, implantable cardioverter defibrillator; MACE, major cardiac adverse event.
Apical rocking and MACE
A total of 204 patients (69%) survived without heart failure hospitalization or appropriate therapy (ATP and/or ICD shocks). A total of 91 (31%) patients died from cardiac death or were hospitalized with heart failure or treated appropriately with ICD, and were classified as patients with MACE. Patients with MACE had significantly shorter QRS duration, had more ischaemic aetiology, and were more on amiodarone. Furthermore, NYHA functional class was higher and the percentage of biventricular pacing was lower compared with patients without MACE (Table 3). The presence of apical rocking between the patients with and without MACE was significantly different (27 vs. 53%, respectively, P < 0.001) (Table 3 and Figure 2). Results of both univariate and multivariate analyses of the association between apical rocking and MACE are summarized in Table 4. In univariate analyses, MACE was associated with shorter QRS duration, ischaemic aetiology, and the absence of apical rocking. In multivariate analyses, the incidence of MACE was lower in patients with apical rocking (hazards ratio, HR 0.44, 95% confidence interval, CI 0.25–0.77, P = 0.004) and those with shorter QRS duration (HR 0.87, 95% CI 0.79–0.96, P = 0.005). The value of the likelihood ratio test of the comparison of the model with and the model without apical rocking is 8.90 (df = 1) with significant P-value (P = 0.003).
Table 3.
General characteristics of study population according to MACE
| All-patients (n = 295) | Patients without MACE (n = 204) | Patients with MACE (n = 91) | P-value | |
|---|---|---|---|---|
| Age (years) | 67 ± 9 | 67 ± 9 | 68 ± 9 | 0.176 |
| Female | 30% | 32% | 27% | 0.432 |
| LVEF (%) baseline | 24.8 ± 6.6 | 25.0 ± 6.9 | 24.3 ± 6.0 | 0.513 |
| LVEF (%) follow-up | 36.6 ± 12.2 | 39.5 ± 11.2 | 30.2 ± 11.8 | <0.001 |
| Sinus rhythm | 75% | 79% | 68% | 0.064 |
| QRS duration (ms) | 155 ± 30 | 159 ± 31 | 147 ± 27 | 0.001 |
| LBBB | 81% | 81% | 82% | 0.904 |
| RBBB | 6% | 7% | 5% | 0.590 |
| IVCD | 12% | 12% | 13% | 0.794 |
| NYHA functional class | 2.5 ± 0.6 | 2.5 ± 0.6 | 2.6 ± 0.6 | 0.248 |
| Non-ischaemic aetiology | 49% | 54% | 38% | 0.013 |
| Diuretics | 82% | 80% | 86% | 0.225 |
| β-Blocker | 82% | 83% | 80% | 0.604 |
| AT-II receptor blockers | 43% | 43% | 43% | 0.929 |
| ACE-inhibitors | 76% | 75% | 77% | 0.703 |
| Spironolacton | 44% | 42% | 47% | 0.490 |
| LV-lead position | ||||
| Posterior/posterolateral | 204 (69%) | 138 (67%) | 66 (72%) | NS |
| Lateral | 47 (16%) | 34 (17%) | 13 (14%) | NS |
| Anterolateral/anterior | 13(4%) | 10 (5%) | 3 (3%) | NS |
| Mid cardiac vein | 8 (3%) | 6 (3%) | 2 (2%) | NS |
| Epicardial | 23 (8%) | 16 (8%) | 7 (7%) | NS |
| Apical position | 89 (33%) | 55 (29%) | 34 (40%) | NS |
| Non-apical position | 183 (67%) | 133 (71%) | 50 (59%) | NS |
| Clinical follow-up duration (years) | 5.2 ± 1.6 | 5.5 ± 1.4 | 4.6 ± 1.7 | <0.001 |
| NYHA class follow-up (mean ± SD) | 2.0 ± 0.8 | 1.9 ± 0.8 | 2.3 ± 0.7 | 0.001 |
| Percentage biventricular pacing | 93.8 ± 13.4 | 95.5 ± 9.8 | 90.1 ± 18.8 | 0.005 |
| Presence of apical rocking | 45% | 53% | 27% | <0.001 |
All abbreviations are explained in Table 1.
Figure 2.
MACE-free survival in patients with and without apical rocking.
Table 4.
Uni- and multivariable predictors of MACE
| Univariable |
Multivariable |
|||||
|---|---|---|---|---|---|---|
| HR | 95% CI | P-value | HR | 95% CI | P-value | |
| Age (years) | 1.02 | 1.00–1.05 | 0.086 | 1.02 | 0.99–1.05 | 0.197 |
| Female | 0.79 | 0.50–1.25 | 0.317 | 1.43 | 0.85–2.39 | 0.176 |
| LVEF (%) baseline | 0.99 | 0.96–1.02 | 0.580 | 0.98 | 0.95–1.02 | 0.364 |
| Sinus rhythm vs. Afib | 0.59 | 0.37–0.93 | 0.024 | 0.65 | 0.37–1.14 | 0.136 |
| QRS duration (per 10 ms) | 0.91 | 0.85–0.97 | 0.005 | 0.87 | 0.79–0.96 | 0.005 |
| LBBB vs. non-LBBB | 0.94 | 0.53–1.68 | 0.843 | 0.59 | 0.31–1.12 | 0.108 |
| Non-ischaemic aetiology | 0.58 | 0.38–0.88 | 0.010 | 0.63 | 0.37–1.07 | 0.084 |
| Presence of apical rocking | 0.39 | 0.25–0.62 | <0.001 | 0.44 | 0.25–0.77 | 0.004 |
All abbreviations are explained in Table 1.
Apical rocking in patients with QRS <150 ms
Sub-analysis of patients with QRS <150 ms identified 108 patients. Apical rocking was present in 30% (33) of patients compared with 53% in patients with QRS ≥150 ms (P < 0.001). MACE was more common in patients without apical rocking compared with patients with apical rocking (49 vs. 24%, P = 0.015).
Apical rocking in patients with ischaemic aetiology
Wall motion abnormalities (scar tissue due to myocardial infarction) were assessed in all 150 (51%) patients with ischaemic aetiology. Forty-three percentage of patients had wall motion abnormalities in the anterior or antero-septum segments. Among this group, only 3% had apical rocking compared with 35% apical rocking in patients without wall motion abnormality in anterior or antero-septum segments.
Discussion
In the present study, we assessed the association of baseline apical rocking with MACEs during long-term follow-up in patients who underwent CRT-D implantation. This study showed that the presence of apical rocking before CRT is independently associated with a lower incidence of long-term MACE. The significant P-value of the likelihood ratio test supports the additional value of apical rocking above clinical variables in prediction of long-term MACE.
Apical rocking
In the past years, several dyssynchrony indices have been developed to identify patients who will respond to CRT with promising results in single centre trials. Unfortunately, these indices have performed poorly in larger clinical trials, showing high inter-observer variability and failing to accurately segregate responders and non-responders to CRT before the implantation.6,9,10,12,18–21
Apical rocking is a typical early septal contraction in patients with left bundle branch block, which pulls the apex towards the septum. Delayed activation of the lateral wall pulls then the apex laterally during the ejection time while the septum is stretching. Apical rocking can be visualized in a standard echocardiographic four-chamber view in patients with left ventricular dyssynchrony. This is in contrast to several dyssynchrony indices, which require well-trained echocardiographist and special imaging software and techniques. Both regional myocardial functional abnormalities (due to scar tissue) and temporal abnormalities (due to activation delay) contribute to apical rocking, and thus, both are incorporated in a single echocardiographic parameter.22,23 In current study, among the group of patients with scar tissue in distal part of septum or antero-septum due to myocardial infarction, only 3% had apical rocking compared with 35% in patients with scar tissue in other part of LV. It suggests that scar tissue in distal part of septum or antero-septum affects the presence of apical rocking. Apical rocking retains important regional information on the myocardial contraction sequence24 and overcomes several limitations of peak velocity parameters and avoids the challenges of myocardial deformation measurements. The ability of apical rocking to reflect LV mechanical dyssynchrony has already been demonstrated by its superior predictive power for echocardiographic CRT response.13 Previous studies compared a quantitative measurement of apical rocking, defined as the percentage of the cardiac cycle with reverse motion of the septum and the apex, with visual assessment of apical rocking and demonstrated a comparable accuracy in predicting CRT response.13,25 We recently published our data on the predictive value of apical rocking in 137 patients and showed the association of apical rocking with both long-term echocardiographic response and incidence of heart failure.15
In the current study, we had a much larger number of CRT patients, which consisted of CRT-D patients (CRT and defibrillator therapy). We used MACE during long-term follow-up as outcome measure. CRT results in positive remodelling of the ventricles and had beneficial effects on cardiac function. This is reflected in both reduction in heart failure symptoms and hospitalization, and also a reduction of cardiac mortality and ventricular tachyarrhythmias (e.g. appropriate ICD therapy). Therefore, MACE is one of the most robust clinical outcome measures reflecting CRT success. The current study, for the best of our knowledge, is the first and largest study which assessed the association between apical rocking and long-term MACE. The predictive value of the absence of apical rocking has been recently studied in a relatively small cohort of CRT patients (n = 40) in which the absence of apical rocking predicted early haemodynamic non-response after 1 month of CRT.14 One of the major issues in assessment of LV-dyssynchrony is the applicability of a dyssynchrony index in daily clinical practice. One of the advantages of visual assessment of apical rocking, contrary to several other dyssynchrony indices, is that it can be assessed relatively easy and is not time consuming. Other indices have lower inter- and intra-observer agreements, even in core echocardiographic centres.6 It seems that there is a relationship between QRS duration and the presence of apical rocking. In total study population, apical rocking was present in 45% of patient while in patients with QRS <150 ms is 30%. One of the disadvantages of apical rocking is that not every patient with classic CRT indication shows apical rocking. In our study population, apical rocking was present in only 45% of patients, whereas 70% of the study population did not have MACE. However, when apical rocking is present, the percentage of MACE during long-term follow-up is only 19% compared with 41% when apical rocking was not present. Apical rocking was present in 53% of patients without MACE and in 27% of patient with MACE.
Clinical implication of apical rocking
Visual assessment of apical rocking is relatively easy and is reproducible. Although current patient selection guidelines for CRT utilize QRS width as a surrogate for dyssynchrony, the results of our study support the additional value of apical rocking in prediction of long-term MACE. Further prospective and multicentre studies are needed to confirm our findings, particularly in patients with QRS duration <150 ms.
Strengths and limitations
Both the large number of the study population and the long-term clinical follow-up are probably the major strengths of the current study. There are also several limitations of this study. It concerns a prospective registry of consecutive patients treated with CRT-D in a high experienced CRT centre. A subgroup analysis is limited by limited numbers in each group. Visual assessment of apical rocking may be inferior to measuring of the motion and velocities of myocardial walls in mm and cm/s. Since the start of the study, several new echocardiographic dyssynchrony indices have been introduced, particularly with the calculation of apical transverse motion.14,22 However, the study by Tournoux et al.14 compared a quantitative measurement of apical rocking, defined as the percentage of the cardiac cycle with reverse motion of the septum and the apex, with visual assessment of apical rocking and demonstrated a comparable accuracy in predicting CRT response. The current study population resembles most closely daily practice with inclusion of patients with atrial fibrillation and we demonstrated that visualization of apical rocking was not negatively influenced by the inclusion of patients with atrial fibrillation. A new ischaemic event in patients with ischaemic aetiology during long-term follow-up can affect the outcome of the patients. Unfortunately, data on new ischaemic event in our study population are not available, which is an important limitation. Suboptimal LV-lead placement must also be considered. However, care was taken to minimize this risk by coronary venogram-guided lead placement and all leads were placed in the posterior or lateral region if possible. Unfortunately, we were not able to perform echo-guided optimization after device implantation. In the present study, the echocardiograms and assessment of apical rocking were performed at rest. Recent publication suggested,26 however, that low-dose dobutamine stress echocardiography could result in more dyssynchrony and might improve the predictive value of apical rocking.
Conclusion
We demonstrated that apical rocking was present in 45% of the study population. Apical rocking before CRT is independently associated with a lower incidence of long-term MACE.
Conflict of interest: none declared.
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