Abstract
Background:
Prolonged monitoring of cardiac rhythm has been used to screen for subclinical atrial fibrillation (AF); little is known about other arrhythmias in the general population, especially in the elderly, who are at higher risk of arrhythmias.
Methods:
We evaluated the frequency of arrhythmias in the tri-ethnic (white, Black, Hispanic), community-based Subclinical Atrial Fibrillation and Risk of Ischemic Stroke (SAFARIS) study using a patch-based recorder for up to 14 days in 527 participants free of AF, congestive heart failure (CHF) or history of stroke. Differences according to gender, age, ethnicity and presence of hypertension, diabetes and pertinent ECG and echocardiographic variables were examined.
Results:
Mean age was 77.2±6.8 years (37.2% men, 62.8% women). AF was present in 10 participants (1.9%), only 2 of them symptomatic. Supraventricular tachycardia (SVT) and ventricular tachycardia (VT) episodes were observed in 84.4% and 25.0% but only 13.5% and 10.6% of participants reported symptoms, respectively. Severe bradycardia (<40 bpm) was present in 12.5%. Sinus pauses and high-degree atrioventricular blocks were infrequent (2.1% and 1.5%, respectively). Most arrhythmias were more frequent in participants >75 years; ventricular arrhythmias and severe bradycardia were more common in men. Whites had significantly more episodes of AF than Hispanics, SVT than Blacks and VT≥10 beats than Hispanics and Blacks. Hypertensives had more episodes of severe bradycardia. LV hypertrophy or LVEF <55% were associated with more frequent ventricular and supraventricular arrhythmias.
Conclusions:
Prolonged cardiac rhythm monitoring revealed moderate frequency of AF, but higher than expected frequencies of AF-predisposing arrhythmias. Ventricular arrhythmias were relatively frequent, whereas severe bradyarrhythmias were infrequent.
Keywords: cardiac arrhythmias; electrocardiography; atrial fibrillation; tachycardia; bradycardia; cardiac complexes, premature
1. Introduction
Prolonged cardiac monitoring is changing the approach to the study of rhythm abnormalities in the population. Ambulatory electrocardiographic (ECG) monitoring and implantable devices have shown to be superior to the standard-of-care Holter monitoring in individuals with definite clinical indications for cardiac rhythm monitoring (1, 2). Recently, ECG-recording patch-based devices have proven their efficacy and feasibility for conducting prolonged noninvasive ambulatory monitoring in the general population (3, 4). For screening purposes, the length of the recording makes a difference; monitoring using a cardiac patch for up to 4 weeks identified 78% more episodes of subclinical atrial fibrillation (AF) than 2 weeks (5). However, most of the data available to date are mainly limited to screening for subclinical AF, while the prevalence of other cardiac arrhythmias in the general population is not clearly established (6). In the past, several studies have looked at the presence of rhythm abnormalities in the population using clinical records (7, 8); limited information is therefore available in the general population without overt cardiovascular disease. This aspect is of particular relevance in the elderly, who have high frequency of cardiovascular risk factors predisposing to arrhythmias, and are more likely to remain asymptomatic during arrhythmic episodes (9).
The Subclinical Atrial Fibrillation and Risk of Ischemic Stroke (SAFARIS) study set out to investigate the frequency of undetected AF and its possible predictors in a community-based sample of the older population residing in Northern Manhattan, using continuous recording of the cardiac rhythm for up to 14 days with a patch-based recording device. The frequency of other arrhythmias, such as supraventricular tachycardia (SVT), ventricular tachycardia (VT), premature atrial (PACs) and ventricular (PVCs) contractions, and bradyarrythmias was also analyzed. In addition, we examined the possibility of differences among the frequency of arrhythmias according to gender, age <75 or ≥75 years, ethnicity, presence of hypertension or diabetes or pertinent ECG and echocardiographic abnormalities.
2. Methods
Participants in SAFARIS underwent continuous cardiac rhythm monitoring and echocardiographic assessment. SAFARIS participants were drawn from the Cardiovascular Abnormalities and Brain Lesion (CABL) study and the parent Northern Manhattan Study (NOMAS), a population-based prospective study to investigate the epidemiology and risk factors for stroke and cardiovascular disease that enrolled participants from the community living in northern Manhattan between 1993 and 2001. The study design and recruitment details of NOMAS and CABL have been described previously (10). From August 2014 to December 2019, CABL and NOMAS participants who agreed to undergo a new extensive cardiovascular evaluation, including 14-day monitoring of cardiac rhythm, were included in SAFARIS and constitute the cohort of the present report. Exclusion criteria were history of AF, stroke or congestive heart failure (CHF) as ascertained by questionnaire and available history of hospital admissions. Written informed consent was obtained from all study participants. The study complies with the Declaration of Helsinki and was approved by the Institutional Review Boards of Columbia University Medical Center and the University of Miami.
2.1. Electrocardiographic information
The Zio Patch XT (iRhythm Technologies Inc., San Francisco, CA) used for cardiac monitoring is an adhesive cardiac monitoring patch that provides an effective method for prolonged ECG monitoring, as demonstrated previously (5). The recorder was applied by trained research assistants, who also retrieved it at the end of monitoring and shipped it to the manufacturer for analysis. Analyzable time was defined as the total time during which the monitor provided a tracing adequate to determine cardiac rhythm. AF was defined as an irregularly irregular rhythm with absent P waves lasting at least 30 seconds.
Arrhythmias adjudication by iRhythm was based on a 2-step process. First, the ECG data were interrogated using a Food and Drug Administration–cleared, proprietary algorithm to identify the heart rate and irregularity episodes. Next, trained and certified cardiovascular technicians reexamined the detected abnormal rhythm episodes to confirm the diagnoses. The standard report included a diagnosis summary and ECGs. Data on wear time and analyzable time were also obtained from the standard report. Finally, a team of physician ECG readers verified the accuracy of the findings. The report was then reviewed and edited as necessary by SAFARIS physicians.
SVT and VT were defined as ≥4 PACs or ≥4 PVCs in a row, respectively. Bradycardia was considered as heart rate <60 bpm. The presence and frequency of PACs and PVCs, first degree and high-grade atrio-ventricular blocks (AVB) (2nd degree Mobitz II and 3rd degree block) and sinus pauses of ≥3 seconds were also reported. Additional ECG abnormalities considered were the frequency of PR interval ≥200 ms, QRS duration ≥120 ms and QTc interval ≥440 ms, which were present in 89 (16.9%), 51 (9.7%) and 130 (24.7%) participants, respectively.
2.2. Echocardiographic assessment
Transthoracic echocardiography was performed using a commercially available system (Sonos 5500 or 7500; iE33; Philips, Andover, Massachusetts) by a trained registered sonographer following a standardized protocol. The LV and LA linear dimensions were measured from a parasternal long-axis view according to the recommendations of the American Society of Echocardiography. LA antero-posterior diameter was measured; the cutoff value of ≥40 mm was considered as abnormal and was present in 224 (42.5%) participants. LV mass was calculated with a validated method (11) and indexed by BSA (LV mass index). Left ventricular ejection fraction (LVEF) was determined using modified biplane Simpson’s rule, and LVEF ≤55% was considered as abnormal and was present in 37 (7%) of subjects. Left ventricular hypertrophy (LVH) was defined as shown previously (12) and was present in 126 (23.9%) participants.
2.3. Risk factors assessment
Cardiovascular risk factors were determined through direct examination and interview by trained research assistants. Hypertension was defined as systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90 mmHg at the time of the visit (mean of two readings), or patient’s self-reported history of hypertension or use of antihypertensive medications. Diabetes was defined as fasting blood glucose ≥126 mg/dL or patient’s self-reported history of diabetes or use of diabetes medications.
2.4. Statistical analysis
Data are presented as mean ± standard deviation for continuous variables, and as frequencies and percentages for categorical variables.
Frequency of arrhythmias was assessed according to distribution in general population, sex, age (<75 and ≥75), ethnicities (white, Black, Hispanics), presence of hypertension and diabetes. Additional analyses were conducted for electrocardiographic (PR≥200 ms, QRS≥ 120ms, QTc ≥440 ms) and echocardiographic (LA size ≥40 mm, LVH, LVEF≤55%) abnormalities possibly associated with arrhythmias.
Differences in frequency of arrhythmias by categories of interest were examined with chi square tests. Analyses were conducted using SAS version 9.4 (SAS Institute, Cary, NC), and P values less than 0.05 were considered statistically significant.
3. Results
3.1. Characteristics of the study population
Diagnostically adequate monitoring of cardiac rhythm was available in all 527 subjects (196 men, 331 women) who completed at least 2 days of recording; 5 participants (0.9%) refused or were unable to tolerate the monitoring; 8 participants (1.5%) wore the patch for less than 48h and were excluded from the analysis. Recording duration was over 10 days in 91% of participants, and over 13 days in 84%. Clinical and demographic characteristics of the study cohort are shown in Table 1. Mean age of the study group was 77.2±6.8 years.
Table 1.
Demographic and clinical characteristics of the study population
| N=527 | |
|---|---|
| Age, y | 77.2±6.8 |
| Men, n (%) | 196 (37.2) |
| BMI, kg/m2 | 28.5±5.2 |
| HR, beats/min | 73.8±8.8 |
| Systolic BP, mm Hg | 129.0±14.8 |
| Diastolic BP, mm Hg | 74.5±8.8 |
| Hypertension, n (%) | 443 (84.1) |
| Diabetes, n (%) | 196 (37.2) |
| Hypercholesterolemia, n (%) | 414 (78.6) |
| CAD, n (%) | 29 (5.5) |
| Cigarette smoking, n (%) | 260 (49.3) |
| Race-ethnicity | |
| White, n (%) | 54 (10.3) |
| Black, n (%) | 78 (14.8) |
| Hispanic, n (%) | 386 (73.2) |
HR: Heart rate. BMI: Body mass index. BP: Blood Pressure. CAD: Coronary artery disease
Figure 1 reports the frequencies of various tachyarrhythmias and bradyarrhythmias in the study cohort.
Figure 1.
Frequency of arrhythmias in the study cohort.
Values in figure are expressed as percentages.
AF: Atrial fibrillation. A/Flutter: Atrial flutter. SVT: Supraventricular tachycardia. PAC: Premature atrial contraction. VT: Ventricular tachycardia. PVC: Premature ventricular contraction. AVB: Atrial ventricular block
3.2. Supraventricular arrhythmias
AF –
AF was present 10 participants (1.9%). One additional participant (0.2%) had atrial flutter. Only 2 participants with AF (20%) were symptomatic during the AF episodes. Among those who had AF, 3 (30%) showed only 1 episode over 14 days of monitoring (lasting from 4h to 7h), 4 (40%) presented one or multiple short (<1 min) episodes, while one had AF throughout the recording, with AF burden ranging from 77% and 100% of each day.
SVT –
SVT episodes were detected in 445 participants (84.4%), although atrial tachycardia could not be excluded in 5–10% of them. Other SVT variables are reported in Figure 1. Among those who had any SVT, only 13.5% were symptomatic. SVT ≥10 beats were observed in 75 (14.2%), among which only 8 (10.7%) had symptoms.
PACs –
PACs ≥100/24h were seen in 46.9% of participants, whereas 11.2% had PACs ≥60 per hour.
3.3. Ventricular arrhythmias
VT –
Episodes of VT were observed in 132 participants (25.0%) and were symptomatic in only 14 of them (10.6%). VT with duration ≥10 beats were seen in 35 participants (6.6%), of whom only 8 (10.7%) had symptoms.
PVC –
Isolated PVCs were present in 94.6%, couplets and triplets in 49.9% and 21%, respectively. Other PVC variables are shown in Figure 1.
3.4. Bradyarrhythmias
Bradycardia –
Episodes of sinus bradycardia was observed in 491 participants (93.2%). Severity of bradycardic episodes is reported in Figure 1.
Pauses –
Sinus pauses were detected in 11 participants (2.1%).
AVB –
AVB 1st degree was observed in 31 participants (5.8%). AVB 2st degree Mobitz I was reported in 11 (2.1%). AVBs Mobitz II and 3rd degree were observed in 3 (0.6%) and 5 participants (0.9%), respectively.
3.5. Arrhythmias by sex and age
The distribution of arrhythmias by sex and age is reported in Figures 2 and 3, respectively.
Figure 2.
Frequency of arrhythmias by sex
Values in figure are expressed as percentage
*p<0.01
§p<0.001
AF: Atrial fibrillation. SVT: Supraventricular tachycardia. PAC: Premature atrial contraction. VT: Ventricular tachycardia. PVC: Premature ventricular contraction. HR: Heart rate
Figure 3.
Frequency of arrhythmias according to age (< or ≥ 75 years).
Values in figure are expressed as percentage
*p <0.05
§p <0.01
† p<0.0001
AF: Atrial fibrillation. SVT: Supraventricular tachycardia. PAC: Premature atrial contraction. VT: Ventricular tachycardia. PVC: Premature ventricular contraction. HR: Heart rate
No age or sex differences were noted for AF.
Participants ≥75 years had significantly more episodes of SVT (p=0.04), SVT ≥10 beats (p=0.03), PACs ≥100/24h (p<0.0001) and PACs ≥60/h (p<0.002) then younger ones.
Men and participants ≥75 years had significantly higher frequencies of VT (p=0.002 and p=0.005, respectively) and PVCs ≥100/24h (p=0.008 and p=0.05, respectively). More frequent episodes of VT ≥10 beats were seen in men than in women (p<0.0001).
Among bradyarrhythmias, men and participants ≥75 years had more episodes of severe bradycardia (p=0.0007 and p=0.03, respectively).
3.6. Arrhythmias by race-ethnicity
The distribution of arrhythmias by race-ethnicity is reported in Figure 4.
Figure 4.
Frequency of arrhythmias by race-ethnicity
Values in figure are expressed as percentage
* p<0.05
AF: Atrial fibrillation. SVT: Supraventricular tachycardia. PAC: Premature atrial contraction. VT: Ventricular tachycardia. PVC: Premature ventricular contraction. HR: Heart rate
The frequency of AF was greatest in whites (3/55, or 5.5%) and smallest in Hispanics (5/390, or 1.3%; p=0.03). AF frequency was intermediate in Blacks (2/76, or 2.6%), without significant differences with whites or Hispanics (p=0.41 and p=0.38, respectively). The Black subgroup was slightly older (79.1±7.7 years), but no significant age difference was present with Hispanics (76.7±6.4 years; p=0.54) or whites (77.9±7.8; p=0.38) that may have affected the results.
Whites (90.7%) and Hispanics (85.5%) had higher frequency of SVTs (90.7% and 85.9%, respectively) compared with Blacks (76.6%; both P<0.05).
Whites had more frequent VT episodes ≥10 beats than Hispanics (13.0% vs. 6.2%) and a similar trend was seen towards Blacks (13.0% vs. 5.1%), although not statistically significant (p=0.08 and p=0.11 respectively), possibly due to the smaller sample size of the white and Black subgroups.
The small number of severe bradyarrhythmias precluded sub-analyses by race-ethnicity.
3.7. Arrhythmias by presence of hypertension or diabetes
Hypertensives and diabetics showed slightly but non-significantly higher frequencies of episodes of VT than participants without these conditions (26.0% vs. 20.2% and 28.1% vs. 23.3%; p=0.27 and p=0.22, respectively).
Hypertensives had more episodes of severe bradycardia (<40 bpm) than participants without history of hypertension (13.8% vs 6%, p<0.05).
The small number of severe bradyarrhythmias precluded sub-analyses by presence of hypertension and diabetes.
3.8. Arrhythmias by electrocardiographic and echocardiographic variables
Participants with LVH or LVEF<55% had higher frequency of PAC≥100/24h (13.7% vs. 10.6% and 64.9% vs. 46.3% respectively, p<0.05 for both), SVT episodes of duration ≥15 seconds (16.7% vs. 11.0% and 24.3% vs. 11.5% respectively, p<0.05 for both) and PAC≥60/h (17.5% vs. 9.4% and 21.6% vs. 10.6% respectively, p<0.05 for both) than subjects without these conditions. Participants with LVH or LVEF<55% also had higher frequency of VT episodes (38.9% vs. 20.5% and 59.5% vs. 22.3%, p<0.001 for both), VT with duration ≥10 beats (11.1% vs. 5.0%, p=0.02; 27.0% vs. 5.1%, p<0.001) and PVC≥100/24h (42.1% vs. 30.7%, p=0.019; 59.5% vs. 31.5%, p<0.001) than subjects without these conditions.
Episodes of severe bradycardia were more common among subjects with increased LA diameter (p=0.004), LVH (p=0.012) and longer PR interval (p<0.001).
The other ECG abnormalities (prolonged QRS; prolonged QTc) were not significantly associated with any of the observed arrhythmias.
4. Discussion
The present study examined the frequency of cardiac arrhythmias in a tri-ethnic community-based cohort of older adults without overt history of AF, CHF or stroke by means of prolonged continuous cardiac rhythm monitoring. Our findings, while confirming some of the previous reports, also highlighted important differences, which only the prolonged recording allowed to unmask. A review of these aspects follows.
4.1. Supraventricular arrhythmias
AF –
Different findings about the prevalence of AF were reported depending on the population studied and the type of cardiac rhythm monitoring used (13).
Previous data about AF prevalence were mostly obtained from patients with an embolic stroke of uncertain source (14, 15). Among 590 participants without history of AF but with established cardiovascular disease, the prevalence differed largely based on the duration of cardiac monitoring moving from 1.5% for a single 10-seconds ECG to 34% for a 30-days underling the increase sensitivity with prolonged cardiac rhythm duration (16).
Conflicting information is available in general population. In two Swedish studies, the prevalence of AF was reported at 12.3% and 4.9%, respectively. In the former study, participants of age 75 years underwent intermittent 1-lead ECG recordings for 30 seconds per day over 2 weeks (17), whereas in the latter a single resting ECG was assessed at the baseline examination and after 6 years (9). However, participants with chronic AF, CHF or previous stroke were probably included (information not presented), possibly resulting in an overestimation of the frequency of AF in the general population. Recently, in the mSToPS study, among individuals at high risk of AF, the prevalence of subclinical AF was 3.9% after 4 months of recording with a home-based wearable ECG sensor patch (18). Similar numbers were observed among participants from the Multi-Ethnic Study of Atherosclerosis (MESA) and the Atherosclerosis Risk in Communities (ARIC) studies, in which after 2 weeks of monitoring the prevalence of AF/flutter was 4% and 2.5%, respectively (3, 5).
In the present study, we found AF in 1.9% of our cohort, confirming the findings from MESA and ARIC, but with some differences and additional aspects. We excluded participants with history of not only AF but also CHF and stroke, conditions associated with greatly increased AF frequency. Moreover, we examined a tri-ethnic population with an elevated proportion of Hispanics, which represent a growing and understudied minority. Finally, while ARIC only included participants 75 years of age or older, we also included younger individuals, and showed that the AF detection rate was similar at age 65–74 (5 of 198, or 2.5%) and over 75 years (5 of 329, or 1.5%; p =0.41); this observation lowers the age cutoff of interest, therefore increasing the fraction of the general population to which the study findings apply.
In our study, among participants with new onset of AF, almost half of the cases presented isolated or multiple AF episodes that were under 1 min in duration. These findings highlight the different perspective that continuous, prolonged cardiac monitoring affords compared with standard ECG or even Holter monitoring, which would have likely missed the shortest, infrequent AF episodes. Even so, AF was infrequent in our cohort, while the frequency of other atrial arrhythmias that may predispose to AF was high; the observation of AF episodes in only few of the days of recording, at times occurring late in the recording, confirms that 14 days may be too short a duration to capture the real burden of brief, asymptomatic episodes of AF in the general older population. An extension of the period of observation from 2 to 4 weeks resulted in an additional 78% detection rate in ARIC (5).
SVT –
SVT episodes, especially of short duration and without symptoms or hemodynamic instability, are considered of limited prognostic significance; however, SVT has been associated with stroke risk, independently of AF (19, 20). Also, in the Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial (ASSERT), subclinical atrial tachyarrhythmias were associated with a 5.5-fold increase in risk of future clinical AF, and with a 2.5-fold increase in risk of stroke or systemic embolism, after adjustment for other stroke predictors (21), although the definition of tachyarrhythmias chosen (190 beats per minute for at least 6 minutes) made the results applicable only to relatively prolonged episodes. Furthermore, SVT ≥10 episodes/24h was associated with presence of subclinical cerebrovascular disease in individuals free of stroke and AF history studied by 24h ECG Holter and MRI (22).
In our study, SVT, broadly defined as at least 4 PACs in a row, was present in 445 participants (84.4%). This figure is similar to that reported in MESA (88.6%) (3). Previous studies presented considerably lower frequencies; short SVT episodes were detected in 43.8% of participants in a 7-days Holter evaluation (1). The difference may be explained by the older age of our cohort (77.2±6.8 vs. 68.0±13 years) and, again, the longer duration of our recording. The possibility that some of the patients with SVT episodes may develop AF at a greater rate, or at an earlier time, than others is a hypothesis that may deserve further investigation.
PAC –
PACs are associated with future AF development and with cryptogenic stroke risk (23) (24). PACs ≥70/day and ≥100/day, based on 7-day cardiac monitoring or 24h Holter, have also been indicated as carrying a 6.6- and 11-fold increased risk of future AF development, respectively (25, 26).
Furthermore, the presence of PACs ≥100/24h was reported to be an independent predictor of future AF (HR 3.22, 95% CI 1.9–5.5) and of combined endpoint of ischemic stroke, heart failure or death (HR 1.6, 95% CI 1.04–2.44) (26).
We found ≥70 and ≥100 PACs/24h in 286 (54.3%) and 247 participants (46.9%), respectively. Of note, 59 individuals (11.2%) had PACs ≥60/h during the entire recording. Again, these figures are higher than expected, and suggest the possibility that, while AF was infrequent in our cohort, pre-AF conditions were very frequent, a circumstance that would not be appreciated without prolonged recording. The rate of conversion of atrial arrhythmias to AF, and the timing of it, are not known; our results suggest that prolonged cardiac monitoring can identify a subgroup of individuals at higher risk of AF, for whom repeat monitoring over a relatively short period of time may be indicated.
Interestingly, we also found a significantly higher frequency of supraventricular arrhythmias (PACs ≥100/day, SVT episodes of duration ≥15 seconds and PACs ≥60/h) among participants with LVH or LVEF<55%, suggesting a possible role for prolonged cardiac monitoring investigating cardiac arrhythmias among subjects with these LV abnormalities.
4.2. Ventricular arrhythmias
VT and PVCs–
VT is predominately reported in subjects with structurally abnormal heart. However, ventricular arrhythmias (VA) are also present in individuals without overt cardiovascular structural abnormalities; indeed, “idiopathic VT” accounts for 10% of all VTs (27). Furthermore, higher frequency of PVCs has been associated with subsequent decrease in LVEF and increase in incident CHF and mortality (28). According to the Rochester Epidemiology Project registry, the incidence of VA is increasing, mainly driven by an increase of idiopathic symptomatic PVCs (defined as >100 PVC/24h) (29). In 1139 participants monitored by Holter, the maximum recorded PVCs frequency was 17.7%, and that of nonsustained VT was 5.5% (28). Moreover, VT was reported in 34.6% among 439 participants after 28 days of continuous monitoring in MESA (3). In our study, the frequency of short VT episodes was 25.0%. This difference may be related to the different cohort compositions (fewer Hispanics in MESA).
In this study, we also found a significantly higher frequency of VA among participants with LVH and LVEF <55%, confirming an important link between arrhythmias and LV morphological and functional abnormalities and suggesting the importance of longer duration of cardiac monitoring in subjects with these predisposing conditions.
4.3. Bradyarrhythmias
Bradyarrhythmias, especially sinus bradycardia, are among the most common arrhythmias, and their prevalence rises with age. (6) Heart rate <60 bpm was associated with future cardiovascular diseases and death in the general population, especially in men (30). In our cohort, 93.2% had episodes of bradycardia <60 bpm and 12.5% had episodes of severe bradycardia (<40 bpm). The frequent presence of cardiac medications in this elderly cohort may have contributed to this finding.
Some data exist regarding severe bradyarrhythmias in general population. In a Swedish cohort, AVBs were found in 7% to 11% of individuals aged 72 years or older (9). Sinus pauses and high-degree AVBs were observed in 3.6% in our study. This discrepancy may be explained by differences among the cohorts (especially age and ethnicity) and method of rhythm assessment (registries versus prolonged heart rhythm monitoring). Similar to our findings, AVBs of high grade and sinus pauses were observed in 3.0% of the participants in MESA (3). Therefore, it is relevant to underline that clinically significant sinus pauses and AV blocks, which are believed to be relatively frequent in the elderly especially when cardiac rhythm is monitored at night, were not found to be so in our study, as well as in MESA; this challenges the common wisdom, and reiterates the need for prolonged monitoring to gain a more realistic understanding of the frequency of arrhythmias in the general older population.
4.4. Arrhythmias by sex and age
The existence of differences in the prevalence of arrhythmias between sexes is controversial. In ARIC, a non-significant trend toward a higher prevalence of AF in men was observed. Although no sex difference in AF prevalence was found, we observed that AF-predisposing conditions such as ≥70 PACs/24h, VAs was more common in men, as was severe bradycardia (Figure 2). An opposite result was reported in a population-based study using the Rochester Epidemiology Project database, in which the incidence of symptomatic PVCs (defined as ≥100 PVC/24 hours) was higher in women (29). However, participants in that study were younger than in ours (mean age 52.1±17.2 vs. 77.2±6.8), and the assessment of VAs was only based on medical records.
In our study, age >75 years was significantly associated with more episodes of most supraventricular and ventricular arrhythmias (Figure 3), which appear more frequent than expected in this sample of the general population of older adults; their relevance and prognostic significance remains to be established.
4.5. Arrhythmias by race-ethnicity
Some evidence suggests differences in the prevalence of arrhythmias according to ethnicity (31). In the ARIC study, AF was more prevalent in white than in African-American older adults (5.0% vs. 2.7%) using 48h ambulatory ECG (32). In our study, the frequency of AF, SVT and VT episode ≥10 beats were significantly higher in whites than in Hispanics and Blacks despite the latter group being the oldest (Figure 4). Since no significant age differences existed among race-ethnic subgroups that could have affected these results, actual race-ethnic differences appeared to exist, whose significance may warrant further investigation.
5. Strengths and limitations
Our study evaluated the frequency of cardiac arrhythmias among a sample of a multi-ethnic, community-based cohort of middle-aged to elderly subjects without history of AF, stroke or CHF. The continuous rhythm analysis for up to 14 days allowed to identify abnormalities that would have been missed with shorter recording duration. Our study also has some limitations. The demographics and risk factor profiles of our cohort may not allow the direct application of our results to populations with different risk profiles. Also, a longer recording duration may be necessary to fully evaluate the prevalence of less frequent arrhythmias in the population. Finally, the relatively limited sample size may have reduced our ability to perform analysis of subgroups of interest.
Conclusion
In a tri-ethnic cohort of older adults without known AF, CHF or prior stroke, continuous 14-day cardiac monitoring showed that the frequency of AF was low, whereas supraventricular arrhythmias that predispose to AF, such as SVT episodes and frequent PACs, were more frequent than expected. Similarly, the frequency of short VTs and PVCs was higher than expected for a sample of the general elderly population. Age, sex and race-ethnicity differences existed that may deserve further clarification.
Highlights.
Older adults free of AF, stroke or HF completed 14-days of cardiac monitoring
AF was present in 1.9%, of whom only 30% had symptoms
AF-predisposing arrhythmias were frequent, 25% had ventricular arrhythmias
Age, gender, ethnicity differences exist
Prolonged monitoring identifies subgroups that benefit from additional monitoring
Acknowledgments
The authors wish to thank Janet De Rosa, MPH (project manager), Yaritza Troche, Daysi Guerrero and Chensy Marquez (acquisition of the data).
Funding:
This work was supported by grants from the National Institute of Neurological Disorders and Stroke (grant R01 NS083784 to Dr. Di Tullio and R01 NS29993 to Drs. Sacco and Elkind).
Disclosures:
Dr. Biviano has served an advisory Boards for Boston Scientific and Biosense Webster.
Dr. Elkind reports receiving study drug in kind from the BMS-Pfizer Alliance for Eliquis and ancillary funding from Roche for the NIH-funded ARCADIA trial of apixaban vs aspirin for stroke prevention; and Dr. Elkind’s institution, Columbia University, received payments through a service agreement for his participation in analyses of study data. Dr. Elkind received no personal compensation for any of these activities. Dr. Homma reports being a consultant for St. Jude Medical, Daiichi-Sankyo, Bristol Meyers Squibb, Pfizer. Dr. Sacco has received research grants from NINDS, NCATS, AHA, Evelyn McKnight Brain Foundation and Boehringer Ingelheim.
Footnotes
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