Abstract 10726: Long-term Outcomes of Bradycardia in Adults Free of Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis (MESA)
Introduction: Asymptomatic sinus bradycardia (heart rate (HR) <60 beats per minute (BPM)) has been associated with lower cardiovascular (CVD) risk. Information is sparse, however, regarding HR <50 BPM. We assessed associations between bradycardia and incident CVD and all-cause mortality in MESA, which enrolled 6814 ethnically diverse adults aged 45-84 years without clinical CVD.
Methods: HR was obtained from 12-lead resting ECGs, which were centrally read and coded for abnormalities. Sociodemographic factors, smoking and alcohol use, vigorous physical activity, systolic blood pressure, body-mass index, creatinine, lipids, diabetes status, medication use, and coronary artery calcium were obtained by questionnaires, examination, and CT scans. Incident CVD and all-cause mortality was ascertained during median follow-up of 8.5 years. Cox proportional hazards modeling was utilized to calculate hazard ratios for HR categories (HR<50, 50-59, 60-69, 70-79, >80 BPM) adjusted for potential confounders and mediators.
Results: We excluded participants without ECGs, in atrial fibrillation, or missing outcome data (N=75 in mortality analyses). Among those remaining (mean age 62; 47% male; 38% White, 12% Chinese, 28% Black, 22% Hispanic) the mean HR was 63 BPM (SD 9.7); 6.1% had HR<50. Drugs affecting HR (chiefly beta blockers) were more common among those with HR<50 (21%), compared to HR>80 (4%). There was a lower risk of incident CVD among those with HR 50-59, but not HR<50 (TABLE). In mortality analyses, there was an interaction between HR and drugs affecting HR (p=0.004). Among those not on these drugs HR <60 BPM was associated with decreased mortality. Unexpectedly, among those on HR affecting drugs mortality was increased in HR <50 and HR 50-59 categories.
Conclusions: Sinus bradycardia is associated with a decreased incidence of CVD, however mortality was higher in those taking HR modifying drugs with HR<60 BMP. Replication of this finding in other studies is needed.
- © 2013 by American Heart Association, Inc.