Early Increased Physical Activity, Cardiac Rehabilitation, and Survival After Implantable Cardioverter-Defibrillator Implantation

Background: Increased physical activity (PA) through cardiac rehabilitation (CR) improves outcomes in patients with heart failure and coronary disease, but CR referral remains infrequent. Implantable cardioverter-defibrillators (ICDs) can provide daily PA measurements to patients that may motivate them to increase PA, but it remains unclear if increased ICD measured PA is associated with improved outcomes with and without CR. Methods: This is a retrospective observational study of 41 731 Medicare beneficiaries with ICD implantation between January 1, 2014 and December 31, 2016. We linked daily ICD PA measurements and Medicare claims data to determine if increased PA is associated with a reduction in the likelihood of death or heart failure hospitalization. To determine if CR participation altered the effect of PA on outcomes, we performed two additional analyses matching CR participants and nonparticipants using propensity scores. The first match included demographics, comorbidities, and baseline PA measurements. The second match also included the change in PA measured during CR or the same time frame after ICD implant among nonparticipants. Results: The mean age was 75 (SD, 10) years, 30 182 beneficiaries (72.3%) were male, and 1324 (3%) participated in CR. Increased ICD detected PA was associated with improved survival. CR participants had a mean PA change of +9.7 (SD, 57.8) min/d, whereas nonparticipants had a mean change of -1.0 (SD, 59.7) min/d (P<0.001). After matching for demographics, comorbidities and baseline PA, CR participants had significantly lower 1- to 3-year mortality (hazard ratio, 0.76 [95% CI, 0.69-0.85], P=0.03). After additionally matching for the ICD measured change in PA during CR there were no differences in mortality with and without CR (hazard ratio, 1.00 [95% CI, 0.82-1.21], P=0.87). Every 10 minutes of increased daily PA was associated with a 1.1% reduction in all-cause mortality in both groups. Conclusions: Among Medicare beneficiaries with ICDs, small increases in PA were associated with significant reductions in all-cause mortality.