With Implantable Cardioverter-Defibrillators, Every 10-Minute Increase in Physical Activity Reduces Mortality Risk by 1.1%

Brett Atwater, MD

New research from a study of Medicare beneficiaries is underlining the importance of early increases in physical activity, whether through structured rehabilitation or at-home programs, among patients who recently received an implantable cardioverter-defibrillator (ICD).

An analysis of more than 42,000 patients who had ICDs implanted from 2014-2016, results suggest every 10 minutes in daily physical activity was associated with a 1.1% reduction in all-cause mortality and a 1.0% reduction in risk of heart failure hospitalization at 1-year.

“This finding helps confirm prior research showing that cardiac rehabilitation is underutilized, and the benefits of increased physical activity obtained in cardiac rehabilitation programs also may be achievable at home, potentially offering another opportunity to improve outcomes in patients with ICDs,” said study author Brett D. Atwater, MD, director of electrophysiology and electrophysiology research at Inova Heart and Vascular Institute, in a press release from the American Heart Association.

Despite specific inclusion in major guidelines, cardiac rehabilitation is underutilized, not just in patients with ICDs, but across a spectrum of cardiovascular conditions. With an interest in adding to the growing evidence base supporting use and to push for increased access to these programs, Atwater and colleagues from the Duke University School of Medicine sought to assess the association between physical activity and participation in cardiac rehabilitation programs with risk of death or heart failure hospitalization following ICD implantation.

Investigators designed their study as a retrospective observational study of Medicare beneficiaries who underwent ICD implantation from January 1, 2014, to December 31, 2016. Using Medicare claims data accessed through the Centers for Medicare and Medicaid Services Virtual Research Data Center, investigators identified 41,631 patients who underwent ICD implantation during the period of interest.

Of note, all patients included in the study had a history of heart failure and coronary artery disease. Patients were excluded if they were enrolled in Medicare for fewer than 12 months prior to index date, if they participated in their first rehabilitation sessions less than 30 days or more than 365 days after implantation.

For the purpose of analysis, participation in cardiac rehabilitation was deranged as having at least one Medicare carrier claim or outpatient claim occurring between 30 and 365 days after ICD implantation. The primary outcome of interest was all-cause mortality and the secondary outcome of interest was hospitalizations for heart failure.

The study cohort had a mean age of 75 (SD, 10) years, 72.3% were male, and the mean baseline physical activity level was 128.9 (SD, 78.4) minutes per day. At 3 years of follow-up, 25.1% of patients in the study cohort had died and 51.7% experienced a heart failure-related hospitalization. Of the 41,731 patients included in the study, only 1324 (3.2%) met the criteria for being considered cardiac rehabilitation participants. Compared to nonparticipants, participants were more likely to be white (91.0% vs 87.3%), male (75.5% vs 72.2%), and more likely to have diabetes (48.8% vs 44.1%), ischemic heart disease (91.4% vs 82.1%), and congestive heart failure (90.4% vs 83.4%).

Among those who participated in cardiac rehabilitation, the median number of sessions was 24 (955 CI, 2-36). Data indicated daily mean physical activity levels increased by 9.7 (SD, 57.8) minutes per day. In contrast, physical activity levels decreased by a mean of 1.0 (SD, 59.7) minutes per day among nonparticipants (P <.001).

In adjusted analysis, cardiac rehabilitation participants had a 24% lower risk of 1- to 3-year mortality compared to nonparticipants. Further analysis accounting for ICD measured change in physical activity, no differences were observed in mortality with or without cardiac rehabilitation.

Further analysis suggested every 10 minutes of increased daily physical activity during the study period was associated with a 1.1% reduction ion in risk of death at 1-year (HR, 0.989; 95% CI, 0.979-0.996; P <.001). A similar trend was seen for risk of heart failure hospitalization, with every 10-minute increase in daily physical activity associated with a 1% reduction in risk (HR, 0.99; 95% CI, 0.986-0.995; P <.001).

“Our study examined whether physical activity outside of a formal cardiac rehabilitation program could yield similar benefits, and we found it did,” said Atwater. “This suggests that additional options like home-based cardiac rehabilitation might help more patients realize the health benefits of increased physical activity.”

This study, “Early Increased Physical Activity, Cardiac Rehabilitation, and Survival After Implantable Cardioverter-Defibrillator Implantation,” was published in Circulation: Cardiovascular Quality and Outcomes.