Implantable Device Physical Activity and Hospitalization for Heart Failure

Study Questions:

Do point estimates and changes in physical activity measured by cardiac implantable electronic devices correlate with all-cause mortality and heart failure (HF) hospitalizations?


The study population included Medicare beneficiaries implanted with an implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D) device (one device company) from 2007 to 2009. Daily physical activity levels and changes in levels over time were derived from implanted device accelerometers. Through linked Medicare claims data, the primary composite outcome of all-cause mortality and HF hospitalizations was obtained. Activity levels in patients with imminent events were compared to two groups: patients without events and patients with future events (at least 1 year prior). A joint model was used assess this correlation. The follow-up period was 5 years.


There were 20,927 patients included in this analysis. The median daily physical activity level was 85 minutes (interquartile range, 53.1–124.7). In patients with an imminent event, 37% were active <30 minutes/day, compared to 6% of patients without an event and 13% of patients with a future event. With respect to changes in activity, 32% of patients with an imminent event had a ≥30% reduction in activity over an 8-week period, compared to 6% of patients without an event and 8% of patients with a future event. The hazard ratio for patients having only 75 minutes of daily physical activity compared to 85 minutes was 1.13 (95% confidence interval [CI], 1.12–1.13). The hazard ratio for a within-patient decline in daily activity from 85 to 75 minutes over an 8-week period was 4.02 (95% CI, 3.82–4.22).


Lower levels of daily physical activity as determined by implanted devices correlate with increased all-cause mortality and HF hospitalizations. Significant reductions in activity level over a short period of time are associated with worse outcomes and may predict imminent events.


Promoting physical activity remains an important aspect of HF care. Also, declines in functional capacity prompt further evaluation and possibly changes in management. This study highlights another way in which clinicians can monitor for these changes, adding to self-report of symptoms and routine clinic visits. While there are some key limitations to this study including generalizability given the Medicare population and applicability in changing health outcomes, there is potential for benefit in identifying at-risk patients.

Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Exercise

Keywords: Accelerometry, Activities of Daily Living, Ambulatory Care, Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Cardiac Resynchronization Therapy Devices, Defibrillators, Implantable, Exercise, Heart Failure, Hospitalization, Motor Activity, Secondary Prevention

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