Introduction: Exercise improves outcomes across a broad spectrum of cardiovascular disease. The optimal design, safety, and effectiveness of exercise-based interventions in ICD and CRT patients remain poorly understood.
Methods: We performed a Pubmed search for clinical studies using the following search terms: “implantable cardioverter-defibrillators”; “ICD”; “cardiac resynchronization therapy”; “CRT”; and any one of the following: “activity”; “exercise”; “training”; or “rehabilitation”; from 1/1/2000 - 10/1/2015. Eligible studies were evaluated for study design features, measured endpoints, and reports of ICD shock rates.
Results: From 649 articles, 75 abstracts met initial criteria from which 16 studies remained after full-text review: 56% randomized trials, 31% single-arm trials, 13% observational studies. A total of 2114 patients (median 52, range, 8 - 1053) were included. Exercise interventions varied widely in character and duration (mean days 82.6, range 23 - 168). VO2 max and other physiologic exercise performance measures were the most common primary endpoints (81%), with few studies evaluating clinical outcomes. Most studies (75%) showed statistically significant improvement in primary physiologic endpoints. ICD shocks were uncommon during active exercise intervention with only 7 shocks in 1248 patients. ICD shocks in follow-up were less common in patients receiving exercise intervention (16.9% v 25.6%, Figure).
Conclusion: Exercise training in patients with ICDs and CRT appears safe and effective based on a small literature. Lack of consensus on design and both physiologic and clinical endpoints limit broader application to an important patient population.