Adherence to an Aerobic Exercise Intervention after an Implantable Cardioverter Defibrillator (ICD)

Exercise adherence is an important element in achieving important exercise outcomes. The purpose of this study was to describe adherence in a home-based aerobic exercise program following an implantable cardioverter defibrillator (ICD), determine effects of adherence on peakVO2 , and outline reasons for nonadherence.

A single-blind randomized control trial of home walking compared to usual care in 160 patients with an ICD for primary or secondary prevention was conducted. This report is on adherence in the exercise arm (N = 84). Home walking exercise consisted of 8 weeks of aerobic conditioning (60 minutes/day, 5 days/week) followed by 16 weeks of aerobic maintenance (150 minutes/week, 30 minutes/session) at 60-80% of heart rate reserve. Adherence was tracked using Polar heart rate (HR) monitors, pedometers, home exercise logs, and telephone follow-up. Adherence was defined as performing at least 80% of prescribed exercise. For aerobic conditioning, there was a mean frequency of 3.81 walks/week, duration of 1,873 minutes walked, and 17.5% of exercise was in the target HR (THR) zone. For aerobic maintenance, there was a mean frequency of 2.4 walks/week, duration of 1,872 minutes/walked, and 8.7% of exercise was in the THR zone. Those who were 80% adherent achieved a 3.4 mL/kg/min (P = 0.03) improvement in peakVO2 over those who were <80% adherent. Reasons for nonadherence to exercise ranged from scheduling issues to viral illness and fatigue.

Adherence to aerobic exercise frequency and duration was high with few dropouts, resulting in higher peakVO2 . Exercise monitoring equipment encouraged adherence and conferred a sense of safety to exercise.