A Prospective Randomized Trial of Moderately Strenuous Aerobic Exercise After an Implantable Cardioverter Defibrillator (ICD)
Background—Despite its salutary effects on health, aerobic exercise is often avoided after receipt of an implantable cardioverter-defibrillator (ICD) because of fears that exercise may provoke acute arrhythmias. We prospectively evaluated the effects of a home aerobic exercise training and maintenance program (EX) on aerobic performance, ICD shocks and hospitalizations exclusively in ICD recipients.
Methods and Results—One hundred sixty (124 men, 36 women) were randomized who had an ICD for primary (43%) or secondary (57%) prevention to EX or usual care (UC). The primary outcome was peak oxygen consumption (peakVO2), measured with cardiopulmonary exercise testing at baseline, 8 and 24 weeks. EX consisted of 8 weeks of home walking 1 hour/day, 5 days/week at 60-80% of heart rate reserve, followed by 16 weeks of maintenance home walking for 150 minutes/week. Adherence to EX was determined from exercise logs, ambulatory HR recordings of exercise, and weekly telephone contacts. UC received no exercise directives and were monitored by monthly telephone contact. Adverse events were identified by ICD interrogations, patient reports and medical records. ICD recipients averaged 55±12 years and mean ejection fraction of 40.6±15.7, all were taking beta blocker medications. EX significantly increased peakVO2 ml/kg/min (EX 26.7±7.0; UC 23.9±6.6, p=0.002) at 8 weeks, which persisted during maintenance exercise at 24 weeks (EX 26.9±7.7; UC 23.4±6.0, p<0.001). ICD shocks were infrequent (EX=4 vs UC=8), with no differences in hospitalizations or deaths between groups.
Conclusions—Prescribed home exercise is safe and significantly improves cardiovascular performance in ICD recipients without causing shocks or hospitalizations.
Clinical Trial Registration Information—ClinicalTrials.gov. Identifier: NCT 00522340.
- Received November 21, 2014.
- Revision received March 9, 2015.
- Accepted March 12, 2015.