Introduction:
The Anti-Arrhythmic Effects of Exercise Trial reported that aerobic exercise training for 8 weeks after an implantable cardioverter defibrillator (ICD) significantly improved the primary outcome of cardiopulmonary function without ICD shocks or adverse events. This is a report on the longer term outcomes at 24 weeks of exercise maintenance that was continued after aerobic training.
Hypothesis:
When 8 weeks of aerobic exercise training is followed by aerobic exercise maintenance (50% reduction in the amount of walking), cardiopulmonary function [peak VO2, EX time, VO2 at AT, O2 pulse, METS, Maximum HR] will be maintained without an increase in ICD shocks or hospitalizations.
Methods:
160 subjects (80/group) with a prior ICD implant (40% primary and 60% secondary prevention), mean age 55 +12 years, 78% male, 84% Caucasian, 100% beta-blocked, and mean EF%=40%, entered a RCT comparing aerobic exercise to usual care (UC). At baseline, 8 and 24 weeks, participants completed cardiopulmonary exercise testing using a modified Balke treadmill protocol. Aerobic training= 8 weeks of home walking 1 hour/day on 5 days/week at 60-80% of maximum HR using the Karvonen formula, was followed by aerobic maintenance (EX)= 16 weeks of home walking for 150 min/week. ICD shocks and hospitalizations were verified with medical records. Analysis of variance was used to determine group x time effects on study outcomes.
Results:
Aerobic maintenance significantly increased peak VO2 ml/kg/min, p<0.000 (EX 26.9+7.7, UC 23.4+6.0), EX minutes, p<0.000 (EX 16:27+ 6:36; UC 13:24+4:33), VO2 at AT ml/kg/min, p=0.001 (EX 23.0+6.8; UC 19.8+5.8), O2 pulse p=0.01 (EX 18.7+5.5; UC 16.8+4.9), and METS, p<0.001 (EX 7.6+2.2; UC 6.7+1.8). Maximum HR was unchanged. The number of ICD shocks related to exercise was =1: 3 in UC and 1 in exercise received an ICD shock or ATP during follow-up. There were 11 hospitalizations in each group, none were related to exercise.
Conclusions:
Aerobic exercise maintenance for 16 weeks that followed aerobic exercise training for 8 weeks, maintained gains in cardiopulmonary function despite reducing the amount of walking by half (300 min vs. 150 min). Aerobic exercise in patients with an ICD is safe without increasing the number of ICD shocks or hospitalizations.
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