Abstract 3090: Exercise After an ICD Improves Cardiorespiratory Fitness and Heart Rate Variability
Exercise is often not prescribed for patients who have an implantable cardioverter defibrillator (ICD) because patients are fearful of receiving an ICD shock with exercise, and providers are unsure how to prescribe exercise in this population.
Purpose: The purpose of this study was to determine the impact of an aerobic exercise program on cardiorespiratory fitness and heart rate variability (HRV) after sudden cardiac arrest and ICD implantation.
Methods: A single group 8-week pre-post test design within 6 months after receiving an ICD was used. Aerobic exercise consisted of treadmill and home walking for 5 hours/week at 60 – 80% of peak maximal oxygen uptake (V02) for 8 weeks. Exercise took place 3 hours a week in a supervised outpatient rehab setting, with home walking 2 hours/week documented with a Polar Heart Rate Monitor with recording capability. Outcomes:
cardiorespiratory fitness [peak V02, exercise time, V02 at anaerobic threshold (AT), 02 pulse (V02/HR), mean heart rate (HR)], and
HRV [24 hour holter monitor: time and frequency domain measures].
Results: Ten patients with an ICD for secondary prevention of cardiac arrest, mean age 54.3±10 years, Caucasian (100%), male (90%), mean EF% = 39.9±21, & taking beta blocker medication (100%) completed 8 weeks of exercise. Using paired t-tests, significant improvements were noted in cardiorespiratory fitness [02 pulse, p = 0.05; V02 at AT, p = 0.05; mean HR, p = 0.04] and HRV [standard deviation of all R-R intervals (SDNN), p = 0.02; High frequency power, p = 0.02]. Trends for improvement were demonstrated in other fitness measures (exercise time, peak V02, METS) and HRV measures (standard deviation of 5 minute segments (SD5 min), low frequency (LF) power, total power). There were no hospitalizations related to the exercise program. There were no ICD shocks during exercise testing.
Conclusion: Aerobic exercise, strenuous enough to improve cardiorespiratory fitness and HRV, is safe and feasible to implement in those with an ICD. Future research should test exercise programs that can be implemented in the home setting. Even with a small sample size, this is one of the first reports to demonstrate safety and feasibility in implementing aerobic exercise in patients who have complex cardiac arrhythmias and an ICD.