Abstract 9542: Effects of Aerobic Exercise on Biomarkers After an Implantable Defibrillator (ICD)

Abstract

Aerobic exercise reduces risk factors for CVD and improves cardiac mortality. However, the effects of aerobic exercise on cardiac function in those with an implantable cardioverter defibrillator (ICD) has not been well described. Aerobic exercise that is carried out without a signifiant increase in arrhythmias or a reduction in cardiac function would be considered safe and hold promise for prescribing exercise in this population. The purpose of this study is to describe the effects of moderate intensity aerobic exercise on B-type naturetic peptide (BNP) in those who have an ICD. Methods: Patients with ICDs (primary or secondary prevention) were randomized to either 8 weeks of aerobic conditioning exercise [home walking 1 hour/day on 5 days/week at 60-80% of maximum HR] or usual care. Usual care patients did not significantly change their level of activity during the 8 week period. Serum BNP was measured in a non-fasting state before the exercise program and again at 8 weeks. Results: 117 subjects completed baseline and 8 week follow-ups (59 usual care and 58 exercise, age 55.6±12.3; male 78%; primary prevention ICD 40%; Caucasian 83%; EF% 39.7±16; BMI 29.3±5.9). 100% of patients were taking beta blockers, 61% ACE inhibitors, 29% diuretics, 8% had DM, 40% had MI, 55% with HF, and 29% had hypertension. Overall, 83% in the exercise group met the expected total days of walking/week and 99% have met the exercise time requirement. Comparisons (mean+SD) between exercise and usual care groups on BNP at 8 weeks indicated that there was no significant difference in BNP with exercise (usual care 202.66+365.93 vs exercise 222.34+249.7, t=0.95, p=0.21). Additionally, 51% had baseline BNP values that were elevated (> 101 mg/dl). For those in the exercise group that had elevated baseline BNP levels, BNP was reduced with exercise (273+181 to 242+203). This was not true for usual care (236+165 to 250+214). A repeated measures factorial interaction test of [group x BNP level] was significant (F[1,113]=6.581, p= 0.012). Conclusions: Home walking exercise for 5 hours/week x 8 weeks in those with an ICD can be completed without significant increases in serum BNP. The level of exercise prescribed can be safely performed in patients with an ICD without significant increases in HF symptoms or BNP.