Exercise training and implantable cardioverter-defibrillator shocks in patients with heart failure: results from HF-ACTION (Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing)

Abstract

Objectives: The purpose of this study was to determine whether exercise training is associated with an increased risk of implantable cardioverter-defibrillator (ICD) therapy in patients with heart failure (HF).

Background: Few data are available regarding the safety of exercise training in patients with ICDs and HF.

Methods: HF-ACTION (Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing) randomized 2,331 outpatients with HF and an ejection fraction (EF) ≤35% to exercise training or usual care. Cox proportional hazards modeling was used to examine the relationship between exercise training and ICD shocks.

Results: We identified 1,053 patients (45%) with an ICD at baseline who were randomized to exercise training (n = 546) or usual care (n = 507). Median age was 61 years old, and median EF was 24%. Over a median of 2.2 years of follow-up, 20% (n = 108) of the exercise patients had a shock versus 22% (n = 113) of the control patients. A history of sustained ventricular tachycardia/fibrillation (hazard ratio [HR]: 1.93 [95% confidence interval (CI): 1.47 to 2.54]), previous atrial fibrillation/flutter (HR: 1.63 [95% CI: 1.22 to 2.18]), exercise-induced dysrhythmia (HR: 1.67 [95% CI: 1.23 to 2.26]), lower diastolic blood pressure (HR for 5-mm Hg decrease <60: 1.35 [95% CI: 1.12 to 1.61]), and nonwhite race (HR: 1.50 [95% CI: 1.13 to 2.00]) were associated with an increased risk of ICD shocks. Exercise training was not associated with the occurrence of ICD shocks (HR: 0.90 [95% CI: 0.69 to 1.18], p = 0.45). The presence of an ICD was not associated with the primary efficacy composite endpoint of death or hospitalization (HR: 0.99 [95% CI: 0.86 to 1.14], p = 0.90).

Conclusions: We found no evidence of increased ICD shocks in patients with HF and reduced left ventricular function who underwent exercise training. Exercise therapy should not be prohibited in ICD recipients with HF. (Exercise Training Program to Improve Clinical Outcomes in Individuals With Congestive Heart Failure; NCT00047437)

Figure 1

Multivariable predictors* of ICD shocks in patients with symptomatic HF and LVEF≤35%. The forest plot shows the hazard ratios for the occurrence of ICD shocks after accounting for other prognostic factors. Exercise training was not associated with an increased hazard of shock (p=0.45). *Exercise induced dysrhythmia was defined as a cardiopulmonary exercise test stopped for reason of serious arrhythmia, or frequent ventricular ectopy occurred either during CPX test or during recovery.

Figure 2

Adjusted (predicted) shock-free survival in patients with ICDs at baseline in the HF-ACTION trial according to randomized treatment (exercise training plus usual care vs. usual care alone). After adjustment for the identified predictors of shock, exercise training was not associated with the occurrence of ICD shocks (HR 0.90 [0.69-1.18], p=0.45). The adjusted (predicted) shock-free survival according to exercise therapy versus usual care is shown.