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)

Study Questions:

What is the effect of exercise training on the risk of implantable cardioverter-defibrillator (ICD) therapy in patients with heart failure (HF)?


HF-ACTION (Heart Failure: 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.


The investigators 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], 1.47-2.54), previous atrial fibrillation/flutter (HR, 1.63; 95% CI, 1.22-2.18), exercise-induced dysrhythmia (HR, 1.67; 95% CI, 1.23-2.26), lower diastolic blood pressure (HR for 5 mm Hg decrease <60, 1.35; 95% CI, 1.12-1.61), and nonwhite race (HR, 1.50; 95% CI, 1.13-2.00) 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, 0.69-1.18; 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, 0.86-1.14; p = 0.90).


The authors concluded that there was no evidence of increased ICD shocks in patients with HF and reduced left ventricular function who underwent exercise training.


This study reported that exercise therapy is not associated with an increase in all-cause ICD shocks. Furthermore, ventricular arrhythmias induced during exercise testing are associated with ICD shocks; therefore, exercise testing may be useful in ICD patients before beginning a structured exercise program. Based on these data, exercise therapy should not be prohibited in ICD recipients with HF for fear of inducing ventricular dysrhythmias that precipitate ICD firing, and may actually be helpful in screening patients at increased risk for exercise-associated shocks.

Keywords: Ventricular Function, Left, Shock, Ventricular Fibrillation, Blood Pressure, Heart Diseases, Tachycardia, Ventricular, Exercise Therapy, Heart Failure, Stroke Volume, Confidence Intervals, Hospitalization, Defibrillators, Implantable

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