Harvard Heart Letter

Heart Beat: Exercise no trigger for defibrillator shocks

A carefully tailored exercise plan can strengthen a failing heart while keeping its owner out of the hospital and living longer. Does this apply to the growing number of people with heart failure who have a defibrillator (ICD) implanted, or does exercise cause these devices to deliver unnecessary shocks as the heart speeds up during exercise?

The HF-ACTION trial compared a structured exercise plan against generic advice to exercise among 2,331 men and women with heart failure. At the end of the two-year trial, fewer people in the exercise group had died of cardiovascular disease or were hospitalized for their heart failure. Among the 1,053 volunteers who had an ICD, 20% in the exercise group had received at least one shock from their device, compared to 22% in the exercise-advice group (American College of Cardiology meeting, March 15, 2010). Shock rates were slightly higher in volunteers with atrial fibrillation, atrial flutter, or ventricular tachycardia.

The take-home message from the study: don't shy away from exercise just because you have an ICD.

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