April 8, 2013 – Jonathan Piccini, MD, MHS, leads study which found no evidence of an increase in implantable cardioverter-defibrillator shocks for patients undergoing exercise therapy.
A recent study has found that patients with heart failure (HF) and reduced left ventricular function who have an implantable cardioverter-defibrillator (ICD) are not at any increased risk when they undergo exercise therapy. An ICD (similar to a pacemaker) is a small, battery-powered electrical impulse generator used to detect cardiac arrhythmia and correct it by delivering a jolt of electricity to the heart. Researchers found no evidence of an increase in these ICD shocks in patients undergoing exercise therapy.
The HF guidelines developed by the American College of Cardiology and American Heart Association recommend exercise training because of its proven health benefits. However, because exercise increases catecholamine and can provoke both ventricular and supraventricular arrhythmias, which can lead to appropriate and inappropriate ICD shocks, patients often express concern about the safety of exercise therapy. Earlier studies that examined this issue were limited by their retrospective nature, small sample sizes, and limited power. This most recent analysis drew its data from the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION) trial.
The DCRI’s Jonathan Piccini, MD, MHS, was lead author for this study, which also received contributions from William Kraus, MD; Adrian Hernandez, MD, MHS; James Daubert, MD; and Christopher O’Connor, MD. The study randomized 2,331 outpatients with HF and an ejection fraction ≤35 percent to exercise training and usual care or usual care alone. The study was published in the April addition of the Journal of American College of Cardiology: Heart Failure. The researchers used Cox proportional hazards modeling to examine the relationship between exercise training and ICD shocks.
The data showed no significant difference in the number of ICD shocks in the two randomized groups and also showed that improvements in cardiopulmonary capacity are preserved in patients with ICDs. The researchers suggest that exercise testing be used to evaluate a patient’s candidacy for exercise training, as the analysis also showed that patients with evidence of exercise-induced dysrhythmia had a 67 percent higher risk of ICD shocks.