Defibrillators can increase heart failure risk

NEW YORK, June 14 (Reuters) Implanted cardioverter-defibrillators (ICDs) can improve the survival rates of carefully selected patients with chronic heart disease by 30 per cent to 54 per cent. However, investigators have found that ICDs also appear to increase the risk of heart failure.

ICDs are recommended for patients who have had a near-fatal episode of irregular heart rhythm, also referred to as an arrhythmia, and who have a high risk of another episode. The devices are designed to detect arrhythmias, where the heart beats too slowly or too rapidly, and to deliver a shock to restore normal rhythm.

Dr Ilan Goldenberg, at the University of Rochester Medical Center in New York, and his associates reviewed the records of 1,197 patients who had an ICD. The investigators analyzed the factors associated with the progression to heart failure.

The patients had experienced a heart attack at least one month before receiving the ICD and had a weaken ability to pump blood from the heart, according to the report in the medical journal Circulation. Included were patients assigned to receive drug therapy only, a single chamber ICD or a dual chamber ICD.

The researchers found that the rate of hospitalisation for heart failure was higher among those with single chamber ICDs (22.4 per cent) and dual-chamber ICDs (24.9 per cent) compared with patients in the conventional drug therapy group (17.4 per cent).

Nevertheless, survival was increased by the ICDs, and was similar before and after a first heart failure event in patients who received the single-chamber ICD group. However, those who received the dual-chamber ICD had significantly worse survival rates after a heart failure event.

''The increased risk of heart failure among patients allocated to the ICD group was related to the life-prolonging effect of appropriate defibrillator shocks,'' Goldenberg's team suggests.

The investigators conclude that prevention of heart failure progression is vital after ICD implantation. One way to achieve this, they suggest, is through cardiac resynchronization therapy, along with drug therapy that includes a beta-blocker.

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