Implantable Defibrillators Save Lives But May Increase Heart Failure Risk

"Some patients whose lives were prolonged by ICDs were sicker and more prone to develop heart failure," said Ilan Goldenberg, M.D., research assistant professor at the University of Rochester Medical Center and lead author of the latest report from the Multicenter Automatic Defibrillator Implantation Trial-II (MADIT-II). "The ICD kept them alive by preventing sudden cardiac death as their heart disease naturally progressed to heart failure.

"Patients who developed heart failure had almost four times the increase in risk of death during follow up. This study should direct more attention to the prevention of heart failure in patients receiving an ICD."

The MADIT-II trial included 1,232 heart attack patients with an ejection fraction of 30 percent or less who had a heart attack at least a month before enrollment. Researchers randomly assigned patients to ICD (single or dual chamber) or best medical care.

Ejection fraction is a measure of the heart's ability to efficiently pump blood to other parts of the body. An ejection fraction of 60 percent is healthy, so the MADIT-II patients were pumping blood at about half the rate of healthy people.

Compared to patients who received only medical therapy after a heart attack, those who had ICDs implanted were 39 percent more likely to have a first hospitalization for heart failure and 58 percent more likely to be hospitalized for recurrent heart failure during an average 20-month follow up.

The overall survival benefit was 42 percent for patients who received a single chamber ICD and 51 percent for those with a dual chamber. Researchers analyzed data from 1,224 study patients, including 402 who received single-chamber devices and 313 who were implanted with dual-chamber devices.

Twenty-three percent of patients who received ICDs in the MADIT-II trial were hospitalized for HF during 20 months of follow-up versus 17 percent of patients who received only medical therapy.

Patients who received single-chamber devices did not suffer a reduced survival benefit if they developed heart failure. However, patients who were implanted with dual-chamber devices had a significant reduction in survival benefit after heart failure, Goldenberg said.

Resynchronization therapy with a biventricular ICD is currently being evaluated as a preventive strategy to reduce the risk of heart failure in ICD treated patients in a follow-up study to MADIT-II, he said.

Co-authors are Arthur J. Moss, M.D.; W. Jackson Hall, Ph.D.; Scott McNitt, M.S.; Wojciech Zareba, M.D., Ph.D.; Mark L. Andrews, B.B.S.; and David S. Cannom, M.D.

MADIT-II was funded in part by Guidant Corporation.