These results were announced at a late-breaking clinical trial session at the American Heart Association's annual meeting, in Orlando, Fla., on Tuesday. The findings will be published in the Dec. 13 print issue of the New England Journal of Medicine.
Cardiac Resynchronization Therapy (CRT) devices are fixed surgically. They deliver electrical impulses to both ventricles simultaneously making both chambers contract and thereby, improving pumping efficiency.
Current guidelines agree with using CRT in patients with moderate to severe heart failure. The study aimed to see if the device could benefit patients outside those recommended parameters.
For the trial, 172 heart failure patients were randomly assigned to receive treatment with CRT or without.
Those treated with CRT showed no significant improvement in exercise capacity. This was measured by peak oxygen consumption. Some symptoms did improve, but quality-of-life scores and results of the six-minute hall walk test did not change significantly, say the researchers.
"There was no significant difference in the change in peak oxygen consumption between the treatment group and the control group during cardiopulmonary testing," says Dr. John Beshai, study lead author and director of pacemaker and defibrillator services in the division of cardiology at the University of Chicago. He added that the study was "whittling down the actual number of patients that we're treating and who are benefiting to very small numbers". Beshai has called for further research.
Previous research has suggested that CRT could help treat heart failure. This is an ailment in which the heart weakens and loses its ability to pump. About 5 million Americans suffer from heart failure. Each year, 550,000 new cases are diagnosed.