June 2004
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Dual pacing proves vital COMPANION in heart failure
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| Douglas Mann, MD, (right) discusses lab results with post-doctoral student Sandra Haudek PhD |
The use of a pacemaker to electrically stimulate and synchronize the contractions of the right and left ventricles, or pumping chambers of the heart, significantly improves the quality and length of life of a patient with heart failure, said a Baylor College of Medicine expert who participated in a large, national study.
When the pacemaker is combined with an implanted defibrillator, which automatically shocks a faltering heart back to life, it can also significantly reduce the rate of death from heart failure, according to the results of the Comparison of Medical Therapy, Pacing and Defibrillation in Chronic Heart Failure or COMPANION trial. The results of the study appeared in a recent issue of The New England Journal of Medicine (N Engl J Med. 2004;350:2140-2150).
The study evaluated the effectiveness of cardiac resynchronization therapy with pacemakers and implantable cardiac defibrillators to reduce the risk of mortality and hospitalization in advanced heart failure patients.
Heart failure epidemic
Many experts consider heart failure a nationwide and even worldwide epidemic. An estimated five million people in the United States suffer from this disorder. The COMPANION trial dealt with those whose disease was the most serious.
Heart failure occurs when the pumping chambers of the heart are damaged or unable to do their jobs efficiently. Among the causes of this disorder are clogged coronary arteries that prevent adequate flow of blood to the heart muscle, high blood pressure, heart attack, diabetes, weakening of the heart muscle, heart valve disorders or infections, heart disease that occurs at birth, severe lung disease or infection of the sac that contains the heart (the pericardium).
In approximately 30 percent of heart failure patients, the walls of the main pumping chamber called the left ventricle are out of synch. In other words, they do not pump in unison, which reduces the effectiveness of the ventricle significantly. The dual-chambered or biventricular pacemaker is designed to get the walls pumping in unison again. They resynchronize the heart. While single-chambered pacemakers work only on the right side of the heart, the biventricular models work on both. By stimulating the left and right ventricles at the same time, they enable the critical left ventricle to work more efficiently. Some biventricular pacemakers come with an implantable cardioverter defibrillator that is designed to shock the heart back into an appropriate rhythm when it stops pumping.
Douglas Mann, MD, BCM professor of medicine, and Guillermo Torre-Amione, MD, BCM associate professor of medicine, took part in the nationwide study. The Houston physicians treated 25 patients with the most advanced stages of heart failure.
“The COMPANION trial is a landmark clinical trial that will change the way we manage patients with heart failure, now and in the future,” said Mann, also director of the Winters Center for Heart Failure Research at BCM. “The results of this study are the first to show that resynchronization therapy of the heart by pacing the heart from two different sites is vastly superior to our current best medical therapy for heart failure.”
More than 1,600 patients
The multi-center COMPANION Trial included more than 1,600 heart failure patients from across the country. While previous clinical studies show that resynchronization devices improve physical function and quality of life only, the COMPANION Trial was the first to evaluate the effect of the pacemaker for both chambers combined with a implantable defibrillator and to show that the devices can decrease the risk of death. In this study, all patients received the best possible medical treatment.
One group of patients received only the drug treatment. Another group received the dual-chamber pacemaker and a third group received the dual chamber pacemaker combined with the implantable defibrillator.
When the researchers designed their study, they decided that the major factor they would measure would be a combination of death from all causes or hospitalization for any reason. In the COMPANION study, there was a reduction of 19 percent in this combined factor in patients who received the dual-chambered pacing alone and a 20 percent reduction in those who received the dual-chambered pacing plus an implantable defibrillator. The reductions were in comparison to the statistics found in patients who received only medical therapy.
When only death from all causes was considered, the rate in the group that received the dual-chambered pacemaker was 24 percent lower than that in the medical treatment alone group. The difference was marginally statistically significant, according to the study’s authors. The group that received dual pacing plus the implantable defibrillator had a 36 percent reduction in death compared to the medicine alone group – a finding that was statistically significant.
Patients with moderate to advanced heart failure should consult their physicians if they are candidates for this new therapy.
This trial was conducted by a team of BCM investigators headed by Mann and Torre-Amione, also medical director of the cardiac transplant service at Baylor and The Methodist Hospital. Other BCM investigators include Biykem Bozkurt, MD, associate professor of medicine and Anita Deswal, MD, Vinay Thohan, MD, and Michael Koerner, MD, all assistant professors of medicine.
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