A couple of old standbys鈥攄efibrillators and pacemakers鈥攁re reducing the risk of death by up to 40 percent in people whose hearts don't pump enough blood, say 人妻中出视频 of Utah cardiologists who participated in a nationwide trial of a new generation of the devices.
Results of the trial, which tested new-generation pacemakers, defibrillators, and a combination of both to "resynchronize" heart rhythms, will change the standard of care for thousands of congestive heart failure patients, according to the U physicians.
The trial was conducted with patients who have weakened hearts, also called low ejection fraction, and bundle branch block, a condition that prevents the ventricles from contracting synchronously and reduces the amount of blood they pump.
Pacemakers are used to speed up heartbeats, while defibrillators shock hearts back into normal rhythm when they are beating too fast. Defibrillators appear to be particularly effective in saving lives of people with low ejection fraction.
"Defibrillation therapy should be strongly considered in most patients with weak hearts," said Edward M. Gilbert, M.D., a cardiologist and professor of internal medicine who was the U's principal investigator in the trial. "This device will reduce the risk of death."
Roger Freedman, M.D., professor and acting chief of the Division of Cardiology in the School of Medicine, served as the trial co-investigator at the U of U.
The trial, called COMPANION-Comparison of Medical Therapy, Pacing, and Defibrillation in Chronic Heart Failure-randomly tested 1,600 congestive heart failure patients nationwide, 20 of them in Utah. Trial participants were split into three groups. Twenty percent received medication, 40 percent received pacemakers, and 40 percent received combination pacemaker/defibrillators.
The trial began in January 2000 and had been scheduled to run three years, but ended in November after the results showed significant reductions in the risk of death for patients who received pacemaker/defibrillators or pacemakers.
Compared with patients who received medication only, those with the combination pacemaker/defibrillator experienced a 40 percent reduction in the risk of death or hospitalization. Patients who received pacemakers experienced a 20 percent reduction in the risk of death or hospitalization.
Trial participants had severe congestive heart failure and had been hospitalized at least once in the prior 12 months.
Gilbert likens the delay in the heart's electrical signal to a car engine with its timing off. Biventricular pacemakers help correct that by restoring the sequence of contraction and improving the amount of blood ejected with each beat.
Devices used in the trial were the CONTAK TR pacemaker and CONTAK CD pacemaker/defibrillator made by Guidant Corp. The CONTAK devices have three wires that connect to the heart, compared with other pacemakers and defibrillators that have two wires. The third wire restores the synchrony of heart muscle contraction by allowing the electrical signal to be conducted simultaneously to both sides of the heart.
Although the extent to which these new devices will be applied is not yet known, Freedman has no doubt many of the nation's 5 million congestive heart failure patients could benefit from them.
"This is going to have a major impact," he says.
But the trial results don't mean all weak heart patients should receive a defibrillator or pacemaker immediately. First, they should take medication, and if that doesn't work, then a defibrillator, pacemaker, or combination could be implanted, according to Freedman.
At the U, Freedman and John D. Day, M.D., cardiologist and assistant professor of internal medicine, implant the devices.