NEW YORK, April 15 (Reuters) -- A clinical trial comparing the effectiveness of drugs versus implantable cardiac defibrillators in the treatment of life-threatening arrhythmias -- or abnormal heart rhythms -- has been stopped.
The National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health announced the decision Monday after it became clear that there was a significant reduction in deaths among patients with arrhythmia who had a defibrillator implanted in their chests.
"This landmark study is the first large, controlled study to show that implantable cardiac defibrillators improve overall survival in patients with serious ventricular arrhythmias," said Dr. Claude Lenfant, NHLBI director. "We've known for some time that these devices stop arrhythmias and restore normal heart rhythm, but it has not been known -- until now -- whether they improve overall survival."
Since 1993, more than 1,000 patients in the U.S. and Canada have participated in the Antiarrhythmics Vs. Implantable Defibrillators (AVID) trial. The goal of the study was to determine which strategy offered the greatest reduction in mortality for patients with a history of ventricular fibrillation (VF) -- where the rhythm of the heart beat is lost -- or serious ventricular tachycardia (VT) - where the heart beats too fast. Of the estimated 350,000 sudden cardiac deaths in the U.S. each year, most are thought to be due to VF and VT, according to NIH data.
In VF, the ventricles quiver chaotically, preventing blood from being pumped out and depriving the body and brain of oxygen. In VT, rapid electrical impulses cause the heart to beat too fast, decreasing blood flow and depriving the body of oxygen.
Patients enrolled in the AVID trial, average age 65 years, were randomly assigned to receive treatment with either a drug (amiodarone or sotalol), or with a defibrillator. Unlike drugs, defibrillators are not designed to prevent arrhythmias from starting. Instead, they attempt to restore the heart's normal rhythm by pacing the heart or delivering an appropriate electric shock. The devices can also store information on the heart rhythm so it can be assessed by the patient's doctor.
After one year, patients with implanted defibrillators experienced a nearly 38% reduction in deaths compared with the group of patients taking an antiarrhythmic drug, the NIH said. In years two and three of the study, there was a 25% reduction in deaths in the defibrillator group.
"Even though the relative benefit for implantable defibrillators compared to drugs declined over time," said Lenfant, "the difference between the two treatment strategies -- even at three years -- was still very significant. If we apply the results of AVID to the population at risk, over 1,000 lives would be saved each year in the U.S."
Dr. Douglas Zipes, chair of the AVID Steering Committee, believes the results of this study will "streamline" the approach physicians use for treating patients with life-threatening arrhythmias.
"It is clear that these patients should be treated first with an implantable cardiac defibrillator," he said, noting that the devices are "like having an emergency room implanted in your chest."
Patients with ventricular fibrillation or ventricular tachycardia who are being treated with an antiarrhythmic drug are advised to talk to their doctor about an implantable defibrillator.
According to AVID data, the cost of implanting a defibrillator averages $66,600 -- nearly twice as much as the average cost of monitoring a patient in the hospital who is receiving antiarrhythmic drugs ($34,000). The AVID investigators speculate that defibrillator therapy will become less costly over time, and are currently evaluating the cost-effectiveness and quality of life associated with both strategies.
