DALLAS, October 20 -- For the first time, an implantable heart-shocking device has been used to correct atrial fibrillation, an irregular heartbeat that can lead to stroke.
Reporting in today's Circulation: Journal of the American Heart Association, Hein Wellens M.D., chairman of cardiology, Academic Hospital, Maastricht, the Netherlands, says the device, called an Atrioverter, may offer a new treatment for individuals whose hearts are prone to atrial fibrillation.
"This is the first time that an implantable defibrillator has been used to treat atrial defibrillation," says Wellens. "The defibrillator, which is the size of a beeper, can recognize irregular heart rhythms and then send an automatic shock to an atrium, one of the upper chambers of the heart, to produce a normal rhythm."
Similar implantable devices -- pacemakers and ventricular defibrillators -- have been used for decades to correct other forms of abnormal heart rhythms. A pacemaker regulates the heartbeat when the heart rate is consistently too slow by pacing both chambers of the heart to mimic normal heart function. An implantable ventricular defibrillator corrects the occasional, life-threatening erratic beating of the ventricle by rapid pacing or the delivery of a shock.
Atrial fibrillation can cause rapid heartbeat, fainting and chest pain. Eventually the rapid and irregular heartbeats can cause blood to pool in the atrium, which can lead to the development of blood clots. Clots can break free and travel into the blood vessels serving the brain, blocking them and possibly causing a stroke. According to the American Heart Association, about 15 percent of strokes occur in people with atrial fibrillation.
In an accompanying editorial, Mark E. Josephson, M.D., director of the Harvard-Thorndike Electrophysiology Institute and Arrhythmia Service, Beth Israel Deaconess Medical Center, says the financial burden imposed by atrial fibrillation is enormous, but the added cost of caring for the consequences, such as stroke, may make the device -- which costs about $15,000 -- worth the expense.
"Only about 50 percent of individuals respond to antiarrhythmic agents, but there are problems -- sometime the drugs don't work, and they have potential lethal side effects," says Josephson.
"There will probably not be one cure for atrial fibrillation, but the hope is that the more we can decrease atrial fibrillation -- through drugs or devices -- the more we will be able to prevent strokes."
The study involved implanting the defibrillators -- which are inserted under the skin -- into individuals with recurring fibrillation. Drugs to prevent the abnormal heartbeat had not been effective.
During an average eight-months follow-up, 227 spontaneous episodes of atrial fibrillation were recorded in 41 individuals -- an average of 5.6 episodes for each person. Normal rhythm was restored by the Atrioverter in 96 percent of them.
Early recurrences (those that occur within one minute of treatment) were observed in 27 percent of all treated individuals who had atrial fibrillation. These were treated with either repeated shocks, drugs or the rhythm corrected itself. The device worked in restoring normal heart rhythm in 86 percent of the time, the researchers say.
"At this point, we have demonstrated that the treatment is safe and effective," says Wellens. "But we are still at the beginning of this new approach. We need more information before the device can be considered for widespread use."
Next, the researchers will determine whether the device is safe in people with atrial fibrillation who have other heart problems.
Younger individuals with atrial fibrillation are likely to be candidates for the device because their condition tends to be more difficult to control with drugs alone, says Wellens.
A downfall of the device is that the shock given to correct the episode can be painful -- much like a thumping in the chest. Also, it's not unusual for patients to receive multiple shocks over a short period of time. The number of shocks is important, says Wellens, because of the growing discomfort as the number of shocks increases.
Co-authors are Chu-Pak Lau, M.D.; Berndt Luderitz, M.D.; Masood Akhtar; M.D.; Albert L. Waldo, M.D.; A. John Camm, M.D.; Carl Timmermans, M .D.; Hung-Fat Tse, Werner Jung, M.D.; Luc Jordaens, M.D.; and Gregory Ayers, M.D. for the Metrix Investigators.
Media Advisory: Dr. Wellens can be reached at 31 43 387 5093; fax: 31 43 387 5104; Dr. Josephson can be reached at (617) 667-4387; fax (617) 667-8769. (Please do not publish telephone numbers.)