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Release: April 12, 1999

UI studying new defibrillator to treat atrial fibrillation

IOWA CITY, Iowa -- Researchers at the University of Iowa are leading a nationwide clinical study of a new defibrillator, a device that uses electric shock to restore normal heart rhythm. Cardiologists will use the biphasic defibrillator in non-emergency situations to reset the irregularly beating hearts of patients with atrial fibrillation.

The clinical study compares the new biphasic, or two-pulse, defibrillator with the standard, single-pulse difibrillator, said Richard E. Kerber, M.D, UI professor of internal medicine and associate director of the Division of Cardiology. Kerber is principal investigator of the Iowa-led study, which includes 11 other medical centers. The study is double-blind and randomized, meaning neither the patient nor the physician will know whether the standard or biphasic defibrillator is used until after the fact.

"We will use the new device for patients in whom the upper two chambers of the heart are not beating regularly, but are in atrial fibrillation, a condition of disorganized electrical function and an irregular, less effective heart beat," Kerber said.

He emphasized that the UI will continue to use standard defibrillators in any emergency situation involving a patient with cardiac arrest, in which ventricular fibrillation occurs. In those cases, the lower chambers of the heart quiver ineffectively.

A defibrillator sends an electrical pulse that momentarily stops the heart's irregular, disorganized electrical activity, Kerber explained. The extremely brief pause then allows the heart to begin beating again in a normal rhythm.

A standard defibrillator delivers a single spike of electrical current. The biphasic defibrillator delivers two spikes, a positive pulse followed by a negative pulse. It also uses substantially less energy than a standard defibrillator.

He added that patients with atrial fibrillation often know when they need to seek treatment. "These patients have an irregular heartbeat and feel other symptoms typically associated with heart conditions, such as shortness of breath or palpitations," he said. The condition is usually not life threatening.

After receiving treatment for atrial fibrillation, patients usually may return home within one to two hours.

Kerber said the biphasic waveform is already used in automated defibrillators to treat ventricular fibrillation. These emergency devices are increasingly found on airlines and in places, such as hotels, where large numbers of people gather. Kerber served as chair of an American Heart Association task force to promote the use of these automated defibrillators.