The patient is sedated but awake and is given a local anesthetic at the site of insertion. The defibrillator sends a small shock to the heart's upper chambers when atrial fibrillation occurs, correcting the rhythm abnormality before clots can form. However, drugs aren't always effective. University Hospitals of Cleveland is one of only three U.S. sites studying the implantable atrial defibrillator. Defibrillators that are implanted in the heart's lower chambers, or ventricles, have already been approved by the Food and Drug Administration.
Ventricular fibrillation is life-threatening but affects a relatively small percentage of people.