1. Second Division of Cardiology, Evangelismos General Hospital, GR-11526 Athens, Greece;
2. Department of Physiology, Michigan State University, East Lansing, Michigan 48824;
3. Division of Cardiology, MetroHealth Medical Center/Case Western Reserve University, Cleveland, Ohio 44106;
4. Department of Medicine, University Medical Center, Stony Brook 11794; and
5. Veterans Affairs Medical Center, Northport, New York 11772