1. From the Department of Cardiological Sciences, St. George's Hospital Medical School (A.J.C.), and the Department of Cardiology, Royal Brompton National Heart and Lung Hospital (C.J.G.), both in London. Address reprint requests to Dr. Camm at the Department of Cardiological Sciences, St. George's Hospital Medical School, Cranmer Terr., London, SW17 ORE, United Kingdom.