1. From the Division of Circulatory Physiology, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY (U.P.J., T.V., P.C.C.); the Section of Cardiovascular Medicine, Department of Medicine, Yale University School of Medicine, New Haven, Conn (S.D.K.); and the Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, NY (F.L., T.H.L.J.).