1. From the Division of Cardiovascular Diseases and Internal Medicine (L.H.L., J.K.O., J.B.S., A.J.T.), the Division of Thoracic and Cardiovascular Surgery (H.V.S., G.K.D.), and the Section of Biostatistics (D.W.M.), Mayo Clinic and Mayo Foundation, Rochester, Minn. Dr Ling is now at the Cardiac Department, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074.