1. From the Division of Cardiovascular Diseases and Internal Medicine (D.G.H., R.A.N., S.T.H., D.R.H., A.J.T.) and the Section of Cardiovascular Surgery (G.K.D.), Mayo Clinic and Mayo Foundation, Rochester, Minn, and the Division of Cardiovascular Diseases (C.P.A.), Mayo Clinic, Scottsdale, Ariz.