1. From the Division of Cardiovascular Medicine (R.D.B., R.L.B., M.R., N.S.C., K.A.E.), Department of Internal Medicine, the Division of Thoracic Radiology (S.P., E.A.K.), Department of Radiology, and the Division of Vascular Surgery (T.W.W., P.K.H.), Department of Surgery, University of Michigan, Ann Arbor.