1. From the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN (S.A.L.); and the Departments of Radiology (R.C.), Medicine (A.C.S.S., J.W.C.), and Pathology (D.S.P.), Massachusetts General Hospital, and the Departments of Radiology (R.C.), Medicine (A.C.S.S., J.W.C.), and Pathology (D.S.P.), Harvard Medical School — both in Boston.