1. Division of Cardiology, Duke University, Durham, North Carolina (C.S.D., M.D.K., G.S.Y., A.Y.S., A.W., S.V., A.M.K.).
2. Medstar Health Research Institute, Washington, D.C. (A.S.).
3. Duke Cardiovascular MR Center, Durham, NC (A.S.).
4. Department of Surgery, Duke University, Durham, North Carolina (D.D.G.).