1. From the Divisions of Cardiac Surgery (M.B., B.K.L., T.G.M., M.R., F.D.R.) and Cardiac Anesthesia (H.J.N.), University of Ottawa Heart Institute, and the Department of Nuclear Medicine, The Ottawa Hospital (W.Z.), Ottawa, Ontario, Canada, and Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass (F.W.S.).