1. From Libin Cardiovascular Institute of Alberta (P.W.M.F.), Division of Cardiac Surgery, Department of Cardiac Sciences, University of Calgary, Calgary, Alberta, Canada; and Bluhm Cardiovascular Institute, Division of Cardiothoracic Surgery (P.M.M.) and Division of Cardiology (R.O.B.), Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, Ill.