1. Peter Munk Cardiac Centre and Heart and Stroke Richard Lewar Centre, Toronto, Canada (L.C.G., M.E.F.).
2. University of Toronto, Canada (L.C.G., V.R., M.E.F.).
3. Instituto do Coracao (InCor), Faculdade de Medicina da Universidade de Sao Paulo, Brazil (L.C.G.).
4. Peter Munk Cardiac Centre and Toronto General Research Institute, Division of Cardiovascular Surgery, Toronto General Hospital (V.R.)