1. Cardiovascular Research Laboratory (E.O., J.M.G.), Department of Exercise Sciences, University of Toronto, Toronto, Ontario, M5S 2W6 Canada
2. Division of Cardiology (J.M.G., S.M.), Mt Sinai Hospital, Toronto, Ontario, M5G 1X5 Canada
3. Division of Cardiology (P.J.H.), Women's College Hospital, Department of Medicine, University of Toronto, Ontario, M5S 1B2 Canada