[1] Univ Toronto, St Michaels Hosp, Div Cardiac Surg, Toronto, ON, Canada
[2] Univ Ottawa, Inst Heart, Ottawa, ON, Canada
[3] Univ British Columbia, Div Cardiovasc Surg, Vancouver, BC V5Z 1M9, Canada
[4] Dalhousie Univ, Div Cardiovasc Surg, Halifax, NS, Canada
[5] London Hlth Sci Ctr, Div Cardiac Surg, London, ON, Canada
[6] Univ Manitoba, Div Cardiac Surg, Winnipeg, MB, Canada
[7] McGill Univ, Div Cardiothorac Surg, Montreal, PQ, Canada
[8] Montreal Heart Inst, Dept Cardiac Surg, Montreal, PQ H1T 1C8, Canada
[9] Hamilton Hlth Sci Ctr, Div Cardiac Surg, Hamilton, ON, Canada
[10] Univ Calgary, Libin Cardiovasc Inst Alberta, Calgary, AB, Canada
[11] Northwestern Univ, NW Mem Hosp, Bluhm Cardiovasc Inst, Chicago, IL 60611 USA