[1] John Radcliffe Hosp, Dept Cardiovasc Med, Oxford OX3 9DU, England
[2] Hamilton Gen Hosp, McMaster Clin, Populat Hlth Inst, Hamilton, ON, Canada
[3] McMaster Univ, HGH McMaster Clin, Hamilton Gen Hosp, Canadian Collaborat, Hamilton, ON, Canada
[4] Univ Alberta, Epidemiol Coordinating & Res Ctr, Edmonton, AB, Canada
[5] Inst Cardiovasc Rosario, Rosario, Santa Fe, Argentina
[6] Fred Hutchinson Canc Res Ctr, Clin Trial Serv Unit, Seattle, WA 98104 USA