[1] MAYO CLIN, DEPT CARDIOL, JACKSONVILLE, FL USA
[2] OTTAWA CIVIC HOSP, DEPT MED, OTTAWA, ON, CANADA
[3] OTTAWA CIVIC HOSP, DEPT EPIDEMIOL, OTTAWA, ON, CANADA
[4] OTTAWA CIVIC HOSP, DEPT COMMUNITY MED, OTTAWA, ON, CANADA
[5] UNIV WASHINGTON, DEPT BIOSTAT, SEATTLE, WA USA
[6] UNIV TEXAS, HLTH SCI CTR, DEPT MED NEUROL, SAN ANTONIO, TX USA