[1] Duke Clin Rsch Inst, Durham, NC USA
[2] Univ Alberta, Dept Med, Div Cardiol, Edmonton, AB, Canada
[3] Thomas Jefferson Univ, Dept Med, Div Cardiol, Philadelphia, PA 19107 USA
[4] Univ Alberta, CVC Rsch Grp, Edmonton, AB, Canada
[5] San Francisco VA Hosp, San Francisco, CA USA
[6] Univ Calgary, Dept Cardiac Sci, Calgary, AB, Canada
[7] Cleveland Clin, Cleveland, OH 44106 USA
[8] Duke Univ, Med Ctr, Durham, NC USA