[1] Brigham & Womens Hosp, Dept Med, Cardiovasc Div, 75 Francis St, Boston, MA 02115 USA
[2] Univ Groningen, Univ Med Ctr Groningen, Dept Cardiol, Groningen, Netherlands
[3] Univ Utah, Div Cardiovasc Med, Sch Med, Salt Lake City, UT USA
[4] Montreal Heart Inst, Dept Med, Montreal, PQ, Canada
[5] Univ Michigan, Sch Med, Dept Internal Med, Ann Arbor, MI USA
[6] Northwestern Univ, Dept Med, Div Cardiol, Feinberg Sch Med, Chicago, IL 60611 USA