[1] Johns Hopkins Univ Hosp, Div Cardiol, Baltimore, MD 21287 USA
[2] Univ Calif San Francisco, Sch Med, Gen Internal Med Sect, Vet Affairs Med Ctr, San Francisco, CA 94121 USA
[3] Univ Calif San Francisco, Sch Med, Dept Med, San Francisco, CA 94121 USA
[4] Univ Calif San Francisco, Sch Med, Dept Epidemiol, San Francisco, CA 94121 USA
[5] Univ Calif San Francisco, Sch Med, Dept Biostat, San Francisco, CA 94121 USA
[6] Univ Calif San Francisco, Sch Med, Div Cardiol, San Francisco, CA 94121 USA