[1] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[2] Duke Clin Res Inst, Durham, NC USA
[3] Northwestern Univ, Div Cardiol, Feinberg Sch Med, Chicago, IL 60611 USA
[4] Stanford Univ, Sch Med, Div Cardiol, Palo Alto, CA 94304 USA
[5] Harvard Med Sch, Brigham & Womens Hosp, Inst Heart & Vasc, Boston, MA 02115 USA
[6] Univ Calif Los Angeles, Ahmanson UCLA Cardiomyopathy Ctr, Div Cardiol, Los Angeles, CA 90095 USA