[1] Duke Univ, Sch Med, Dept Med, Durham, NC 27706 USA
[2] Duke Univ, Sch Med, Duke Clin Res Inst, Durham, NC USA
[3] Northwestern Univ, Feinberg Sch Med, Div Cardiol, Chicago, IL 60611 USA
[4] Harvard Univ, Brigham & Womens Hosp, Sch Med, Dept Med,Heart & Vasc Ctr, Boston, MA 02115 USA
[5] Vet Affairs Palo Alto Hlth Care Syst, Dept Med, Palo Alto, CA USA
[6] Stanford Univ, Stanford, CA 94305 USA
[7] Univ Calif Los Angeles, Ahmanson UCLA Cardiomyopathy Ctr, Los Angeles, CA USA