[1] Brigham & Womens Hosp, Dept Med, 75 Francis St, Boston, MA 02115 USA
[2] Brown Univ, Warren Alpert Med Sch, Div Cardiol, Providence, RI 02912 USA
[3] Harvard Med Sch, Dept Med, Massachusetts Gen Hosp, Boston, MA USA
[4] Harvard Med Sch, Brigham & Womens Hosp, Heart & Vasc Ctr, Boston, MA USA
[5] Ronald Reagan UCLA Med Ctr, Ahmanson UCLA Cardiomyopathy Ctr, Los Angeles, CA 90095 USA