[1] Massachusetts Gen Hosp, Dept Med, Cardiol Div, Boston, MA 02114 USA
[2] Northwestern Univ, Dept Med, Feinberg Sch Med, Div Cardiol, Chicago, IL 60611 USA
[3] Univ Texas Southwestern Med Ctr, Dept Internal Med, Div Cardiol, Dallas, TX USA
[4] Parkland Hlth & Hosp Syst, Dallas, TX USA
[5] Univ Calif Los Angeles, Ahmanson UCLA Cardiomyopathy Ctr, Los Angeles, CA USA
[6] Univ Mississippi, Med Ctr, Dept Med, Jackson, MS 39216 USA
[7] Harvard Med Sch, Brigham & Womens Hosp, Heart & Vasc Ctr, 75 Francis St, Boston, MA 02115 USA