[1] King Edward Med Univ, Dept Cardiol, Lahore 54000, Pakistan
[2] King Edward Med Univ, Dept Med, Lahore, Pakistan
[3] Hamad Med Corp, POB 3050, Doha, Qatar
[4] Lincoln Med Ctr, Dept Med, Bronx, NY USA
[5] Beth Israel Lahey Hlth, Lahey Hosp & Med Ctr, Div Cardiovasc Med, Burlington, MA USA
[6] Duke Univ, Dept Med, Div Cardiol, Med Ctr, Durham, NC USA
[7] Duke Univ, Dept Med, Med Ctr, Durham, NC USA
[8] Duke Clin Res Inst, Durham, NC USA
[9] Univ Calif Los Angeles, Ahmanson UCLA Cardiomyopathy Ctr, Div Cardiol, Los Angeles, CA USA