[1] Northwestern Univ, Feinberg Sch Med, Div Cardiol, Chicago, IL 60611 USA
[2] Brigham & Womens Hosp, Heart & Vasc Ctr, Div Cardiol, 75 Francis St, Boston, MA 02115 USA
[3] Duke Clin Rsch Inst, Durham, NC USA
[4] Duke Univ, Med Ctr, Duke Clin Rsch Inst, Durham, NC USA
[5] Duke Univ, Med Ctr, Div Cardiol, Durham, NC USA
[6] Mayo Clin, Dept Cardiovasc Dis, Rochester, MN USA
[7] Univ Mississippi, Sch Med, Dept Med, Jackson, MS 39216 USA