[1] Univ Calif San Francisco, Dept Med, Div Cardiol, San Francisco, CA 94143 USA
[2] Stanford Univ, Dept Med, Div Cardiovasc Med, Stanford, CA 94305 USA
[3] Duke Univ, Med Ctr, Duke Clin Res Inst, Durham, NC USA
[4] Emory Univ, Div Cardiol, Dept Med, Atlanta, GA 30322 USA