[1] Univ N Carolina, Dept Cardiothorac Surg, Chapel Hill, NC USA
[2] Yale Univ, Yale Sch Med, Sect Cardiovasc Med, New Haven, CT USA
[3] Kaiser Permanente San Francisco Med Ctr, Dept Cardiol, San Francisco, CA USA
[4] Kaiser Permanente Northern Calif, Div Res, Oakland, CA USA
[5] Univ North Carolina Syst, 4005 Burnett Womack,CB 7050, Chapel Hill, NC 27599 USA