[1] Munroe Reg Med Ctr, Ocala Heart Inst, Ocala, FL USA
[2] Harvard Univ, Sch Med, Dept Hlth Care Policy, Boston, MA 02115 USA
[3] Boston Med Ctr, Cardiol Sect, Dept Med, Boston, MA USA
[4] Northwestern Univ, Dept Med, Div Cardiol, Feinberg Sch Med, Chicago, IL 60611 USA
[5] Harvard Univ, Sch Publ Hlth, Dept Biostat, Boston, MA 02115 USA