[1] Duke Univ, Clin Res Inst, Dept Cardiol, Durham, NC 27705 USA
[2] Guilford Cty Emergency Med Serv, Greensboro, NC USA
[3] Copenhagen Univ Hosp, Ctr Heart, Dept Med B, Rigshosp, Copenhagen, Denmark
[4] Moses Cone Mem Hosp, LeBauer Cardiovasc Res Fdn, Greensboro, NC USA
[5] Univ Washington, Dept Hlth Serv, Seattle, WA 98195 USA