[1] Med Coll Wisconsin, Dept Emergency Med, Milwaukee, WI 53226 USA
[2] Med Coll Wisconsin, Div Biostat, Milwaukee, WI 53226 USA
[3] Adv Circulatory Syst Inc, Eden Prairie, MN 55344 USA
[4] Univ Minnesota, Cardiac Arrhythmia Ctr, Minneapolis, MN 55455 USA
[5] Minneapolis Med Res Fdn Inc, Minneapolis, MN 55404 USA