[1] Harvard Univ, Brigham & Womens Hosp, Sch Med, Dept Med,Div Pharmacoepidemiol & Pharmacoecon, Boston, MA 02115 USA
[2] Boca Raton Community Hosp, Lynn Heart Inst, Div Cardiothorac Surg, Boca Raton, FL USA
[3] Harvard Univ, Sch Med, Massachusetts Gen Hosp, Cardiac Arrhythmia Serv, Boston, MA 02115 USA