[1] Lahey Clin Fdn, Dept Cardiovasc Med, Burlington, MA 01805 USA
[2] Univ Massachusetts, Sch Med, Worcester, MA 01655 USA
[3] Ralph H Johnson Dept Vet Affairs Med Ctr, Charleston, SC 29401 USA
[4] Med Univ S Carolina, Gazes Cardiac Res Inst, Dept Med, Div Cardiol, Charleston, SC 29425 USA