1. Division of Cardiology, Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY (S.M.K., E.C., A.N., L.S.R., A.G., A.B.B., H.G., E.Y.W.).
2. Heart, Vascular, and Thoracic Institute and Lerner Research Institute, Cleveland Clinic, OH (M.K.C.).
3. The Kansas City Heart Rhythm Institute & Research Foundation, Overland Park, KS (R.G.).