1. From the Cardiovascular Research Center (S.K., S.A.L.), Massachusetts General Hospital, Boston
2. Cardiology Division (S.K.), Massachusetts General Hospital, Boston
3. Broad Institute of Harvard University, Massachusetts Institute of Technology, Cambridge (S.K., S.A.L.)
4. Population Health Research Institute, McMaster University, Hamilton, ON, CA (J.S.H., W.F.M.).
5. Cardiac Arrhythmia Service (S.A.L.), Massachusetts General Hospital, Boston