1. From the Cardiac Arrhythmia Center, Cardiovascular Division, Department of Medicine, University of Minnesota Medical School, Minneapolis (I.C., K.K.); Division of Cardiology (Y.C., J.-M.L., V.N.T.) and Department of Pathology (R.D.), Veterans Affairs Medical Center, and University of Minnesota (Y.C., J.-M.L., V.N.T.), Minneapolis, Minn.