1 Cardiac Electrophysiology Section, Division of Cardiology, Department of Medicine, University of California, San Diego.
2 Department of Veteran Affairs Eastern Colorado Health Care System, Denver 3Division of Cardiology, Colorado Cardiovascular Outcomes Research Consortium, University of Colorado School of Medicine, Denver.
3 Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, University of California, San Francisco.