1. Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, California
2. Division of Cardiovascular Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, California
3. Medical Service, Section of Cardiology, Palo Alto Veterans Affairs Health Care System, Palo Alto, California
4. Division of General Surgery, Palo Alto Veterans Affairs Health Care System, Palo Alto, California
5. Department of Surgery, Stanford University School of Medicine, Stanford, California