1. Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis Davis, CA
2. Department of Veterans Affairs, Northern California Health Care System, Mather, CA
3. Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, IA
4. Department of Veterans Affairs, Iowa City Medical Center, Iowa City, IA