1. Health Services Research Training Program, University of Alabama at Birmingham, Birmingham, Alabama.
2. Division of Cardiovascular Diseases, University of Alabama at Birmingham, Birmingham, Alabama.
3. Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
4. Division of Cardiology, University of California, San Francisco, San Francisco, California.
5. MedStar Research Institute, Hyattsville, Maryland.
6. Department of Medicine, Montreal Heart Institute, Montreal, Canada.