1. Northern New England Cardiovascular Disease Study Group; Department of Surgery, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756;
2. Northern New England Cardiovascular Disease Study Group; Department of Surgery, Cardiothoracic Surgery Section, Dartmouth-Hitchcock Medical Center, Lebanon, NH
3. Northern New England Cardiovascular Disease Study Group; Department of Community & Family Medicine, Dartmouth Medical School, Hanover