1. Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor (N.R.S., M.S., D.S., H.S.G.).
2. Division of Cardiology, Spectrum Health, Grand Rapids, MI (R.D.M.).
3. Department of Medicine, Section of Cardiology, Veterans Affairs Medical Center, Ann Arbor, MI (D.S., H.S.G.).
4. Department of Cardiovascular Medicine, Beaumont Hospital, Royal Oak, MI (S.R.D.).
5. Cardiac and Vascular Research Center of Northern Michigan, Petoskey (L.A.C.).