1. Division of General Internal Medicine, Department of Medicine (P.W.G.), Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
2. Cardiovascular Outcomes, Quality, and Evaluation Research Center, University of Pennsylvania School of Medicine, Philadelphia, PA (P.W.G., N.D.D.).
3. Leonard Davis Institute of Health Economics, Philadelphia, PA (P.W.G., N.D.D.).
4. Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA (P.W.G.).
5. Division of Cardiovascular Surgery, Department of Surgery (N.D.D.), Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.