1. Department of Cardiac Surgery, University of Michigan Medical School, Ann Arbor (M.P.T., X.W., R.L.P., D.S.L.).
2. Michigan Society of Thoracic and Cardiovascular Surgeons-Quality Collaborative, Ann Arbor (L.C., R.L.P., D.S.L.)
3. University of Michigan Medical School, Ann Arbor (R.J.S.).
4. Henry Ford Macomb Hospital, Clinton Township, MI (S.D.H.).
5. Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor (M.Z.).