1. Department of Cardiac Surgery, University of Michigan Medical School, Ann Arbor
2. School of Public Health, Department of Biostatistics, University of Michigan, Ann Arbor
3. University of Michigan Medical School, Ann Arbor
4. Department of Health Management and Policy, School of Public Health, University of Michigan
5. Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor
6. Department of Cardiothoracic Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania