1 Center for Outcomes Research and Evaluation, Yale New Haven Hospital, New Haven, Connecticut, USA.
2 Division of Cardiac Surgery, Yale School of Medicine, New Haven, Connecticut, USA.
3 Harvard Medical School, Boston, Massachusetts, USA.
4 Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
5 Section of Cardiovascular Medicine, Department of Internal Medicine, Yale School of Medicine and the Department of Health Policy and Management, Yale School of Public Health, New Haven, Connecticut, USA.