1. Division of Cardiac Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
2. Division of Cardiac Surgery, Penn State University Hershey Medical Center, Hershey, PA, USA
3. Maryland Cardiac Surgery Quality Initiative, Baltimore, MD, USA
4. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, MD, USA
5. Division of Cardiac Surgery, University of Maryland Saint Joseph Medical Center, Baltimore, MD, USA