1. Effects of institutional volumes on operative outcomes for aortic root replacement in North America 
G. Chad Hughes, MD, Yue Zhao, PhD, J. Scott Rankin, MD, John E. Scarborough, MD, Sean O’Brien, PhD, Joseph E. Bavaria, MD, Walter G. Wolfe, MD, Jeffrey G. Gaca, MD, James S. Gammie, MD, David M. Shahian, MD, Peter K. Smith, MD 
The Journal of Thoracic and Cardiovascular Surgery 
Volume 145, Issue 1, Pages (January 2013)
DOI: /j.jtcvs
Copyright © 2013 The American Association for Thoracic Surgery Terms and Conditions

2. Figure 1
A, Observed relationship between annual institutional case volume and risk-adjusted odds ratio for operative mortality ±2 standard deviation as assessed with regression analysis. Mortality increased as institutional case volume declined. B, Same relationship as in Figure A, except curve fitting was with spline function with 3 knots. Variation in location of knots had little effect on the relationship.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /j.jtcvs )
Copyright © 2013 The American Association for Thoracic Surgery Terms and Conditions