1. Is Hospital Procedure Volume a Reliable Marker of Quality for Coronary Artery Bypass Surgery? A Comparison of Risk and Propensity Adjusted Operative and Midterm Outcomes 
Anoar Zacharias, MD, Thomas A. Schwann, MD, Christopher J. Riordan, MD, Samuel J. Durham, MD, Aamir Shah, MD, Thomas J. Papadimos, MD, Milo Engoren, MD, Robert H. Habib, PhD 
The Annals of Thoracic Surgery 
Volume 79, Issue 6, Pages (June 2005)
DOI: /j.athoracsur
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions

2. Fig 1
Receiver operator characteristic curve for predicting operative mortality for all patients as determined from logistic regression model (see Table 3) applied to all patients (thick line). Forcing hospital (low-volume hospital = 1; high-volume hospital = 0) variable into the model did not significantly alter the model prediction power (thin line).
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions

3. Fig 2
(Top) Comparison of cumulative unadjusted Kaplan-Meier survival for all low-volume hospital (LVH) patients versus all high-volume hospital (HVH) patients. (Bottom) Comparison of unadjusted Kaplan-Meier survival for low-volume versus high-volume hospital in risk-based sub-cohorts (low-risk, moderate-risk, and high-risk) based on the latest Society of Thoracic Surgeons (STS) risk model [19]. (See Results section for details.) (Error bars = standard error.) (CABG = coronary artery bypass grafting; RR = risk ratio.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions

4. Fig 3
Risk-adjusted 0 to 3-year survival for low-volume hospital (LVH) versus high-volume hospital (HVH) derived by Cox proportional hazard regression analysis with multiple other risk factor and demographic covariates (top) and non-parsimonious propensity model score as a single covariate of hospital volume (bottom). Model predictors are shown in Table 4. (CABG = coronary artery bypass grafting; RR = risk ratio.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions

5. Fig 4
Receiver operator characteristic curve of low-volume hospital (LVH) propensity score as a predictor of LVH actual patients (high-volume hospital [HVH] cohort: ± 0.138; LVH cohort: ± 0.274; p < ). The propensity score is based on a non-parsimonious logistic regression model utilizing the variables listed in Table 1. The area ± standard error under the receiver operator characteristic curve was ± (p < ) indicating good discrimination.
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions

6. Fig 5
Comparison of low-volume hospital (LVH) versus high-volume hospital (HVH) unadjusted operative mortality in propensity score quintile groups. Overall operative mortality comparisons were shown for reference.
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2005 The Society of Thoracic Surgeons Terms and Conditions