Society Of Thoracic Surgeons Risk Model Research Articles

Abstract 18614: Comparison of the New EuroSCORE II with the Original EuroSCORE and the Society of Thoracic Surgeons Risk Score

Background: The new EuroSCORE II was developed to improve the prediction risk model of the EuroSCORE I.. In the USA, the Society of Thoracic Surgeons (STS) risk score is more accepted despite being less user friendly and non-applicable to some of the cardiac surgeries. The purpose of this study was to compare the performance of the new EuroSCORE II with the logistic EuroSCORE I and STS mortality predicted risk score . Methods: Prospectively collected data from all cardiac surgery patients at a single center with complete data for the three scores (N=9,966) was used. A subabnalysis for patients with cardiac surgeries not accommodated by the STS risk model was performed for comparison of the EuroSCORE II & I (N=4,738). Correlations were conducted between each score and ROC curves were calculated for operative mortality determining the discriminative ability score. Results: Our center’s observed operative mortality was 2% -the mean predicted mortality for STS was 2.8%, 3.3% for EuroSCORE II and 7.7% for EuroSCORE I. The discriminative ability of the EuroSCORE II for operative mortality by the area under the curve (AUC) was 0.836, for EuroSCORE I (AUC=0.812) and for the STS score (AUC=0.833). The EuroSCORE II was highly correlated with the EuroSCORE I ( r =0.83, p <0.001) and the STS score ( r =0.78, p <0.001). The EuroSCORE II had a higher correlation with the STS score than the EuroSCORE I ( r =0.70, p <0.001). In the subanalyses comparing the EuroSCORE II vs I, the scores were highly correlated ( r =0.74, p <0.001). For operative mortality (observed=4%), the EuroSCORE II had better discriminative ability (expected=5.6%, AUC=0.749) compared to EuroSCORE I (expected=12.4%, AUC=0.687). Conclusions: The new EuroScore II has better operative mortality discrimination compared to the original EuroSCORE, which greatly overestimated the predicted risk of operative mortality. The EuroSCORE II fared well with the STS risk score. Due to the inclusive nature of the EuroSCORE II for multiple procedures, it provides more flexibility than the STS score when dealing with patients undergoing very complex procedures. The EuroSCORE II should be considered when obtaining a risk score for complex cardiac surgical patients.

Does the Society of Thoracic Surgeons risk score accurately predict operative mortality for patients with pulmonary hypertension?

This study assessed the impact of pulmonary hypertension (PH) on morbidity and mortality after the most common cardiac operations and evaluated the accuracy of the Society of Thoracic Surgeons (STS) risk model for patients with PH. At a single center between 1994 and 2010, all adult cardiac operations performed with recorded preoperative mean pulmonary arterial pressure (MPAP) and STS predicted mortality were reviewed. MPAP was defined as normal (<25 mm Hg) or as mild (25-34 mm Hg), moderate (35-44 mm Hg), or severe (≥ 45 mm Hg) PH. Multivariate analysis was performed to elucidate the contribution of PH to morbidity and mortality. In all, 3343 patient records were reviewed. Coronary artery bypass grafting (CABG) was the most common procedure (67.5%), followed by aortic valve replacement (24.9%) and mitral valve procedures (6.3%). Postoperative complications and mortality increased with increasing MPAP. Multivariable analysis found that both moderate (odds ratio, 7.17; P < .001) and severe (odds ratio, 13.73; P < .001) PH were significantly associated with increased mortality, even after accounting for STS risk. A subset analysis of isolated CABG cases revealed markedly increased mortality for all categories of PH (mild odds ratio, 1.99; moderate odds ratio, 11.5; severe odds ratio, 38.9; P < .001). Morbidity and mortality were independently associated with PH. Observed mortality was significantly higher than predicted by the STS model for patients with moderate and severe PH, particularly in isolated CABG. Addition of PH to the STS risk model should be considered, or alternative tools should be used to assess risk in these patients.

Major risk stratification models do not predict perioperative outcome after coronary artery bypass grafting in patients with previous percutaneous intervention

To investigate whether common risk stratification models in cardiac surgery predict perioperative outcome of coronary artery bypass grafting (CABG) in patients with previous percutaneous coronary interventions (PCIs). We retrospectively analyzed the perioperative mortality and morbidity of 367 patients with prior elective PCI versus 2361 patients without prior PCI, who underwent first-time isolated CABG between 2001 and 2009 at our institution. Receiver operating characteristics (ROC) were used to describe the performance and accuracy of the European System for Cardiac Operative Risk Evaluation (EuroSCORE) and the Society of Thoracic Surgeons (STS) risk model in predicting mortality and morbidity. Both groups were comparable concerning preoperative logistic EuroSCORE (PCI: 4.9 ± 6.57, non-PCI: 4.60 ± 5.45, p=0.51). Patients with previous elective PCI had increased perioperative mortality (PCI: 3.8% vs non-PCI: 2.1%, p=0.01) and higher rates of major adverse cardiac events (8.4% vs 4.5% respectively, p=0.003). Discriminatory power for 30-day mortality was higher in the non-PCI group (EuroSCORE area under the curve (AUC): 0.875 vs 0.552 in the PCI group). Logistic EuroSCORE predicted 30-day mortality in the non-PCI group (confidence interval (CI)=0.806-0.934, p=0.0004) but not in the PCI group (CI=0.301-0.765, p=0.8). Discriminatory power for morbidity or mortality (M&M) was lower in the PCI group (AUC: 0.980 vs 0.713 for the non-PCI group). The STS risk model had a lower discriminatory power for predicting M&M in PCI patients (AUC: 0.611 vs 0.686 for the non-PCI group, p<0.001). The EuroSCORE and the STS risk model were inaccurate in predicting perioperative mortality after CABG in patients with history of elective PCI. There is a need for modification of risk models to improve risk assessment for surgical candidates with prior PCI.

The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Part 3—Valve Plus Coronary Artery Bypass Grafting Surgery

Since 1999, The Society of Thoracic Surgeons (STS) has published two risk models that can be used to adjust the results of valve surgery combined with coronary artery bypass graft surgery (CABG). The most recent was developed from data for patients who had surgery between 1994 and 1997 using operative mortality as the only endpoint. Furthermore, this model did not specifically consider mitral valve repair plus CABG, an increasingly common procedure. Consistent with STS policy of periodically updating and improving its risk models, new models for valve surgery combined with CABG have been developed. These models specifically address both perioperative morbidity and mitral valve repair, and they are based on contemporary data. The final study population consisted of 101,661 procedures, including aortic valve replacement (AVR) plus CABG, mitral valve replacement (MVR) plus CABG, or mitral valve repair (MVRepair) plus CABG between January 1, 2002, and December 31, 2006. Model outcomes included operative mortality, stroke, deep sternal wound infection, reoperation, prolonged ventilation, renal failure, composite major morbidity or mortality, prolonged postoperative length of stay, and short postoperative length of stay. Candidate variables were screened for frequency of missing data, and imputation techniques were used where appropriate. Stepwise variable selection was employed, supplemented by advice from an expert panel of cardiac surgeons and biostatisticians. Several variables were forced into models to insure face validity (eg, atrial fibrillation for the permanent stroke model, sex for all models). Based on preliminary analyses of the data, a single model was employed for valve plus CABG, with indicator variables for the specific type of procedure. Interaction terms were included to allow for differential impact of predictor variables depending on procedure type. After validating the model in the 40% validation sample, the development and validation samples were then combined, and the final model coefficients were estimated using the overall 100% combined sample. The final logistic regression model was estimated using generalized estimating equations to account for clustering of patients within institutions. The c-index for mortality prediction for the overall valve plus CABG population was 0.75. Morbidity model c-indices for specific complications (permanent stroke, renal failure, prolonged ventilation > 24 hours, deep sternal wound infection, reoperation for any reason, major morbidity or mortality composite, and prolonged postoperative length of stay) for the overall group of valve plus CABG procedures ranged from 0.622 to 0.724, and calibration was excellent. New STS risk models have been developed for heart valve surgery combined with CABG. These are the first valve plus CABG models that also include risk prediction for individual major morbidities, composite major morbidity or mortality, and short and prolonged length of stay.

The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Introduction

The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Part 1—Coronary Artery Bypass Grafting SurgeryThe Annals of Thoracic SurgeryVol. 88Issue 1PreviewThe first version of The Society of Thoracic Surgeons National Adult Cardiac Surgery Database (STS NCD) was developed nearly 2 decades ago. Since its inception, the number of participants has grown dramatically, patient acuity has increased, and overall outcomes have consistently improved. To adjust for these and other changes, all STS risk models have undergone periodic revisions. This report provides a detailed description of the 2008 STS risk model for coronary artery bypass grafting surgery (CABG). Full-Text PDF The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Part 2—Isolated Valve SurgeryThe Annals of Thoracic SurgeryVol. 88Issue 1PreviewAdjustment for case-mix is essential when using observational data to compare surgical techniques or providers. That is most often accomplished through the use of risk models that account for preoperative patient factors that may impact outcomes. The Society of Thoracic Surgeons (STS) uses such risk models to create risk-adjusted performance reports for participants in the STS National Adult Cardiac Surgery Database (NCD). Although risk models were initially developed for coronary artery bypass surgery, similar models have now been developed for use with heart valve surgery, particularly as the proportion of such procedures has increased. Full-Text PDF The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Part 3—Valve Plus Coronary Artery Bypass Grafting SurgeryThe Annals of Thoracic SurgeryVol. 88Issue 1PreviewSince 1999, The Society of Thoracic Surgeons (STS) has published two risk models that can be used to adjust the results of valve surgery combined with coronary artery bypass graft surgery (CABG). The most recent was developed from data for patients who had surgery between 1994 and 1997 using operative mortality as the only endpoint. Furthermore, this model did not specifically consider mitral valve repair plus CABG, an increasingly common procedure. Consistent with STS policy of periodically updating and improving its risk models, new models for valve surgery combined with CABG have been developed. Full-Text PDF

The Society of Thoracic Surgeons 2008 Cardiac Surgery Risk Models: Part 2—Isolated Valve Surgery

Adjustment for case-mix is essential when using observational data to compare surgical techniques or providers. That is most often accomplished through the use of risk models that account for preoperative patient factors that may impact outcomes. The Society of Thoracic Surgeons (STS) uses such risk models to create risk-adjusted performance reports for participants in the STS National Adult Cardiac Surgery Database (NCD). Although risk models were initially developed for coronary artery bypass surgery, similar models have now been developed for use with heart valve surgery, particularly as the proportion of such procedures has increased. The last published STS model for isolated valve surgery was based on data from 1994 to 1997 and did not include patients undergoing mitral valve repair. STS has developed new valve surgery models using contemporary data that include both valve repair as well as replacement. Expanding upon existing valve models, the new STS models include several nonfatal complications in addition to mortality. Using STS data from 2002 to 2006, isolated valve surgery risk models were developed for operative mortality, permanent stroke, renal failure, prolonged ventilation (> 24 hours), deep sternal wound infection, reoperation for any reason, a major morbidity or mortality composite endpoint, prolonged postoperative length of stay, and short postoperative length of stay. The study population consisted of adult patients who underwent one of three types of valve surgery: isolated aortic valve replacement (n = 67,292), isolated mitral valve replacement (n = 21,229), or isolated mitral valve repair (n = 21,238). The population was divided into a 60% development sample and a 40% validation sample. After an initial empirical investigation, the three surgery groups were combined into a single logistic regression model with numerous interactions to allow the covariate effects to differ across these groups. Variables were selected based on a combination of automated stepwise selection and expert panel review. Unadjusted operative mortality (in-hospital regardless of timing, and 30-day regardless of venue) for all isolated valve procedures was 3.4%, and unadjusted in-hospital morbidity rates ranged from 0.3% for deep sternal wound infection to 11.8% for prolonged ventilation. The number of predictors in each model ranged from 10 covariates in the sternal infection model to 24 covariates in the composite mortality plus morbidity model. Discrimination as measured by the c-index ranged from 0.639 for reoperation to 0.799 for mortality. When patients in the validation sample were grouped into 10 categories based on deciles of predicted risk, the average absolute difference between observed versus predicted events within these groups ranged from 0.06% for deep sternal wound infection to 1.06% for prolonged postoperative stay. The new STS risk models for valve surgery include mitral valve repair as well as multiple endpoints other than mortality. Model coefficients are provided and an online risk calculator is publicly available from The Society of Thoracic Surgeons website.

Early efficacy of CABG care delivery in a low procedure-volume community hospital: operative and midterm results

BackgroundThe Leapfrog Group recommended that coronary artery bypass grafting (CABG) surgery should be done at high volume hospitals (>450 per year) without corresponding surgeon-volume criteria. The latter confounds procedure-volume effects substantially, and it is suggested that high surgeon-volume (>125 per year) rather than hospital-volume may be a more appropriate indicator of CABG quality.MethodsWe assessed 3-year isolated CABG morbidity and mortality outcomes at a low-volume hospital (LVH: 504 cases) and compared them to the corresponding Society of Thoracic Surgeons (STS) national data over the same period (2001–2003). All CABGs were performed by 5 high-volume surgeons (161–285 per year). "Best practice" care at LVH – including effective practice guidelines, protocols, data acquisition capabilities, case review process, dedicated facilities and support personnel – were closely modeled after a high-volume hospital served by the same surgeon-team.ResultsOperative mortality was similar for LVH and STS (OM: 2.38% vs. 2.53%), and the corresponding LVH observed-to-expected mortality (O/E = 0.81) indicated good quality relative to the STS risk model (O/E<1). Also, these results were consistent irrespective of risk category: O/E was 0, 0.9 and 1.03 for very-low risk (<1%), low risk (1–3%) and moderate-to-high risk category (>3%), respectively. Postoperative leg wound infections, ventilator hours, renal dysfunction (no dialysis), and atrial fibrillation were higher for LVH, but hospital stay was not. The unadjusted Kaplan-Meier survival for the LVH cohort was 96%, 94%, and 92% at one, two, and three years, respectively.ConclusionOur results demonstrated that high quality CABG care can be achieved at LVH programs if 1) served by high volume surgeons and 2) patient care procedures similar to those of large programs are implemented. This approach may prove a useful paradigm to ensure high quality CABG care and early efficacy at low volume institutions that wish to comply with the Leapfrog standards.

The early efficacy of CABG care delivery in a low procedure-volume community hospital: operative and midterm results

The Leapfrog Group recommended that CABG surgery should be done at high volume hospitals (> 450 per year) without corresponding surgeon-volume criteria. Recent studies have indicated that the effects of hospital volume are substantially confounded by surgeon volume, and that high surgeon volume (>125 per year) may be a more appropriate indicator of CABG quality. We thus compared operative morbidity and mortality outcomes for a low-volume hospital (LVH) (504 CABG, 2001–2003) served by five high-volume surgeons (161–285 per year) with the corresponding Society of Thoracic Surgeons (STS) national data over the same period. The LVH program implemented 'best practice' care including effective practice guidelines, protocols, data acquisition capabilities, case review process, dedicated facilities and support personnel (anesthesiology, intensivists and pharmacists). Operative mortality was similar for LVH and STS (OM: 2.38% vs 2.53%), and the corresponding LVH observed-to-expected mortality (O/E = 0.81) indicated good quality relative to the STS risk model (O/E 3%) categories, respectively. While postoperative leg wound infections, ventilator hours, renal failure, and atrial fibrillation were increased in the LVH, the length of stay was not. The unadjusted Kaplan–Meier survival for the LVH cohort was 96%, 94%, and 92% at 1, 2, and 3 years, respectively. Our results demonstrated that high-quality CABG care can be achieved at LVH programs when served by high-volume cardiac surgeons. This approach may prove a useful paradigm to ensure high-quality CABG care and early efficacy at low-volume institutions (Table ​(Table11 shows predictors of 0-year to 3-year mortality; Cox regression). Table 1

1995 Coronary Artery Bypass Risk Model: The Society of Thoracic Surgeons Adult Cardiac National Database

Background. The Society of Thoracic Surgeons (STS) Adult Cardiac National Database has recently completed the development of the 1995 risk model to be used to estimate the risk of operative death for isolated coronary artery bypass graft (CABG) procedures. This article describes the detailed methodology used, as well as a new Expert Advisory Panel review mechanism that was initiated by The Society.Methods. Placing emphasis on clinical relevance, data quality, data completeness, and univariate analyses, a logistic regression analysis was used to develop the 1995 CABG-only risk model. The STS National Office invited an Expert Advisory Panel (composed of nationally recognized, independent biostatisticians) to review the modeling process used.Results. The 1995 CABG-only model details are reported. Standard performance measures indicated the model had high predictive power and an acceptable level of calibration. The Expert Advisory Panel reviewed the 1995 CABG model and concluded that the current modeling techniques were adequate. Suggestions for future model development and reporting were proposed by the Panel.Conclusions. The most current STS risk model of CABG operative mortality is a reliable and statistically valid tool. Its development and performance have been critically examined and approved by an independent panel of experts.