Society Of Thoracic Surgeons Risk Calculator Research Articles

Intraoperative Features Improve Model Risk Predictions After Coronary Artery Bypass Grafting

BackgroundIntraoperative physiologic parameters could offer predictive utility in evaluating risk of adverse postoperative events yet are not included in current standard risk models. This study examined whether the inclusion of continuous intraoperative data improved machine learning model predictions for multiple outcomes after coronary artery bypass grafting, including 30-day mortality, renal failure, reoperation, prolonged ventilation, and combined morbidity and mortality (MM). MethodsThe Society of Thoracic Surgeons (STS) database features and risk scores were combined with retrospectively gathered continuous intraoperative data from patients. Risk models were developed for each outcome by training a logistic regression classifier on intraoperative data using 5-fold cross-validation. STS risk scores were included as offset terms in the models. ResultsCompared with the STS Risk Calculator, models developed using a combination of the intraoperative features and the STS preoperative risk score had improved mean area under the receiver operating characteristic curve for prolonged ventilation (0.750 [95% CI, 0.690-0.809] vs 0.800 [95% CI, 0.750-0.851]) and MM (0.695 [95% CI, 0.644-0.746] vs 0.724 [95% CI, 0.673-0.775]). Additionally, models developed using intraoperative features had improved calibration, measured with Brier score, for prolonged ventilation (0.060 [95% CI, 0.050-0.070] vs 0.055 [95% CI, 0.045-0.065]) and MM (0.092 [95% CI, 0.081-0.103] vs 0.087 [95% CI, 0.075-0.098]). ConclusionsThe inclusion of time series intraoperative data in risk models may improve early postoperative care by identifying patients who require closer monitoring postoperatively.

Burden of Tricuspid Regurgitation in Patients Undergoing Coronary Artery Bypass Grafting

Tricuspid regurgitation (TR) is associated with poor outcomes after cardiac surgery. Guidelines recommend correction of severe TR in patients undergoing left-sided valve surgery but not coronary artery bypass graft surgery (CABG). We sought to evaluate impact of TR on outcomes after CABG. All patients (n= 28,027) undergoing CABG in The Society of Thoracic Surgeons (STS) regional database (2011 to 2018) were stratified by TR severity. Primary outcomes included major morbidity or mortality, which were compared using univariate analysis. Of patients undergoing CABG, 4837 (17%) had mild, 800 (3%) had moderate, and 81 (0.29%) had severe TR. Increased severity was associated with higher rate of preoperative heart failure (none 5162 [23.4%] vs mild 1697 [35%] vs moderate 427 [53%] vs severe 54 [67%], P < .001] and STS predicted risk of mortality (1.0 [0.6 to 1.9) vs 1.4 [0.8 to 2.9] vs 2.8 [1.4 to 5.4] vs 6.2 [2.2 to 11.4], P < .001). Increasing severity was associated with higher postoperative rate of renal failure (426 [1.9%] vs 145 [3%] vs 58 [7.3%] vs 7 [8.6%], P < .001), prolonged ventilation (1652 [7.5%] vs 495 [10.2%] vs 153 [19.1%] vs 22 [27.2%], P < .001), and mortality (344 [1.6%] vs 132 [2.7%] vs 58 [7.3%] vs 9 [11.1%], P < .001). After risk adjustment, mild, moderate, and severe TR remained associated with increased morbidity and mortality (all P < .05). Increasing TR severity, although independently associated with higher surgical risk, is not accounted for entirely by STS risk calculator. This highlights the importance of TR on operative risk and supports consideration of concurrent tricuspid intervention for patients with significant TR undergoing CABG.

Current quality reporting methods are not adequate for salvage cardiac operations

ObjectivesOutcomes in cardiac surgery are benchmarked against national Society of Thoracic Surgeons (STS) data and include patients undergoing elective, urgent, emergent, and salvage operations. This practice relies on accurate risk adjustment to avoid risk-averse behavior. We hypothesize that the STS risk calculator does not adequately characterize the risk of salvage operations because of their heterogeneity and infrequent occurrence. MethodsData on all cardiac surgery patients with an STS predicted risk score (2002-2017) were extracted from a regional database of 19 cardiac surgery centers. Patients were stratified according to operative status for univariate analysis. Observed-to-expected (O:E) ratios for mortality and composite morbidity/mortality were calculated and compared among elective, urgent, emergent, and salvage patients. ResultsA total of 76,498 patients met inclusion criteria. The O:E mortality ratios for elective, urgent, and emergent cases were 0.96, 0.98, and 0.93, respectively (all P values > .05). However, mortality rate was significantly higher than expected for salvage patients (O:E ratio, 1.41; P = .04). Composite morbidity/mortality rate was lower than expected in elective (O:E ratio, 0.81; P = .0001) and urgent (O:E ratio, 0.93; P = .0001) cases but higher for emergent (O:E ratio, 1.13; P = .0006) and salvage (O:E ratio, 1.24; P = .01). O:E ratios for salvage mortality were highly variable among each of the 19 centers. ConclusionsThe current STS risk models do not adequately predict outcomes for salvage cardiac surgery patients. On the basis of these results, we recommend more detailed reporting of salvage outcomes to avoid risk aversion in these potentially life-saving operations.

“What’s the Risk?” Assessing and Mitigating Risk in Cardiothoracic Surgery

“What’s the Risk?” Assessing and Mitigating Risk in Cardiothoracic Surgery

Invited Commentary

It’s not the years…it’s the mileage.Indiana Jones, Raiders of the Lost Ark, 1981Sorabella and colleagues [1Sorabella R.A. Wu Y.S. Bader A. et al.Aortic root replacement in octogenarians offers acceptable perioperative and late outcomes.Ann Thorac Surg. 2016; 101: 967-973Abstract Full Text Full Text PDF Scopus (12) Google Scholar] present a small series (n = 34) of octogenarians undergoing aortic root replacement between 2005 and 2012 and compare the early and late outcomes with a larger (n = 592) contemporaneously operated cohort of younger patients. The authors found “moderately worse but acceptable perioperative mortality and late survival” among the older cohort and reasonably concluded that further studies are needed “to determine which subset of octogenarians are at the highest operative risk and may benefit from a conservative approach.” Despite the fact that age greater than or equal to 80 years was not associated with the composite outcome of in-hospital death or stroke in this underpowered study, more robust data such as those from Williams and colleagues [2Williams J.B. Peterson E.D. Zhao Y. et al.Contemporary results for proximal aortic replacement in North America.J Am Coll Cardiol. 2012; 60: 1156-1162Abstract Full Text Full Text PDF PubMed Scopus (133) Google Scholar] on nearly 46,000 patients undergoing proximal aortic operations (including more than 17,000 root replacements) in North America and captured in The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database found age greater than 70 years to be a significant predictor of both mortality and major morbidity among patients undergoing elective repair; risk increased further with each additional 5-year increment after 70 years. However, this does not mean that we should deny aged patients otherwise indicated complex open aortic operations but rather, as Sorabella and colleagues suggest, we should select our patients wisely. Unfortunately, the STS risk calculator does not provide guidance in this regard at the present time because aortic procedures are not currently modeled. However, sound clinical judgment, including assessment of other predictors of adverse outcome with proximal aortic operations as demonstrated in the Williams study [2Williams J.B. Peterson E.D. Zhao Y. et al.Contemporary results for proximal aortic replacement in North America.J Am Coll Cardiol. 2012; 60: 1156-1162Abstract Full Text Full Text PDF PubMed Scopus (133) Google Scholar]—such as chronic kidney disease, severe lung disease, New York Heart Association class IV heart failure, redo procedures, or previous coronary bypass grafting—as well as published frailty assessments [3Ganapathi A.M. Englum B.R. Hanna J.M. et al.Frailty and risk in proximal aortic surgery.J Thorac Cardiovasc Surg. 2014; 147: 186-191Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar] and the all-important “eyeball test” should lead us to select those octogenarians most fit for operation. When teaching our residents about risk assessment around surgical procedures, I often paraphrase the Indiana Jones quote at the beginning of this article that “it’s not the years but the miles,” with the point being that there are many “low-mileage” octogenarians fit for operation just as there are “high-mileage” younger patients who are unfit. As Sorabella and colleagues have shown, selection of these “low-mileage” older patients is possible, and their 81.9% actuarial 5-year survival demonstrates clear clinical benefit for this properly chosen cohort. Aortic Root Replacement in Octogenarians Offers Acceptable Perioperative and Late OutcomesThe Annals of Thoracic SurgeryVol. 101Issue 3PreviewAs the proportion of the population more than 80 years of age increases, cardiac surgeons will increasingly be consulted to operate on this high-risk patient group. The aim of this study is to evaluate the perioperative and late outcomes of octogenarians undergoing aortic root replacement in comparison with younger patients. Full-Text PDF

External validity of the Society of Thoracic Surgeons risk stratification tool for deep sternal wound infection after cardiac surgery in a UK population

Deep sternal wound infection (DSWI) is a devastating complication of cardiac surgery, with a historical incidence of 0.4-5%. Predicting which patients are at higher risk of infection may help instituting various preventive measures. Risk calculations for mortality have been used as surrogates to estimate the risk of deep sternal wound infection, with limited success. The Society of Thoracic Surgeons (STS) 2008 Risk Calculator modelled the risk of DSWI for cardiac surgical patients, but it has not been validated since its publication. We sought to assess the external validity of the STS-estimated risk of DSWI in a United Kingdom (UK) population. Using our prospectively captured database, we retrospectively calculated the risk of DSWI for 14 036 patients undergoing valve, coronary artery bypass grafts or combined procedures between February 2001 and March 2010. DSWI was identified according to the Centre for Disease Control and Prevention definition. The receiver operator characteristic (ROC) curve was employed to test the performance of the model using the area under the ROC curve (AUROC). The calibration of the model was interrogated using the Hosmer-Lemeshow test for Goodness of Fit. A total of 135 (0.95%) patients developed DSWI. Although there was a statistically significant difference in the calculated risk of patients who contracted DSWI (0.44% ± 0.01) vs those who did not (0.28% ± 0.00, P < 0.0001), the AUROC of 0.699 (95% confidence interval: 0.6522-0.7414) denoted a modest discriminatory power, with the Hosmer-Lemeshow Goodness of Fit statistic (P < 0.001) suggesting poor calibration. A risk-adjusted modifier improved the calibration (P = 0.08). The STS risk calculator lacks adequate discriminatory power for estimating the isolated risk of developing deep sternal wound infection in a UK population. The discrimination is similar to the tool's validation c-statistic and may have a place in an integrated calculator.

Comparison of original EuroSCORE, EuroSCORE II and STS risk models in a Turkish cardiac surgical cohort†

The aim of this study was to compare additive and logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE), EuroSCORE II and the Society of Thoracic Surgeons (STS) models in calculating mortality risk in a Turkish cardiac surgical population. The current patient population consisted of 428 patients who underwent isolated coronary artery bypass grafting (CABG) between 2004 and 2012, extracted from the TurkoSCORE database. Observed and predicted mortalities were compared for the additive/logistic EuroSCORE, EuroSCORE II and STS risk calculator. The area under the receiver operating characteristics curve (AUC) values were calculated for these models to compare predictive power. The mean patient age was 74.5 ± 3.9 years at the time of surgery, and 35.0% were female. For the entire cohort, actual hospital mortality was 7.9% (n = 34; 95% confidence interval [CI] 5.4-10.5). However, the additive EuroSCORE-predicted mortality was 6.4% (P = 0.23 vs observed; 95% CI 6.2-6.6), logistic EuroSCORE-predicted mortality was 7.9% (P = 0.98 vs observed; 95% CI 7.3-8.6), EuroSCORE II- predicted mortality was 1.7% (P = 0.00 vs observed; 95% CI 1.6-1.8) and STS predicted mortality was 5.8% (P = 0.10 vs observed; 95% CI 5.4-6.2). The mean predictive performance of the analysed models for the entire cohort was fair, with 0.7 (95% CI 0.60-0.79). AUC values for additive EuroSCORE, logistic EuroSCORE, EuroSCORE II and STS risk calculator were 0.70 (95% CI 0.60-0.79), 0.70 (95% CI 0.59-0.80), 0.72 (95% CI 0.62-0.81) and 0.62 (95% CI 0.51-0.73), respectively. EuroSCORE II significantly underestimated mortality risk for Turkish cardiac patients, whereas additive and logistic EuroSCORE and STS risk calculators were well calibrated.