What is the preferred scoring system, STS (Society of Thoracic Surgeons) score or EuroSCORE 2, for predicting mortality after cardiac surgery?

STS Score vs. EuroSCORE II for Predicting Mortality After Cardiac Surgery

The Society of Thoracic Surgeons (STS) score is the preferred scoring system for predicting mortality after cardiac surgery due to its superior calibration and discrimination, particularly for valve procedures and combined procedures. 1, 2

Comparison of Risk Stratification Systems

• The STS score is specifically designed for valve surgery with 24 covariates, making it more specific to valve heart disease, though less user-friendly than EuroSCORE II 1
• EuroSCORE II is an updated version of the original EuroSCORE that was developed to improve performance in predicting mortality after cardiac surgery 2
• The STS score has demonstrated better discrimination than EuroSCORE II for predicting operative mortality after CABG (AUC = 0.81 vs. 0.77) 3
• For valve procedures, the STS score and EuroSCORE II show similar discrimination but different calibration properties 3

Components of Risk Scores

STS Score

• Incorporates patient demographics, comorbidities, cardiac function parameters, and procedure-specific factors 2
• Key variables include age, gender, functional status, previous cardiac surgery, left ventricular ejection fraction, pulmonary hypertension, renal function, and emergency status 2
• Accounts for the type of valve procedure (repair vs. replacement) and whether concomitant procedures such as CABG are planned 2

EuroSCORE II

• Includes patient-related factors (age, sex, chronic pulmonary disease, extracardiac arteriopathy, neurological dysfunction, previous cardiac surgery, serum creatinine, active endocarditis, critical preoperative state) 1
• Cardiac-related factors (unstable angina, left ventricular dysfunction, recent myocardial infarction, pulmonary hypertension) 1
• Operation-related factors (emergency surgery, surgery on thoracic aorta, post-infarct septal rupture) 1

Performance in Different Surgical Populations

• For isolated CABG, the STS score outperforms EuroSCORE II in both discrimination and calibration (O:E = 0.80 vs. 0.68) 3
• For aortic valve replacement (AVR), EuroSCORE II may be more accurate in calibration (O:E = 0.96 vs. STS-PROM: 0.76) 3
• For combined AVR+CABG procedures, the STS score has better discriminative ability for mortality (c=0.699) compared to EuroSCORE II (c=0.669) and original EuroSCORE (c=0.587) 4
• The STS score also performs better for predicting composite morbidity (c=0.627), stroke (c=0.642), prolonged ventilation (c=0.642), and return to theater (c=0.612) after AVR+CABG 4

Clinical Application

• For transcatheter aortic valve replacement (TAVR), EuroSCORE II and the STS score are better calibrated than the original logistic EuroSCORE, though all have only moderate discrimination 5
• Risk thresholds have been established: STS score <3% indicates low risk for surgical AVR, while >8% suggests high surgical risk 2
• For mitral valve repair for primary mitral regurgitation, an STS score <1% indicates low risk 2
• The 2021 ESC/EACTS guidelines recommend the use of EuroSCORE II or STS scores for risk stratification 6
• The 2021 ACC/AHA/SCAI guidelines specifically recommend the STS risk score for patients being considered for CABG 6

Strengths and Limitations

• The STS score performs better than EuroSCORE II in US populations, particularly for CABG procedures 3
• EuroSCORE II has better predictive discrimination for operative mortality than the original EuroSCORE, which greatly overestimated risk 7
• The inclusive nature of EuroSCORE II provides more flexibility for complex procedures not covered by the STS model 7
• Both scoring systems show declining predictive ability for medium-term mortality beyond the immediate postoperative period 8
• Neither score adequately accounts for frailty, liver cirrhosis, or malnutrition, which are important risk factors for cardiac surgery outcomes 6

Best Practices for Risk Assessment

• Risk scores should be calculated using online calculators prior to procedures as part of the shared decision-making process 2
• Risk assessment should be performed by a multidisciplinary heart team, with risk scores serving as objective measures to guide discussions 2, 6
• Risk scores should not be used in isolation but integrated with clinical judgment and other methods of risk assessment 1
• For complex cardiac surgical patients, EuroSCORE II should be considered due to its flexibility in accommodating numerous procedures 7