Predicting Mortality After Cardiac Surgery with STS Score and EuroSCORE II

Introduction to Risk Stratification

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

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 incorporates patient demographics, comorbidities, cardiac function parameters, and procedure-specific factors 2
Key variables in the STS score include age, gender, functional status, previous cardiac surgery, left ventricular ejection fraction, pulmonary hypertension, renal function, and emergency status 2
The STS score 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
EuroSCORE II also includes cardiac-related factors (unstable angina, left ventricular dysfunction, recent myocardial infarction, pulmonary hypertension) 1
Operation-related factors in EuroSCORE II include emergency surgery, surgery on thoracic aorta, post-infarct septal rupture 1

The American College of Cardiology recommends the use of the STS risk score for patients being considered for CABG 4
The European Society of Cardiology and European Association for Cardio-Thoracic Surgery recommend the use of EuroSCORE II or STS scores for risk stratification 3
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

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, 3
Risk scores should not be used in isolation but integrated with clinical judgment and other methods of risk assessment 1
Neither the STS score nor EuroSCORE II adequately accounts for frailty, liver cirrhosis, or malnutrition, which are important risk factors for cardiac surgery outcomes 4