What is the STS score?
The STS (Society of Thoracic Surgeons) score is a risk prediction model that estimates the probability of mortality and major complications after cardiac surgery. It uses patient-specific variables including age, sex, weight, comorbidities, cardiac function, and the planned procedure to calculate predicted risk. The STS Predicted Risk of Mortality (PROM) is the most widely used cardiac surgery risk score in the United States.
The complete answer.
The STS score considers approximately 40 patient variables and is calibrated against outcomes from millions of cardiac surgery cases in the STS National Database. An STS PROM of less than 3% is generally considered low risk, 3-8% is intermediate risk, and greater than 8% is high risk. These thresholds influence treatment decisions — for example, the 2020 ACC/AHA guidelines use STS score to help determine whether TAVR or surgical AVR is preferred for aortic stenosis patients. The STS also publishes hospital star ratings (1-3 stars) based on risk-adjusted outcomes.
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