STS Risk Score Interpretation and Management

Introduction to STS Risk Score

The American College of Cardiology recommends that an STS risk score >5% should trigger Heart Team evaluation and consideration of alternative approaches, as it indicates high risk for cardiac surgery patients, with the score being a validated tool that estimates operative mortality and morbidity 1, 2

For patients with an STS score >5%, the American College of Cardiology suggests convening a multidisciplinary Heart Team to determine the optimal revascularization or valve replacement strategy, including the primary cardiologist, interventional cardiologist, cardiac surgeon, and the patient 1, 2
The American College of Cardiology recommends calculating the precise STS score using the online calculator before any treatment decision for CABG candidates with STS >5% 1
The European Heart Journal suggests that for aortic valve replacement candidates with STS >8%, transcatheter aortic valve replacement (TAVR) should be strongly considered over surgical AVR 3

The American College of Cardiology notes that the STS score has major blind spots, including frailty, liver cirrhosis, and severe malnutrition or cachexia, which can lead to catastrophic outcomes if ignored 1, 2
The European Heart Journal recommends that expected survival <1 year from non-cardiac causes should be considered when evaluating patients with high STS scores 3

For STS 5-8% (intermediate-high risk), the American College of Cardiology recommends proceeding with detailed Heart Team discussion 1
For STS 8-15% (high risk), the European Heart Journal suggests that TAVR should be strongly considered for aortic stenosis over surgical AVR 3
For STS >15% (extreme risk), the European Heart Journal notes that this threshold suggests potential futility if life expectancy <1 year or severe functional limitations exist 3

The American College of Cardiology states that the STS score demonstrates excellent discrimination for adverse outcomes, superior to EuroSCORE II for CABG patients, especially at mortality rates >5% 1, 2

The American College of Cardiology warns against using the STS score as the sole determinant of operability, as it must be integrated with clinical judgment and assessment of factors the score doesn't capture 2, 4
The American College of Cardiology advises against assuming the score predicts quality of life improvement or return to independent living, as it only estimates short-term operative risks 4, 5
The European Heart Journal recommends considering local surgical expertise and outcomes when applying the STS score, as institutional experience significantly impacts actual mortality 3

The American College of Cardiology recommends calculating the STS score for all patients being considered for coronary artery bypass grafting (CABG) to facilitate informed consent regarding risks, benefits, and alternatives, with the STS Risk Calculator providing objective, validated estimates of operative risk for individual patients undergoing CABG and valve procedures based on clinical factors 6
The STS score demonstrates excellent predictive value for estimating risk of adverse events and performs better than EuroSCORE II for CABG patients, particularly at higher (>5%) predicted mortality rates, with annual calibration to ensure predicted rates equal observed rates 6

The American Heart Association defines low risk as STS-PROM <3%, intermediate risk as 3-8%, high risk as ≥8%, and extreme risk as ≥15%, with an STS-PROM score >15% indicating potential futility of transcatheter aortic valve replacement (TAVR) 7

The American College of Cardiology states that the STS score is essential for Heart Team discussions to determine optimal treatment strategy between surgical and transcatheter approaches for aortic valve replacement, guiding selection between percutaneous coronary intervention (PCI) versus CABG 6, 8
The European Society of Cardiology recommends using the STS score to guide selection between PCI and CABG, allowing clinicians, patients, and families to have reasonable estimates of operative risk 8

The American College of Cardiology notes that the STS score has significant limitations and does not adequately account for frailty, liver cirrhosis, malnutrition, end-stage renal disease, advanced oxygen-dependent lung disease, slow ambulation, severe pulmonary hypertension, advanced dementia, or severe cachexia, and should not be used in isolation but must be integrated with clinical judgment 6, 7, 9
Excluding patients from surgery based solely on higher risk derived from a single characteristic or the STS score alone is inappropriate, according to the American Heart Association 6