Scoring Systems for Predicting Mortality After Valve Surgery in the Philippines
The Society of Thoracic Surgeons (STS) score is the recommended scoring system for predicting mortality after valve surgery in the Philippines due to its superior calibration and discrimination specifically for valve procedures.
Primary Risk Stratification Systems
The STS score is the most appropriate scoring system for valve surgery risk assessment, as it was specifically designed for valve surgery with 24 covariates derived from a large database of patients undergoing isolated valve procedures 1
The STS score has demonstrated superior calibration (accuracy between predicted and observed outcomes) and discrimination (ability to distinguish between high and low-risk patients) for valve surgery compared to other scoring systems 2, 3
The European System for Cardiac Operative Risk Evaluation (EuroSCORE II) is an alternative option that has been updated to improve its performance in predicting mortality after valve surgery 4, 3
Components of STS Risk Score
The STS risk calculator incorporates patient demographics, comorbidities, cardiac function parameters, and procedure-specific factors to generate a predicted risk of mortality 1
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 1
For valve surgery specifically, the STS model accounts for the type of valve procedure (repair vs. replacement) and whether concomitant procedures such as CABG are planned 1
Performance of STS Score in Valve Surgery
The STS score has demonstrated good discrimination for predicting operative mortality after valve surgery with an area under the curve (AUC) of 0.81 in elderly patients 2
For isolated aortic valve replacement, the STS score shows better calibration than the logistic EuroSCORE, with a risk-adjusted mortality ratio of 1.05 (95% CI 0.30 to 1.79) compared to 0.34 (95% CI 0.10 to 0.58) for the logistic EuroSCORE 3
The STS score has also shown value in predicting not only perioperative mortality but also one-year and long-term survival rates after valve surgery 2
Enhancing Risk Prediction with Frailty Assessment
While the STS score provides good baseline risk assessment, combining it with frailty indices significantly improves mortality prediction after valve procedures 5
Frailty assessment should include evaluation of cognition, mobility, nutrition, and activities of daily living to complement the STS score 5
The combined model of STS score with frailty assessment has demonstrated superior discrimination (C-statistic 0.68) compared to STS score alone (C-statistic 0.64) 5
Practical Application in the Philippines
For Filipino patients undergoing valve surgery, the STS risk calculator should be used to estimate operative risk and guide clinical decision-making 1, 4
Individual risks should be calculated using the online STS risk calculator (http://209.220.160.181/STSWebRiskCalc261/) prior to valve procedures as part of the shared decision-making process 1
Risk assessment should be performed by the multidisciplinary heart team, with the STS score serving as an objective measure to guide discussions about procedural benefits versus risks 1
Limitations and Considerations
The STS score may not account for all risk factors relevant to the Filipino population, so clinical judgment should supplement the score 4
For patients undergoing transcatheter valve procedures, the STS score may need to be interpreted differently, as it was primarily validated for surgical procedures 1, 3
In high-risk patients, the STS score may be more accurate than the EuroSCORE, which tends to overestimate mortality in this population 1
Risk Thresholds for Clinical Decision-Making
Patients with STS score <3% are considered low-risk for surgical aortic valve replacement 1
Patients with STS score >8% are considered high surgical risk and may benefit from consideration of alternative approaches 1
For mitral valve repair for primary mitral regurgitation, an STS score <1% indicates low risk 1
STS scores >7.4 have demonstrated 75.0% sensitivity and 66.2% specificity for predicting hospital mortality after redo mitral valve surgery 6