Assessing Mortality Risk in Cardiothoracic Surgery Patients: A Comprehensive Analysis of the Society of Thoracic Surgeons’ Scores – a Retrospective Cohort Study

Abstract Background: Mortality risk assessment is vital for preoperative risk evaluation and resource allocation. This article presents a single-centered comprehensive analysis of Society of Thoracic Surgeons (STS) scores and factors impacting outcomes in cardiothoracic surgery patients. It aims to assess the STS risk score's effectiveness in predicting mortality. Methods: STS scores for a diverse patient cohort of 3084 patients who underwent cardiac surgery between January 2010 and December 2016 at a Tertiary care Hospital, in a low-middle income country . Statistical methodologies, such as the chi-square test, Fisher's exact test, independent sample t-test and Mann-Whitney U test were applied. Univariate and multivariate analysis were also executed. Results: Demographics analysis showed the mean age of study population was 58 years. The predominance of males and the most common procedures were isolated Coronary Artery Bypass Graft (CABG), MVR, and AVR. Hypertension and diabetes were the most prevalent comorbid conditions, with a family history of CAD found in 46.7% of the patients. Mortality rates were higher for females, the elderly, those with mitral insufficiency and patients on ADP inhibitors for anticoagulation. Post-operative complications, including dialysis, stroke, prolonged ventilation and length of stay, were linked to higher mortality. The threshold value of STS was found to be ≥ 1.645 indicating a high-risk group with a 10.3% mortality rate. This threshold had a sensitivity of 74.5% and specificity of 78.2%, contributing to an accuracy of 78.08%. Conclusion: STS risk calculator is a great tool for mortality prediction in our country with an AUC value of 0.819 (95% CI 0.791-0.898).