Assessing operative mortality risk in cardiothoracic surgery: analysis of STS scores – a retrospective study

Background: Mortality risk assessment is vital for preoperative risk evaluation and resource allocation. This article presents a single-center comprehensive analysis of Society of Thoracic Surgeons (STS) scores and factors impacting outcomes in cardiothoracic surgery patients. It aims to assess the effectiveness of the STS risk score in predicting mortality. This retrospective cohort calculates STS scores for a diverse cohort of 3084 patients who underwent cardiac surgery between January 2010 and December 2016 at a Tertiary care Hospital in Pakistan. Stata-14 was used for the analysis. Results: Demographics analysis showed the mean age of the study population was 58 years. The predominance of males and the most common procedures were isolated coronary artery bypass graft, mitral valve replacement, and aortic valve replacement. Hypertension (68.5%) and diabetes (50.7%) were the most prevalent comorbid conditions, with a family history of coronary artery disease found in 46.7% of the patients. Mortality rates were higher for females (5.5% vs. 2.6%), the elderly (4.3% vs. 1.3%), those with mitral insufficiency (22%) and patients on adenosine diphosphate inhibitors (8.8%) for anticoagulation. Post-operative complications, including dialysis, stroke, prolonged ventilation and length of stay, were linked to higher mortality. An STS score ≥ 1.645 indicated a high mortality risk group with a 10.3% mortality rate. This cutoff had a sensitivity of 74.5% and specificity of 78.2%, contributing to an accuracy of 78.08%. Conclusions: The STS risk calculator demonstrated robust predictive performance in this cohort, supporting its utility in the local context.