Pre-operative MELD-Na score as an independent predictor of post-operative mortality after valve surgery in rheumatic valvular heart disease patients

BACKGROUND: Rheumatic heart disease (RHD) poses a significant global health challenge due to its high rates of premature morbidity, mortality, and disability, particularly in low-income countries. Existing risk scoring systems for valve replacement in cardiac surgery have primarily focused on non-RHD cases, making them less applicable to RHD patients due to the distinct pathology of valvular damage. This study aims to evaluate the Model for End-stage Liver Disease, including sodium (MELD-Na) score, as a predictive tool for pre-operative mortality risk assessment following cardiac surgery in RHD patients. METHODS: This retrospective cohort study was conducted at Tenwek Hospital in Kenya and included 93 patients who underwent open heart valve replacement surgery between March 2022 and March 2023. Patients who underwent mechanical mitral valve replacement (MVR), mechanical aortic valve replacement (AVR), and tricuspid valve repair surgery (TVr) were included. Data were collected from Tenwek Hospital's electronic medical record system, and statistical analysis was performed using IBM SPSS Statistics 27.0, including Chi-square and binary logistic regression. Operative mortality was defined as all deaths occurring during the hospitalisation period of the operation and within 30 days post-discharge, unless unrelated to the procedure. RESULTS: The study included a cohort of 93 patients, comprising 36 (38.7%) males and 57 (61.3%) females, with a median age of 25. The majority of patients presented with mitral valve disease, 63 (67.7%), with varying degrees of mitral regurgitation, 32 (34.4%) and mitral stenosis, 31 (33.3%). Notably, 43 (46.2%) of patients exhibited an elevated MELD-Na score falling within the range of 9-15, while 20 (21.5%) had severely elevated scores exceeding 15. The overall mortality rate was 10 (10.8%), with a majority, six (60%), of deaths occurring in patients with severely elevated MELD-Na scores and the remaining 40% in the moderate category. Logistic regression analysis was employed to compare the predictive value of MELD-Na score with EuroScore II as a baseline indicator. Subsequently, the analysis was repeated, incorporating individual components of the MELD-Na score. The results indicated a significant link between the MELD-Na score and operative mortality (p = 0.003), showing an odds ratio (OR) of 1.17 (95% confidence interval (CI): 1.05-1.30). Additionally, both serum creatinine (p = 0.012, OR: 1.04, 95% CI: 1.02-1.09) and the international normalised ratio (INR) (p = 0.005, OR: 2.8, 95% CI: 1.38-6.0) emerged as notable predictors of operative mortality. CONCLUSION: Elevated MELD-Na scores are associated with an increased risk of operative mortality following RHD valve surgery, suggesting potential utility as a pre-operative risk stratification tool. Our findings underscore the utility of the MELD-Na score, particularly its components serum creatinine and INR, in predicting mortality risk following cardiac surgery in patients with RHD. Further prospective multicentre studies with larger sample sizes and longer durations are warranted to validate these findings.