Validation of the MIDA mortality risk score in a surgical cohort of patients with primary mitral regurgitation

Abstract Background and aim The MIDA scale is a prognostic tool for stratification of short- and long-term mortality risk in patients with primary mitral regurgitation (PMR). The aim of this study is to validate the MIDA (1) score in our population of PMR treated with surgery. Methods Retrospective analysis of a prospective cohort of patients with PMR who underwent mitral valve surgery in a tertiary care center from 2014 to 2022. The necessary parameters for calculating the MIDA Score (age, symptoms, atrial fibrillation, left atrial diameter, right ventricular systolic pressure (RVSP), left ventricular end-systolic diameter (LVESD), and LV ejection fraction (LVEF)) were collected, and the MIDA score for each patient was calculated. Thereafter, patients were classified into seven different risk groups. One year and long-term mortality during follow-up were recorded. A logistic regression analysis was performed to evaluate the association of each parameter with outcomes. Finally, curves for the cumulative incidence of all-cause mortality according to the MIDA score were generated with the Kaplan–Meier method. Results A total of 349 patients were included. Mean age was 68.5 [12.4] years, 55.8% were male, and the median LVEF was 60% (55-65). Mean follow up was 3.28 (2) years. One year mortality occurred in 29 (8.3%) patients, and long-term mortality in 59 (16.9%). According to the MIDA score, the distribution of patients in each subgroup was as follows: score 0 (n=28), score 1-2 (n=35), score 3-4 (n=60), score 5-6 (n=99), score 7-8 (n=81), score 9-10 (n=35), score > 11 (n=11). Most of our cohort was classified as intermediate-risk patients, with a median score of 6 (3-8). In the univariable logistic regression analysis, age, symptoms before surgery and RVSP were the only MIDA parameters significantly associated with mortality (Table-Figure 1). In our population, the discriminatory capacity of the MIDA score, was moderate, with an area under the ROC curve of 0.676 CI (0.624-0.725) for one year mortality, and 0.702 (0.651-0.749) for long term mortality. The best cut-off point for predicting one-year and long-term mortality was a MIDA score of 7. Kaplan-Meier curves for mortality during follow-up are shown in Figure 2. Conclusions The MIDA score showed a fair discriminatory capacity in our surgical cohort of patients with PMR. Variables included in the score that had a significant association with mortality were age, presence of symptoms and elevated RVSP. LV parameters included in the MIDA, which are the current class I indication for surgery, did not show a significant association with outcomes. Different echocardiographic variables to evaluate cardiac damage in PMR are needed to achieve better stratification.Table-Figure 1Figure 2