Mitral Regurgitation in Acute Anterior Versus Inferior ST-Elevation Myocardial Infarction: Prevalence, Severity, and 40-Day Outcomes in a Prospective Observational Cohort

Objectives: Ischemic mitral regurgitation (MR) is an important complication of acute ST-elevation myocardial infarction (STEMI) and may occur as a consequence of papillary muscle dysfunction, altered left ventricular geometry, and ischemic remodeling. The occurrence and severity of MR may vary according to infarct territory; however, contemporary data from Pakistani patients remain limited. To compare the prevalence and semiquantitative severity of MR between patients presenting with first acute anterior and inferior STEMI and to explore 40-day mortality according to infarct territory and MR status. Methodology: This prospective observational cohort study included 200 consecutive patients with first acute STEMI admitted to the Department of Cardiology, Allama Iqbal Memorial Teaching Hospital, Sialkot, comprising 100 patients with anterior STEMI and 100 with inferior STEMI. Transthoracic echocardiography was performed within 24 hours of admission. MR was detected using two-dimensional and color-flow Doppler echocardiography and semiquantitatively graded according to maximal regurgitant jet length. Patients were prospectively followed for 40 days to determine vital status. Between-group comparisons were performed using appropriate univariate tests, and multivariable binary logistic regression was used to identify factors independently associated with MR. Results: The mean age of the cohort was 44.81 ± 14.77 years, and 66.5% of participants were male. MR was detected in 63/200 patients (31.5%) and was significantly more frequent in inferior than anterior STEMI (40.0% vs 23.0%; χ²=5.932, p=0.015). Grade 1+ MR was the most frequent severity category, while the overall distribution of MR grades did not differ significantly between infarct territories (p=0.069). In multivariable analysis, inferior STEMI was independently associated with MR (aOR 2.17, 95% CI 1.15–4.10; p=0.017), as was female sex (aOR 1.97, 95% CI 1.03–3.77; p=0.039). Overall 40-day mortality was 8.5%. Mortality was numerically higher among patients with MR than those without MR (12.7% vs 6.6%), but the difference was not statistically significant (p=0.175). The study was not independently powered to evaluate mortality differences. Conclusion: MR was more frequently detected following inferior than anterior STEMI in this cohort, with mild MR representing the predominant semiquantitative grade. Inferior STEMI remained independently associated with MR after adjustment for demographic and clinical covariates. Although 40-day mortality was numerically higher among patients with MR, the difference was not statistically significant and should be considered exploratory. Larger multicenter studies incorporating standardized, integrative quantitative echocardiographic assessment are required to clarify the prognostic significance of ischemic MR following acute STEMI.