FREQUENCY OF SIGNIFICANT LEFT MAIN CORONARY ARTERY INVOLVEMENT IN ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION (STEMI) VERSUS NON-ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION (NSTEMI)

Background: Left main coronary artery (LMCA) disease is a high-risk condition associated with significant morbidity and mortality in acute myocardial infarction (MI). While ST-segment elevation myocardial infarction (STEMI) often prompts emergent management, the burden of LMCA involvement in non-ST-segment elevation myocardial infarction (NSTEMI) remains under-recognized, despite its clinical relevance. Objective: To determine the frequency of LMCA involvement in MI and compare its prevalence between STEMI and NSTEMI patients. Methods: A cross-sectional study was conducted over six months at the National Institute of Cardiovascular Diseases (NICVD), Karachi. A total of 146 MI patients (≥18 years, both genders) diagnosed with STEMI or NSTEMI were included using non-probability consecutive sampling. LMCA involvement was defined angiographically as ≥70% luminal narrowing. Demographic data, clinical characteristics, and angiographic findings were recorded and analyzed using SPSS v25. Chi-square and Fisher's exact tests were used to compare LMCA frequency between groups, with p ≤ 0.05 considered significant. Results: Out of 146 patients, 83 (56.8%) had STEMI and 63 (43.2%) had NSTEMI. Overall, LMCA involvement was identified in 48 (32.9%) patients. Among STEMI patients, 28 (33.7%) had LMCA involvement, compared to 20 (31.7%) in the NSTEMI group (p = 0.78). No statistically significant difference was found across major demographic or clinical subgroups. Confidence intervals confirmed overlapping prevalence between the groups. Conclusion: LMCA involvement is common in both STEMI and NSTEMI, with no significant difference between the two. Early angiographic evaluation should be considered for all MI patients to ensure appropriate risk stratification and timely management.