Unprotected left main coronary artery (LMCA) disease presenting with STEMI represents one of the most critical emergencies in interventional cardiology. The LMCA supplies the majority of the left ventricular myocardium; therefore, significant stenosis or occlusion can rapidly lead to extensive ischemia, hemodynamic collapse, and a markedly increased risk of in-hospital mortality. Although primary percutaneous coronary intervention (PCI) has become the cornerstone of reperfusion therapy for ST-elevation myocardial infarction (STEMI). Patients often arrive in cardiogenic shock, with multivessel disease, severe left ventricular dysfunction, or requiring advanced mechanical circulatory support. Understanding the epidemiology, clinical manifestations, and laboratory/imaging characteristics of this high-risk population is essential to improving early recognition and timely management. Therefore, this study aims to determine the prevalence and clinical features of LMCA-related STEMI among patients undergoing coronary intervention.

This retrospective study was conducted at Cho Ray Hospital and included all patients presenting with acute myocardial infarction due to left main coronary artery disease from January 2020 to December 2024. Clinical variables collected were age, sex, BMI, comorbidities, Killip class, length of stay, and total hospitalization time. Laboratory data included renal and hepatic function and lipid profile. Angiographic characteristics assessed coronary anatomy, number of diseased vessels, lesion classification, MEDINA bifurcation type, TIMI flow, presence of chronic total occlusion, thrombus burden, and collateral circulation. Procedural details recorded the target vessel (LAD, LCx, RCA, or Ramus), PCI strategy, stent deployment results, and use of adjunctive techniques such as IVUS, kissing-balloon inflation, and intra-aortic balloon pump support. Acute complications including cardiac arrest, stent thrombosis, pericardial effusion, and severe heart failure were systematically documented.

The cohort was predominantly composed of males (73/101) with the mean age was 64.7 +/- 10.8 . Patients showed a high burden of comorbidities: Hypertension (85.15%) , Dyslipidemia (84.16%) , Smoking (67.33%) , and Diabetes Mellitus (32.67%) . At presentation, NSTEMI (59.41%) was more common than STEMI (40.59%) , and the majority were classified as Killip I (57.43%), and Kiliip IV were 22.8%. Angiographic analysis highlighted a high rate of distal LMCA stenosis (78.22%) . All patients (100%) received a stent , achieving an excellent procedural success rate, with 99.01% obtaining favorable angiographic outcomes.Despite high technical success, the short-term outcomes were serious, the rate of Major Adverse Cardiovascular Events (MACE) was 11.88%, and cardiac mortality was 8.91%. Other complications included Acute Kidney Injury (17.82%) and Arrhythmias (17.82%). Crucially, multivariable logistic regression identified several independent predictors of increased mortality: higher Killip class on admission (OR 1.07, CI 95% 1.02-1.12, p=0.010) , the presence of arrhythmias (OR 1.23, CI 95% 1.05 - 1.42 , p=0.008) , STEMI presentation (OR 1.18, CI 95% 1.05-1.32, p=0.004) , and lower platelet count (OR 0.999, CI 95% 0.99-0.99 p=0.013) . Traditional cardiovascular risk factors like EF, dyslipidemia, hypertension, and diabetes did not show a significant independent association after adjustment.

In patients presenting with left main–related acute myocardial infarction, higher Killip class on admission, the presence of arrhythmias, STEMI presentation, and lower platelet count emerged as strong and independent predictors of mortality. These findings underscore the critical importance of early hemodynamic risk stratification, prompt rhythm management, and close monitoring of platelet levels to identify high-risk individuals and potentially guide more aggressive therapeutic strategies.