Objective: Acute ST-elevation myocardial infarcion (STEMI) due to left main coronary artery (LMCA) disease has high mortality rate. Advancements in stent technology have shown promising results in patients with unprotect- ed left main coronary artery (ULMCA) disease. SYNTAX score (SxS) is recommended to determine appropriate patients for revavascularization with PCI. However, predictive value of SxS in patients with STEMI who underwent primary PCI due to ULMCA disease has not fully been evaluated. Methods and Results: 53 patients with STEMI who underwent emergent PCI to a culprit LMCA lesion were en- rolled in this study. Patients were divided into three groups on the basis of their SxS; low (≤22; n = 14), inter- mediate ( 23–32; n = 14) and high (≥33; n = 25). During a follow-up of 3 years, SxS exhibited 62.2% sensitivity and 62.5% specificity for predictiıng development of MACE at a cut off value 28.25 (AUC: 0.731, P = 0.008), 70% sensitivity and 66.7% specificity for predicting mortality at a cut off value 31.25 (AUC:0.675, P = 0.034). At 3-year follow-up, the incidences of mortality, major adverse cardiac events (MACE) and targel vessel revascularization (TVR) were significantly higher in patients with high SxS group than in the intermediate and low SxS groups. In Kaplan–Meier survival analysis, survival rates of the low, intermediate, and high SxS groups were 91.7%, 78.6%, and 64.7%, respectively. Conclusions: Patients with acute STEMI who were treated with emergency PCI to a culprit ULMCA lesion, SxS is an important aid to deciding the appropriate revascularization strategy, can be derived quickly and repeatable.

Keywords: SYNTAX score LMCA disease ST elevation myocardial infarction