Prevalence and Early Left Ventricular Outcomes of Occlusive Myocardial Infarction in Non-ST-Elevation Acute Coronary Syndrome: A Retrospective Observational Study

Background and objective: Acute coronary syndromes are classified by the electrocardiogram (ECG) into ST-elevation myocardial infarction (STEMI) and non-ST-elevation types. However, many patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) have a fully blocked culprit artery, a condition called occlusive myocardial infarction (OMI). We aimed to find how common OMI is in an Indian NSTE-ACS cohort and to compare its early effects on heart function and survival with non-occlusive myocardial infarction (NOMI). Methods: In this retrospective observational study, 340 patients presenting within 24 hours of chest pain with NSTE-ACS who underwent coronary angiography at a tertiary cardiac centre were enrolled. OMI was defined angiographically as a totally or near-totally occluded culprit artery (Thrombolysis in Myocardial Infarction (TIMI) flow grade 0-1) and NOMI as grade 2-3. Left ventricular ejection fraction (LVEF) was measured at baseline and at three months, and all-cause death was recorded at 9-12 months. Logistic regression identified factors independently associated with OMI. Results: OMI was found in 112 of 340 patients (32.9%, 95% confidence interval (CI) 28.2-38.1%) and NOMI in 228 (67.1%). The two groups had similar baseline features and risk factors, but non-ST-elevation myocardial infarction (NSTEMI) was more common in the OMI group (83/112 (74.1%) vs. 140/228 (61.4%); p=0.028). OMI patients had a lower baseline LVEF (44.1 ± 11.4% vs. 49.2 ± 11.1%; p<0.001), which stayed lower at three months (50.4 ± 8.3% vs. 53.4 ± 8.5%; p=0.010) despite improvement in both groups. On regression, a lower baseline LVEF was the factor most strongly associated with OMI. Death rates were similar (1/88 (1.1%) vs. 6/175 (3.4%); p=0.49). Conclusions: About one in three NSTE-ACS patients undergoing coronary angiography in this single-centre, retrospective cohort had a blocked culprit artery, and this group had worse heart function at presentation and at three months despite similar baseline risk profiles. Given the retrospective, single-centre design and incomplete follow-up, these findings are hypothesis-generating: they support maintaining a high index of suspicion for a blocked artery in NSTE-ACS patients with reduced LVEF, but do not establish that earlier angiography improves outcomes in this subgroup.