Emerging evidence challenges the traditional Acute Coronary Syndrome (ACS) classification, which distinguishes ST-elevation myocardial infarction (STEMI) from non-ST elevation myocardial infarction (NSTEMI)primarily based on electrocardiogram (ECG) and cardiac troponin levels. A growing body of research has revealed that a significant proportion of NSTEMI patients have an acute coronary occlusion (total or near total occlusion), termed occlusion myocardial infarction (OMI). This finding has crucial implications for refining treatment strategies, potentially necessitating more aggressive early interventions for certain NSTEMI cases.

This study aims to investigate the prevalence of occlusion myocardial infarction (OMI) in Non-ST elevation myocardial infarction patients and compare their clinical profile and short-term outcome with that of non-occlusion MI (non-OMI). This retrospective study was conducted by analyzing the electronic medical records of patients admitted to our hospital from October 2024 to December 2024. Only, straight forward cases of NSTEMI were selected for the study. Very elderly sick patients with comorbidities associated with troponin elevation were excluded.

A total of 200 patients (male vs. female 88% vs. 12%) were selected for study. Of these, 66(33%) patients had OMI and 134 (67%) were non-occlusive (p <0.0001;95% CI 24.4069% to 42.6869%). OMI patients were younger (52.7±3.4yrs vs. 57.8±2.7yrs; p0.0001). Multiple risk factors were comparable in OMI and non-OMI groups-Diabetes 54.5% vs. 49.3% (p 0.4827); Hypertension 72.7% vs. 76.1% (p 0.5522); Dyslipidemia 84.8% vs. 91% (p 0.1888); Smoking 27.3% vs. 28.4% (p 0.8732); CKD6.1% vs. 14.9% (p 0.0705). Past CAD/revascularization was more prevalent in non-occlusion MI (34.3% vs. 15.2%; p 0.0046) which was statistically significant.Peak Troponin-I level was statistically higher in OMI (26,225±10,449 vs. 5057±2354; p<0.0001). LV EF was comparable in both group (53.7±2.4% in OMI vs. 52.5±3.4%; p0.4338). Hospital arrival to PCI time was lower in OMI group (15.4±5hrs vs. 40.26±8.8hrs; p<0.0001) which was statistically significant. Major coronary artery involvement and PCI were more in non-occlusive group (82.1% vs. 66.7%; p0.0151) which was statistically significant.No hospital mortality occurred in OMI group whereas one patient in non-occlusion group who was brought following out of hospital cardiac arrest passed away (0% vs. 0.75%; p 0.4829). One month mortality was none in OMI group but one patient from non-occlusion group was readmitted with early stent thrombosis and cardiogenic shock who subsequently passed away (0% vs. 1.5%; p0.3201). Mortality rates were not statistically significant.

This retrospective study reveals that a substantial proportion (33%) of NSTEMI patients had total or near total occlusion of the culprit vessel. This was comparable to the rate reported in literature. Our study did not show any significant difference in short-term mortality or left ventricular function between occlusion myocardial infarction (OMI) and non-OMI groups. Several factors may have contributed to this outcome. Notably, OMI patients had less major coronary as culprit vessel, were younger, and underwent PCI more promptly than non-OMI patients, with shorter hospital arrival-to-PCI times. The proactive ED team's low threshold for activation of catheterization laboratory upon identifying high risk ECG features, combined with the availability of a 24-hour primary PCI team, likely played a crucial role in achieving timely interventions, particularly for high-risk patients with specific ECG characteristics. This study underscores the importance of timely diagnosis and efficient care in improving outcomes for NSTEMI patients, especially those with occlusive myocardial infarction. The integration of artificial intelligence can significantly enhance the detection of high-risk ECG features associated with occlusion myocardial infarction, potentially leading to more timely and effective intervention.