Asian Journal of Cardiology Research

Background: Almost 40% of patients with acute coronary artery occlusion present without the typical ST-elevation myocardial infarction (STEMI) criteria on an electrocardiogram (ECG), which delays revascularisation treatment and increases morbidity and mortality. However, many of these patients can be identified using other ECG criteria and emerging imaging modalities.

Aim: This study examined electrocardiographic (ECG) patterns associated with obtuse marginal and diagonal branch occlusion, focusing on cases without ST elevation in lead aVL.

Material and Methods: This retrospective analysis included patients with myocardial infarction (MI) related to obtuse marginal or diagonal branch occlusion who underwent coronary angiography within 12 hours of the onset of chest pain. The high lateral wall of the left ventricle is supplied by both the first diagonal and first obtuse marginal branches. Lead aVL represents this segment on the ECG. According to the ECG changes, patients were divided into two groups: Group 1, ST elevation in aVL ± I; and Group 2, no ST elevation in aVL ± I. The study was conducted from January 2023 to December 2025 at Istanbul Atlas University, Istanbul, Turkey.

Results: The study included 42 patients with myocardial infarction related to obtuse marginal or diagonal branch occlusion and angiographic TIMI flow of 0–1. Thirty-one patients (74%) had ST-elevation myocardial infarction (STEMI) in lead aVL. Of these, 18 patients had obtuse marginal branch occlusion and 13 had diagonal branch occlusion. Eleven patients (26%) had non-ST-elevation myocardial infarction (NSTEMI) with obtuse marginal branch occlusion. The ECG changes in patients with STEMI and obtuse marginal or diagonal branch occlusion included ST elevation in aVL ± I with ST deviation in lead V2. The 11 patients with obtuse marginal branch occlusion who did not fulfil the STEMI criteria showed the following findings: aVL QRS amplitude ≤ 5 mm, R wave in V2 ≥ aVL QRS amplitude, and V3, V2 T-wave area ≥ T-wave area (I + aVL).

Conclusions: Patients with NSTEMI due to total or subtotal obtuse marginal branch occlusion with TIMI flow of 0–1 showed several ECG changes despite the absence of ST-segment elevation on an otherwise normal ECG. These ECG criteria could improve diagnostic accuracy for high-lateral-wall myocardial infarction involving total occlusion of the obtuse marginal or diagonal branch, thereby facilitating early recognition and rapid reperfusion.