South African flag sign facilitating early recognition of acute first diagonal occlusion in a complex non-left main coronary bifurcation lesion: A case report

Abstract

The South African flag sign is an uncommon electrocardiographic pattern characterized by ST-segment elevation in leads I, aVL, and V2, with reciprocal ST-segment depression in the inferior leads, suggesting acute occlusion of the first diagonal (D1) coronary artery. This case report aimed to highlight the diagnostic value of this sign and describe the intravascular ultrasound (IVUS)-guided management of a complex non-left main coronary bifurcation lesion. A 53-year-old man presented with acute chest pain and diaphoresis of one-hour duration. The electrocardiogram demonstrated the South African flag sign, prompting immediate activation of the ST-segment elevation myocardial infarction protocol. Transthoracic echocardiography revealed anterior and anterolateral wall hypokinesia, with a left ventricular ejection fraction of 54%. Emergency coronary angiography demonstrated 70–80% stenosis of the proximal-to-mid left anterior descending (LAD) artery and complete thrombotic occlusion of the D1 branch, whose ostium was initially obscured. After successful guidewire crossing, a critical 95% ostial D1 stenosis was identified. IVUS was used to assess vessel dimensions and plaque morphology and to guide treatment of the Medina 1-1-1 bifurcation lesion. A provisional one-stent crossover strategy was performed using a drug-eluting stent in the LAD across the D1 bifurcation, followed by proximal optimization, kissing balloon inflation, and repeat proximal optimization. Final angiography showed restoration of coronary flow without significant residual stenosis or procedural complications. The patient remained free of recurrent ischemic symptoms at the two-week follow-up. This case demonstrates that recognition of the South African flag sign can facilitate early localization of D1 occlusion, particularly when the branch ostium is angiographically obscured. IVUS-guided provisional stenting may support procedural planning and optimization in complex non-left main coronary bifurcation lesions.