The South African Flag Sign: A Key Indicator of Acute D1 Occlusion

The South African flag sign (SAFS) on an ECG suggests an occlusion in the first diagonal branch of the left anterior descending (LAD) coronary artery, particularly in the context of acute chest pain. Due to its unique findings, it is often overlooked or misidentified. We present four cases in which this finding was identified on ECG, along with the corresponding angiographic images and clinical details. Two of these had an acute diagonal branch occlusion, which was treated with stent insertion. The other two cases had some angiographic changes but had no stent inserted. All of these cases showed a varying degree of left ventricular dysfunction and troponin rise, highlighting the importance of recognition and prompt management. On subsequent cardiac MRI, one patient was determined to have an aborted infarct, and another was suspected of the same. The urgency with which the SAFS should be expedited to invasive imaging should match that of other acute signs of occlusion, such as the new left bundle branch block (LBBB) in the context of chest pain. Increased awareness of the SAFS can prevent these cases from being overlooked and improve patient outcomes by ensuring they receive timely care.