Bifascicular Block Associated With Myocardial Infarction: A Marker of Proximal Left Anterior Descending Artery Occlusion Confirmed by the Artificial Intelligence-Based Smartphone App Queen of Hearts.

In a clinical context highly suggestive of acute coronary syndrome (ACS), the presence of a bifascicular block (BFB) should be considered a potential ST-elevation myocardial infarction (STEMI) equivalent. A right bundle branch block (RBBB) may obscure accurate assessment of the ST segment, potentially masking ischemic changes. Therefore, in patients with suspected ACS, BFB (RBBB and left anterior fascicular block), whether new or pre-existing, should be managed as a high-risk finding and treated according to STEMI protocols if clinical suspicion is strong. We report the case of a man in his 70s with multiple cardiovascular risk factors who was admitted for chest pain and hypotension. The ECG revealed a new (or presumably new) BFB, consisting of RBBB and left anterior fascicular block, associated with QRS-concordant anterior ST-segment elevation extending to lateral leads. Urgent coronary angiography demonstrated a proximal left anterior descending (LAD) artery subocclusion, which was successfully treated with primary percutaneous coronary intervention and drug-eluting stent implantation. The artificial intelligence (AI)-based smartphone application Queen of Hearts (PMcardio) correctly interpreted this ECG pattern as a STEMI-equivalent, accurately identifying rhythm, conduction abnormalities, and predicting a reduced left ventricular ejection fraction. This case underscores the importance, within the appropriate clinical context, of early recognition of BFB as a STEMI-equivalent or occlusive myocardial infarction pattern, typically associated with proximal LAD occlusion, extensive myocardial injury, and poor prognosis. At the same time, it provides anecdotal evidence supporting the reliability and clinical utility of the AI-based Queen of Hearts app in ACS management.