Isolated Obtuse Marginal Branch Occlusion Presenting as Recurrent Sinus Arrest without ST-segment Elevation

A 47-year-old man presented with dyspnea and presyncope. Initial electrocardiography showed sinus bradycardia without ST-segment elevation, whereas telemetry revealed recurrent sinus arrest with a maximum pause of 3.3 s. Emergency coronary angiography revealed total occlusion of the obtuse marginal branch. Although the sinoatrial node artery originated near the occlusion, intravascular ultrasound confirmed the preservation of blood flow. Immediate revascularization led to complete resolution of sinus arrest. This case suggests that isolated lateral wall ischemia may represent an unusual manifestation of the Bezold-Jarisch reflex without direct sinoatrial node artery involvement. Therefore, acute coronary syndrome should be considered in unexplained sinus node dysfunction, even in the absence of typical chest pain.