The lone lifeline-a rare case report of a single right coronary circulation with hypoplastic left coronary system.

Background: Single coronary artery is an exceptionally rare congenital anomaly, occurring in ∼0.02% of patients undergoing coronary angiography. Hypoplastic coronary artery disease represents another uncommon congenital abnormality characterized by underdevelopment of epicardial coronary arteries. The coexistence of these anomalies resulting in a functionally single coronary circulation is extremely rare and has important diagnostic and clinical implications. Case summary: A woman in her late 60s presented with atypical chest pain. Electrocardiography and transthoracic echocardiography demonstrated normal findings with preserved biventricular function. Coronary angiography revealed an atretic left coronary ostium with retrograde filling of the left coronary system from the right coronary artery. Computed tomography coronary angiography confirmed a dominant right coronary artery supplying the entire myocardium with a hypoplastic left coronary system. The left anterior descending artery was opacified via collateralization through Vieussens' arterial ring. No obstructive coronary disease was identified. The patient was managed conservatively and remained clinically stable on follow-up. Discussion: Rare coronary artery anomalies may present with non-specific symptoms and require multimodality imaging for definitive diagnosis. Early recognition is crucial for appropriate risk stratification, management, and surveillance.