APCU25CR2 A rare coronary variant: distinguishing congenital absence of the left circumflex artery from single coronary artery

Introduction Congenital coronary artery anomalies (CCAAs) are rare anatomical variants, identified in approximately 1% of the population. While most remain clinically silent, certain anomalies can predispose individuals to myocardial ischemia, arrhythmias, or sudden cardiac death. One such anomaly is the congenital absence of the left circumflex artery (LCx), reported in only 0.003% to 0.067% of cases. It must be carefully differentiated from a single coronary artery (SCA) anomaly, which presents a higher clinical risk and requires distinct management strategies.Case Presentation We report the case of a 59-year-old man with a history of obesity, hypertension, and heavy smoking, who presented with recurrent exertional chest discomfort radiating to the left arm and neck. The pain, rated 3–4/10, resolved with rest. Initial evaluation, including troponin levels and echocardiography, was normal. However, electrocardiography revealed Q waves and T-wave inversion in the inferior leads, along with ST-segment depression in lead aVL. Based on the European Society of Cardiology (ESC) criteria for chronic coronary syndrome (CCS), the patient was assessed as having moderate pre-test probability of obstructive coronary artery disease and was referred for coronary computed tomography angiography (CCTA).Result CCTA demonstrated a complete absence of the LCx. Perfusion of the lateral myocardial territory was maintained via a superdominant right coronary artery (RCA), with possible contribution from enlarged diagonal branches of the left anterior descending artery (LAD). No obstructive coronary lesions were identified. The patient was managed conservatively with beta-blockers, ACE inhibitors, aspirin, and high-intensity statins, along with counseling for smoking cessation and lifestyle modification.Discussion In this case, the absence of ST-segment elevation in lateral leads was attributed to adequate collateral supply. Although LCx agenesis is often considered benign, up to 20% of affected individuals may experience exertional angina due to reduced perfusion reserve or coronary steal. Importantly, occlusion of the compensatory RCA in such cases could mimic high-risk multi-vessel disease and significantly worsen prognosis.Conclusion This case underscores the importance of precise anatomical definition using advanced imaging. CCTA is invaluable for distinguishing LCx agenesis from SCA, preventing misdiagnosis, and guiding appropriate therapy. Alongside precise imaging, aggressive control of traditional risk factors remains essential for favorable long-term outcomes.