A Rare Anatomical Variant: Congenital Absence of the Right Coronary Artery with Left Circumflex Artery Supplying the Right Coronary Artery (RCA) Territory.

BACKGROUND While most coronary congenital anomalies are uncommon, comprising less than 2% of the general population, a single coronary artery is an especially rare finding within this broader category. It involves a lone vessel forming a single ostium from the aortic trunk. This vessel is then the source through which cardiac blood supply originates. Such congenital coronary artery anomalies are rare but can have clinically relevant consequences such as sudden death and other cardiac complications. Nonetheless, they are usually incidental findings and can be asymptomatic. This report discusses the case of a female patient found to have an absence of the right coronary artery, with the left circumflex supplying the right coronary artery territory. CASE REPORT We report a rare case of a 66-year-old woman who presented with substernal chest pain and shortness of breath. Vital signs, laboratory work-up, and resting electrocardiogram did not reveal an underlying etiology. However, an exercise stress test was positive. Left heart catheterization was performed and revealed a dominant left circumflex artery supplying the entire right coronary territory. Further imaging revealed the absence of a separate right coronary artery ostium. The patient was treated with a beta-blocker, high-intensity statin, and a nitrate. CONCLUSIONS Single left coronary artery, especially with the absence of the right coronary artery, is particularly rare, but can have significant clinical implications. Prompt diagnosis is important but challenging considering the variable presentation of this condition. It is important to review diagnostic modalities available and the treatment for patients.