Retro-Aortic Anomalous Coronary Artery (RAC) Sign in a Sexagenarian

Anomalous coronary arteries are congenital anomalies characterized by an abnormal location of the coronary ostium and/or an atypical vascular course. While most cases are asymptomatic and remain undiagnosed, certain variants can be clinically significant, causing symptoms or even sudden cardiac death. A retro-aortic course of the coronary artery is generally considered to be benign, though rare instances have been reported to cause myocardial ischemia. This course can be detected on transthoracic echocardiogram (TTE) as a retro-aortic anomalous coronary artery (RAC) sign. The RAC sign is strongly associated with the detection of a retro-aortic coronary anomaly on cardiac computed tomography (CT) scans. Given its high specificity, its identification on TTE can be reliably documented as highly suggestive of an anomalous coronary artery in echocardiography reports. We report the case of a 67-year-old woman presenting with nocturnal syncope. TTE reported a tubular echogenic density in the atrioventricular (AV) groove. Coronary CT angiography (CCTA) showed an anomalous left circumflex coronary artery (LCx) arising from the right coronary cusp taking a retro-aortic course to the left AV groove. There were no high-risk anatomical features of the anomalous LCx or any significant coronary artery stenosis. Holter monitor revealed sinus pauses of up to nine seconds, correlating with her symptoms. She was diagnosed with sick sinus syndrome and a permanent pacemaker was implanted. She remained asymptomatic thereafter. The TTE finding, labeled as the RAC sign, correlated well with the anomalous LCx on the CCTA. The anomalous LCx was noted to be incidental and likely benign.