Anomalous Left Circumflex Artery Originating From Right Coronary Cusp as Culprit Vessel in ST-Elevation Myocardial Infarction (STEMI)

Congenital coronary artery anomalies are rare. The most common anomalous variation is Anomalous Left Circumflex Artery (ALCx) which is a congenital anomaly. ALCx usually originates from the right sinus of Valsalva or as a proximal branching of the Right Coronary Artery (RCA). The clinical presentation has a spectrum which varies from asymptomatic presentation to angina or myocardial infarction with no atherosclerotic lesion due to kinking/compression of the vessel to ST-segment elevation myocardial infarction (STEMI) due to atherosclerotic occlusion. A 45-year-old female with a past medical history of hypertension, hyperlipidemia, type 2 diabetes, tobacco abuse, and a history of ischemic stroke, presented to the hospital due to chest pain. Electrocardiogram revealed inferior ST-elevation myocardial infarction (STEMI) and the patient was taken to the catheterization lab. Angiography revealed 90% stenotic Left Circumflex Artery (LCx) which was anomalous, arising from the right coronary cusp, whereas other coronary arteries were diffusedly atherosclerotic. A drug-eluting stent was placed in the ALCx reducing the stenosis from 90% to 0% and the patient was discharged in a stable condition on dual antiplatelet therapy and statin with plans for possible coronary artery bypass graft due to multivessel disease (severe diffuse disease of LAD, 90% mid-RCA stenosis, 80% proximal RCA stenosis). The patient was eventually lost to follow-up. Typically, anomalous LCx originating from RCA is benign, but there are many cases where there is myocardial infarction or sudden cardiac death due to acute angle take-off at the origin site. This anatomical variation is more important during cardiac surgeries because during valve replacement surgeries, there are cases of ALCx compression resulting in myocardial infarction. Our patient developed STEMI secondary to atherosclerotic stenosis in anomalous LCx. Based on her diffuse atherosclerotic disease and risk factors, it is likely that her anomalous anatomy did not cause her atherosclerotic disease. Overall, clinicians should remain vigilant for these anatomic abnormalities in their practice.