A Rare Case of Single Right Coronary Artery with Absent Left Main Coronary Artery

Abstract

A 54-year-old woman presented with abdominal pain and diarrhoea, and had new T-wave inversion on electrocardiogram in leads V2–V6. Past history included recurrent deep vein thrombosis/pulmonary embolism and a recent subtotal colectomy for ulcerative colitis. The patient denied chest pain and serial troponin I measurements were normal (<0.040 μg/L). Postoperative ileus was the likely cause of abdominal pain. Echocardiography revealed impaired left ventricular (LV) systolic function (LV ejection fraction 35–40%). Coronary angiography was performed and the left main coronary artery (LMCA) could not be located despite cuspal injections, ascending aortogram, and left ventriculogram. A dominant right coronary artery (RCA) was visualised, which passed around the left ventricular apex to the area normally supplied by the obtuse marginal, diagonal, and distal left anterior descending arteries. Computed tomography coronary angiography (CTCA) revealed a superdominant RCA supplying the LV apex and lateral wall with no LMCA coming off the left coronary cusp. The left circumflex was small and arose from a conus branch separate to the RCA. No significant stenosis was visualised on CTCA. The T-wave changes on electrocardiogram and subtle subendocardial enhancement/fibrosis in the anterior wall on cardiac magnetic resonance imaging were deemed to be secondary to supply–demand ischaemia, particularly at the distal end of the RCA, where it supplied the left anterior descending artery territory. The patient was discharged on metoprolol 25 mg twice daily and her usual warfarin. Single RCA with absent LMCA is extremely rare with only few isolated cases in the literature. Use of CTCA in combination with coronary angiography was useful in defining this unusual anatomy.