Left main coronary artery disease (LMCD) is mainly caused by atherosclerotic stenosis. However, obstructed left coronary cusp (LCC) can be a cause of LMCD as well as a cause of severe aortic regurgitation rarely.

A 62 year old woman with symptomatic severe aortic regurgitation was referred for aortic valve replacement. Preoperative coronary angiography (panel A) showed anomalous connection from the right coronary artery (RCA) to the proximal part of the left anterior descending coronary artery (LAD) with aneurysmal dilatation of the left main coronary artery (LMCA), which was separated from the aorta. The 16 slice computed tomography (Sensation 16, Siemens Medical System, Germany) with contrast agent (iodixanol) revealed an LMCA aneurysm separated distinctly from the aortic sinus (panel B). The aortic valve was composed of three cusps. However, the LCC was hypoplastic and fused to the aortic wall on the operative finding (panels C and D). The left aortic sinus was reconstructed after incision of the LCC. The patient underwent aortic valve replacement with 21 mm On-X valve (Medical Research Carbon Institute, Texas, USA) and was discharged without complication.

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(A) Coronary angiography in left anterior oblique 45° and caudal 30° projection shows the aneurysmal dilatation (*) of the left main coronary artery (LMCA). 1, anomalous connection from the right coronary artery to the left anterior descending coronary artery (LAD); 2, LAD; 3, left circumflex artery and aorta (Ao). (B) Curved multiplanar reformation along the left coronary artery via 16 slice computed tomography demonstrates the LMCA aneurysm (*). Operative findings show a hypoplastic left coronary cusp with fusion to the aortic wall (C, D).