A 48-year-old woman with no traditional coronary risk factors, presented to our hospital with a recent anterior ST elevation myocardial infarction which had been thrombolysed, from a local hospital. Her physical examination and routine investigations were unremarkable. A coronary angiogram (figure 1) revealed a saccular aneurysm arising from the left main coronary artery (LMCA). There were no stenotic lesions noted at the aneurysm site or elsewhere. A coronary intravascular ultrasound study demonstrated a wide-mouthed aneurysm in the LMCA measuring 3.5×4.5 mm, with no thrombus within (figure 2).

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Figure 1

Coronary angiography images in the cranial (A) and caudal (B) projections showing a saccular aneurysm arising from the left main coronary artery.

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Figure 2

Intravascular ultrasound images of proximal left main coronary artery (LMCA) (A) and distal LMCA with aneurysm (B).

Coronary artery aneurysms, are usually defined as dilatation of a segment of a coronary artery more than 1.5 times the normal size. Morphologically, they may be saccular or fusiform. The most common cause of coronary artery aneurysms is atherosclerosis. Other causes include Kawasaki disease, aortoarteritis or trauma;  coronary artery aneurysms can also be  mycotic, congenital or idiopathic. The reported incidence is about 1.65%, while LMCA aneurysms are rarer still with an incidence of 0.1% in a large angiographic series.1 Coronary artery aneurysms are prone to spasm, spontaneous dissection, intraluminal thrombus formation and distal embolisation which could lead to myocardial ischaemia or infarction. Therapy is largely guided by the presence of associated stenotic lesions. Treatment options include anticoagulation, covered stents and surgical options including reconstruction, resection and bypass surgery.2

This case highlights the fact that coronary artery aneurysms with intraluminal thrombus, may be an important cause of myocardial infarction. Recognition of this entity is vital, as long-term anticoagulation is essential in preventing future thrombotic events.