Pathological dilatations of the coronary arteries are not exceptional and are called megadolichoartery, aneurysm or ectasia. Cases of marked arterial dilatation, although much rarer, are regularly reported following their discovery due to the impressive angiographic, echocardiographic or autopsy findings. However, their course, particularly in the long term, remains unclear. The authors report the case of a patient with a very large spindle-shaped aneurysm of the circumflex artery whose course was able to be followed over a period of ten years on three successive angiographic assessments performed for clinical coronary events. This follow-up was dominated by thrombosis of the aneurysm, extension of the aneurysmal disease and severe deterioration of left ventricular function.