Teaching Case

A 61-year-old man with systemic sclerosis was admitted to our institution for a recent onset of exertional dyspnea. An aneurysm of the right coronary artery (RCA) was observed as an occasional finding at high-resolution computed tomography (CT), without pulmonary fibrosis. Therefore coronary CT angiography was performed.

CORONARY CT ANGIOGRAPHY
A congenital absence of the left circumflex (LCX) coronary artery was detected (Figure A- B). The RCA originated normally from the right sinus of Valsalva and showed two atherosclerotic aneurysms (Figure C- D): a fusiform aneurysm between segment 1 and 2 (diameter of 14mm) and a giant fusiform aneurysm involving segment 3 (Figure E- F.) The latter had a maximum diameter of 24mm and showed a large eccentric thrombus with a residual lumen of 7 mm. Posterior descending artery and postero-lateral branches arose with normal aspect. The extremity of the RCA continued with a wide obtuse marginal branch (Figure E- G). The left anterior descending (LAD) coronary artery, arising from the left sinus of Valsalva, showed a uniform ectasia (diameter 5-6mm) (Figure H).
Follow-up was recommended for coronary artery aneurysms (CAA).

Agenesis of the LCX is an extremely rare condition (reported incidence 0, 003%) and only a few cases have been reported in the literature. Most of these are associated with chest pain, and few with myocardial infarction, dilated cardiomyopathy, or systolic click syndrome. Circumflex branch agenesis is considered a benign congenital anomaly if there are no significant coronary artery stenoses. [1, 2]
In our patient this rare anomaly was associated with another uncommon condition: CAA. Among these, giant CAA, defined as a coronary artery with a diameter more than 2cm, remain a rare pathology (reported incidence 0.02%).
CCA are usually diagnosed incidentally at echocardiography or angiography, and patients are usually asymptomatic. Alternatively, patients may present with complications due to thrombosis.
CCA commonly occur due to atherosclerosis, polyarteritis nodosa, inflammatory diseases or connective tissue diseases. [3]
The prognosis of CCA is usually favourable, but is directly related to the severity of the concomitant obstructive coronary artery disease.
Because of the rarity of this condition, there are no controlled clinical studies to evaluate optimal therapy for coronary artery aneurysms. Medical management depends on the presence or absence of coexisting obstructive coronary artery disease. In patients with coronary artery disease, treatment is guided by the underlying coronary artery stenosis. In the absence of obstructive coronary artery disease, treatment is not well established because it is based mainly on case reports and continues to be a therapeutic dilemma. Conservative measures consist of attempts to prevent thromboembolic complications. Surgery is indicated in patients with obstructive coronary artery disease or evidence of embolization leading to myocardial ischemia and in those patients with evidence of enlargement of saccular coronary artery aneurysms with increased risk of rupture. [4]
Coronary CT angiography is a useful technique to diagnose, evaluate and follow-up these coronary arteries abnormalities. The robust visualisation and classification of anomalous coronary arteries make CT angiography a first-choice imaging modality for the investigation of known or suspected coronary artery anomalies. Because of its three-dimensional nature, multidetector CT is well suitable to define the anatomical course of coronary arteries anomalies and their relationship to other cardiac and non-cardiac structures.