A 53-Year-Old Man With Non-Exertional Chest Discomfort

A 53-year-old man with multiple cardiac risk factors but no previously documented coronary artery disease reports intermittent, non-exertional chest discomfort during a routine visit to his primary physician. A stress test with imaging is performed. This study does not reveal any electrocardiogram (ECG) or perfusion abnormalities with diagnostic workload. The patient's symptoms persist, and he undergoes cardiac catheterization at an outside hospital. The report of this study indicates that no epicardial stenoses are visible, but that aneurysms are present in the left anterior descending (LAD) artery and the right coronary artery (RCA). Shortly after this study is performed, the patient is started on a beta-blocker, aspirin, and warfarin and is referred for further management.

The patient's symptoms improve after initiation of medical therapy but do not disappear. His physicians, therefore, perform cardiac computed tomography angiography (CTA), which confirms that the proximal LAD contains a large, eccentric aneurysm extending to the first diagonal branch (Figure 1). The maximum luminal diameter of the aneurysmal segment was 15 mm. A mural thrombus was present, and the maximum external diameter of this segment was 27 mm. Focal aneurysms <10 mm in diameter were also observed in the left circumflex artery. The RCA was diffusely ectatic along its entire length, with a maximum diameter of 12 mm. There was no evidence of atherosclerotic disease.

Figure 1: Coronary Artery Aneurysms

Figure 1
Panel A contains a three-dimensional reconstruction of the CTA, in which the RCA and LAD artery are visible. The aneurysmal segment of the LAD is focal and is indicated with an arrow. The RCA contains a long, tubular aneurysm.
Panel B contains a curved reformat view of the LAD in which the aneurysmal segment is indicated with an arrow. The tip of this arrow is in contact with the outer wall of the aneurysm, which is separated from the inner lumen by mural thrombus.
CTA = computed tomography angiography; LAD = left anterior descending; RCA = right coronary artery.

A CTA of the head and neck is performed and reveals no arterial aneurysms or other vascular anomalies. A magnetic resonance angiogram of the chest confirms that the caliber of the thoracic aorta is normal with no aneurysmal segments. The proximal segments of the aortic branches are similarly normal in appearance. There are also no abnormalities in the visceral arteries or in the arteries of the extremities. In addition, none of these studies demonstrate any evidence of atherosclerotic disease. Extensive laboratory testing is performed, and molecular markers of connective tissue disease and active inflammation are negative.

Which of the following describes the most likely etiology of the coronary aneurysms in this patient?

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