Imaging description

Coronary artery aneurysms are defined as localized vessel dilatation exceeding 50% of the adjacent normal coronary artery diameter. A precise definition of the threshold between aneurysm and “giant” aneurysm is not well established, but some authors have suggested that aneurysms > 20 mm meet this criteria. Giant coronary artery aneurysms are identified by the presence of a round or ovoid structure on the epicardial surface of the heart in the typical location for coronary arteries. Often discovered incidentally on echocardiogram, they will appear as a paracardiac mass with varying degrees of flow on Doppler interrogation depending on presence of thrombus. On non-contrast CT, they are low- attenuation, rounded masses that may have peripheral calcifications related to atherosclerosis. After contrast administration, lesions will enhance similar to blood pool, although varying degrees of thrombosis may be present (Figure 38.1). Large aneurysms can erroneously appear thrombosed on cardiac CT due to incomplete filling at the time of arterial phase acquisition (Figure 38.2). Delayed venous images will demon- strate further fill-in of the aneurysm. Cardiovascular magnetic resonance (CMR) imaging will typically show low signal on dark blood images due to flow (Figure 38.1). Steady-state free precession (SSFP) and contrast injections with gadolinium will confirm high signal in the structure due to blood and may show evidence of thrombus (Figures 38.1 and 38.2).

Importance

Patients with giant coronary aneurysms may present with life-threatening tamponade due to rupture. Thrombosis, fistulization to cardiac chambers, and embolization have also been noted in the literature. Giant coronary artery aneurysms can be misinterpreted as cardiac tumors, particularly if only limited imaging is available. The distinction between tumor and aneurysm could have significant impact on treatment.

Typical clinical scenario

Coronary artery aneurysms more commonly affect males and have an incidence between 0.3% and 5%. Coronary aneurysms greater than 20 mm are extremely rare and in one series represented only 0.02% of patients undergoing cardiac surgery. They are more likely to involve the right coronary artery.