1346898 - Giant and full of clot – what to do now ? CMR in a giant thrombosed left main stem aneurysm

A 69 year old gentleman with a background of hypertension and hypercholesterolaemia was referred for CT thorax as part of a panel of investigations for tuberculosis. He recalled having suffered a non-specific illness aged 10, however was neither hospitalized nor investigated further at the time. CT thorax incidentally demonstrated an aneurysmal left anterior descending (LAD) artery. Based on this finding, he was referred to the local cardiac tertiary referral centre for further coronary assessment.

Diagnostic Techniques and Their Most Important Findings:

Gated CT coronary angiogram (CTCA; Fig. 1) was performed first which demonstrated a thick walled, aneurysmal dilatation of the left main stem (LMS), the inner diameter measuring 26mm and the outer diameter 55mm. There was marked focal mural thickening of the distal left circumflex artery (LCx) with focal dilatation within and marked mural thickening of the proximal right coronary artery. Invasive angiography was not performed due to the high risk of wall injury.

Upon review of the images and history in the heart team meeting, the LMS aneurysm was deemed likely longstanding following possible Kawasaki disease in childhood. He was referred for cardiovascular magnetic resonance (CMR) and commenced on anticoagulation for thrombus prevention.

CMR (Fig. 2) performed 8 months later demonstrated a giant LMS aneurysm measuring 92x65x69mm extending from the LMS ostium, with near complete resolution of luminal thrombus. The LCx was proximally dilated with resolution of original thrombus. There was mural thickening of the LAD and distal LCx suggestive of previous significant thrombus burden. Despite the large thrombus burden, there were only two small partial thickness infarcts in the LAD and LCx territory; the left ventricle size was normal sized with mildly impaired systolic function (Fig. 3).

As the patient was asymptomatic, no intervention was planned and a surveillance monitoring strategy was pursued, and he has been referred for assessment in a specialist Kawasaki clinic.
 

Learning Points from this Case:

While coronary angiography, optical coherence tomography and computed tomography remain the most widely applied imaging modalities in the assessment of coronary artery aneurysms (CAA) (1), CMR offers a comprehensive assessment of aneurysm size, thrombosis and mechanical complications in addition to myocardial function, fibrosis, and regional wall motion. This has been applied in the assessment of coronary involvement in systemic vasculitides, however can be utilised in CAA irrespective of aetiology.(2) A correlation between histopathological findings and myocardial injuries, their localisation and reversibility on contrast-enhanced CMR has been previously demonstrated.(3)  To this end, CMR can be applied in active surveillance of patients with CAA for myocardial involvement and contribute to decision-making with regards to timing and method of coronary intervention. Further studies are merited to establish CMR as a validated, non-invasive tool in the assessment of CAA and its sequelae.