Large fusiform aneurysm of the superior vena cava: CT findings

A 62-year-old man presented complaining of atrial fibrillation.  Plain chest radiography and contrast-enhanced computed tomography (CT) revealed a large fusiform aneurysmal dilatation of the upper segment of the superior vena cava (SVC) without evidence of rupture, thrombosis, or pulmonary embolism. It was decided to treat the patient conservatively with follow-up imaging recommended.

Case presentation

A 62-year-old male patient complaining of atrial fibrillation was referred for pre-ablation workup. Plain chest radiography demonstrated a right paratracheal soft tissue shadow mimicking a mediastinal mass (figure 1). Contrast-enhanced computed tomography (CT) revealed fusiform aneurysmal dilatation of the upper segment of the superior vena cava (SVC) starting from its origin at the confluence of the right and left brachiocephalic veins and ending 3 cm above the cavo-atrial junction (figure 2), with maximal axial dimensions 6.5 x 5 x 6 cm. The azygous vein was seen to drain into the lower part of the aneurysmal SVC. There was no evidence of complications such as rupture, thrombus formation or pulmonary embolism. The patient was reassured and managed conservatively with follow-up imaging recommended.

Discussion

Congenital aneurysms of the SVC are very rare findings caused by congenital weakness of the venous wall or absence of the longitudinal muscle layer.¹ Congenital aneurysms are more commonly fusiform, while saccular aneurysms are thought to be post-inflammatory or resulting from trauma or intervention. In most described cases, the cause is unknown.^2,3 Most SVC aneurysms are asymptomatic, discovered incidentally during chest X-ray, simulating mediastinal mass. They may be associated with a ruptured aneurysm, or thrombosis and subsequent pulmonary embolisation.^2,3 There are no established guidelines for the management of SVC aneurysms but it is generally influenced by aneurysm type and size. Most fusiform aneurysms are managed conservatively with follow-up imaging since complications are uncommon. Prophylactic anticoagulation may be given to prevent thrombosis. Saccular aneurysms, on the other hand, are usually candidates for surgical resection even if asymptomatic, due to the higher risk of rupture or thrombosis. Development of symptoms or complications or significant aneurysm growth on follow-up may warrant interventions.^2,3

Conflicts of interest

None declared.

Funding

None.

Patient consent

Patient consent was obtained for anonymous publishing of images.

References

1. Sonavane SK, Milner DM, Singh SP, et al. Comprehensive imaging review of the superior vena cava. Radiographics 2015;35:1873–92. https://doi.org/10.1148/rg.2015150056

2. Soares Souza LV, Souza Jr AS, Morales MM, Marchiori E. Superior vena cava aneurysm: an unusual mediastinal mass. Eur J CardioThorac Surg 2021;5:276–7. https://doi.org/10.1093/ejcts/ezaa271

3. Kapoor H, Gulati V, Pawley B, Lee JT. Massive fusiform superior vena cava aneurysm in a 47-year-old complicated by pulmonary embolism: a case report and review of literature. Clin Imaging 2022;81:43–5. https://doi.org/10.1016/j.clinimag.2021.08.008