Vascular Auto-Tamponade of an Infected (Mycotic) Aneurysm of the Aortic Arch and Innominate Artery

Background: Infected aortic aneurysms pose significant therapeutic challenges, given the fragility of infected aneurysmal tissue. Mycotic aneurysms caused by Streptococcus agalactiae are rare and may progress in the absence of classical systemic infection signs. Here, we discuss the surgical management of an unusual presentation of a mycotic aneurysm and its rapid progression with no incremental changes in the patient’s symptoms. Case: A 72-year-old woman presented with subacute general deterioration and back pain. A general workup revealed a mycotic aneurysm of the aortic arch, at the level of the brachiocephalic artery. Initial CT showed a 7 × 5.5 mm pseudoaneurysm that enlarged to 41 × 26 mm within three weeks, despite clinical improvement of her presenting symptoms on antibiotics. Given that the lesion progressed, a staged procedure, consisting of a left carotid–subclavian bypass followed by proximal arch repair, was undertaken with success. Intra-operatively, a completely thrombosed innominate vein was found compressing—and likely tamponading—the pseudoaneurysm, a phenomenon that may have prevented catastrophic rupture. A Dacron graft was sewn end-to-end to the distal ascending aorta; the posterior half of this distal anastomosis incorporated the rim of the innominate artery defect to create a single hemostatic suture line. Conclusions: This case demonstrates a benign initial presentation can degenerate into a catastrophic pseudoaneurysm and how rapidly progressive thoracic infected aneurysms can develop. Heightened clinical acumen is required for accurate diagnosis. Close follow-up is also suggested based on the rapid progression experienced by our patient. Serial imaging, rather than symptomatic or laboratory response alone, should guide the timing of intervention.