Mediastinal mayhem: the challenges of incidental thoracic arteriovenous malformations-a case report.

Background: Arteriovenous malformations (AVMs) within the mediastinum are rare vascular anomalies. With the increasing number of coronary angiographies being performed, the number of incidentally found cases is rising. This presents challenges in terms of determining the appropriate treatment strategy. Case summary: We present the case of a 79-year-old man with aortic stenosis, experiencing functional dyspnoea and fatigue. Echocardiography showed a bicuspid aortic valve, and while left heart catheterization confirmed no significant coronary stenosis, it revealed a tortuous vessel originating from the circumflex artery (Cx), assumed to be heading toward the pulmonary circulation. The patient was scheduled for a surgical replacement of the aortic valve (SAVR). During the SAVR, the tortuous vessel was revealed to be a large, complex AVM located in the mediastinum. This increased both the duration of the surgery and the use of cardioplegia. Further, bleeding occurred per-operatively. Post-operatively, the patient developed tachy-brady syndrome and was treated with a pacemaker before discharge. Discussion: Due to the rarity of incidental AVMs in the middle/posterior mediastinum, no standard treatment protocol is available. This leaves clinicians and surgeons to manage the disease on a case-by-case basis, often with limited experience to guide their decisions. This patient case underscores the challenge of determining whether patients should be offered transcatheter aortic valve implantation (TAVI) or surgery. Furthermore, it highlights the intricate challenges that can arise when dealing with thoracic AVMs during cardiac procedures, emphasizing the importance of pre-operative awareness and tailored surgical approaches based on multidisciplinary discussions.