A 66-year-old man was suddenly referred to the emergency department (ED) for an extra-hospital cardiac arrest due to ventricular fibrillation, promptly treated by a single DC shock. Four months prior, he had undergone aortic valve replacement with a biological valve prosthesis (BVP, Perimount Magna n. 23) for severe aortic stenosis. One month after cardiac surgery the patient was hospitalized for acute cholecystitis requiring antibiotics and percutaneous cholecystostomy. On arrival to the ED the patient was awake and completely asymptomatic; no fever during days before the episode. He had been complaining of constricting retrosternal chest pain during physical exertion for ten days. However, no signs of ischemia were seen on the EKG. TT echo showed a very large pulsatile anaechogenic area posteriorly to BVP. Transesophageal echocardiography (TEE 2D, Traditional 3D and TrueVue) highlighted a very large pseudoaneurysm of mitral-aortic interventricular fibrosa (P-MAIVF; Figures 1 and 2, long axis and short-axis views). TEE features included: 1) a very large cavity with thickened walls, extended for more than two-thirds of the prosthetic circumference and with multiple septa; 2) a large communication between the left ventricular outflow tract (LVOT) and P-MAIVF (see yellow dotted line in Fig.1A) with a to-and-fro flow into the cavity and a prominent systolic pulsation; 3) no paraprosthetic leak and absence of any attached mass or intraprosthetic aortic regurgitation. These findings suggested a prosthetic aortic valve endocarditis with an extensive periannular involvement. Moreover, the P-MAIVF may have led to “ab extrinseco” compression of the left coronary artery, with a potential role in the genesis of chest pain and ventricular arrhythmia (in absence of significant CAD at preoperative coronary angiography). An empiric antibiotic therapy with daptomycin and piperacillin-tazobactam was started. The patients subsequently underwent Bentall surgery with a subannular implantation technique (Perimount valvular prosthesis n.23 and Gelweave vascular prosthesis n.28). Figure 3 shows an intraoperative image and postoperative TEE. In conclusion, P-MAIVF is an ominous complication of prosthetic valve endocarditis. Presentation with exertional angina and cardiac arrest is unusual. TEE is sensitive for diagnosis and 3D echo provides better insights into the anatomy helping formulate an appropriate surgical strategy.