Abstract Body (Do not enter title and authors here): Aortic valve replacement (AVR) with biological valve prostheses (BV) avoids long-term anticoagulation compared with mechanical vale prostheses. Their durability is limited due to structural valve dysfunction (SVD). Valve degeneration is gradual, leading to bioprosthetic valve failure (BVF). We present the first case reported of acute aortic Avalus bioprosthesis SVD with severe aortic regurgitation (AR) secondary to flail leaflet.

A very active 52-year-old male with CAD, atrial fibrillation/flutter, and bicuspid aortic valve (AV) with symptomatic severe aortic stenosis treated with a 25 mm Abbott St. Jude/EPIC^TM Supra valve 16 years ago required a redo surgery for infective endocarditis with an aortic root abscess treated with a 25 mm Medtronic Avalus BV 5 years prior and aortic root reconstruction. He presented with a 3-day history of chest pain and severe dyspnea. On arrival, cardiogenic shock and respiratory failure ensued, requiring vasopressors and endotracheal intubation. CXR revealed pulmonary edema. Coronary angiogram revealed non-obstructive CAD. TEE revealed preserved LV function with severe acute AR. He underwent emergent AVR. Surgery revealed a sterile flail prosthetic valve leaflet with complete prolapse of the noncoronary cusp. A 27-mm Medtronic Evolute BV was placed. His course was complicated by transient complete heart block. He continued improving and was then discharged.

Acute AR should be suspected in patients with acute hemodynamic instability and history of AVR. TTE or TEE are crucial for the assessment of BV and diagnosis of AR. The only effective treatment for acute severe AR is emergent AVR. Newer generation BVs offer the possibly of not requiring long-term anticoagulation and enhanced durability. The PERIGON trial evaluating the Avalus bioprosthesis in AVR showed no cases of SVD with excellent durability and hemodynamic profile during the 5-year follow-up, being this the first case reported in the literature of acute catastrophic failure of this valve.

Our case highlights the importance of rapid diagnosis and intervention in acute aortic BVF. While newer BVs offer improved durability and hemodynamic properties, clinicians must remain vigilant for acute complications secondary to SVD. Studies with longer follow-up are needed to better characterize the safety and performance of the Avalus bioprosthesis. The lack of standardized definitions for SVD may have led to underreporting and underestimation of its incidence.