Severe Mitral Stenosis and Regurgitation Due to Bioprosthetic Valve Failure with Massive Pannus

INTRODUCTION: Bioprosthetic valve failure after mitral valve replacement is a well-recognized phenomenon, with pannus overgrowth being one notable cause. The standard treatments include redo surgical mitral valve replacement and the less invasive transcatheter treatment, mitral valve-in-valve. However, the feasibility and safety of performing mitral valve-in-valve when pannus overgrowth has reduced the valvular opening to a mere pinhole remains uncertain. CASE PRESENTATION: A 76-year-old woman, who had previously undergone mitral valve replacement, was admitted for congestive heart failure. Severe mitral stenosis and severe mitral regurgitation were diagnosed using transthoracic echocardiography. During redo mitral valve replacement, we observed that the prosthetic valve leaflets on the left atrial side were almost entirely covered with pannus tissue, leaving only a central pinhole for blood flow. Macroscopic and microscopic examination of the bioprosthesis revealed accordion-like leaflet deformation on the ventricular side. CONCLUSIONS: Although the transcatheter valve-in-valve procedure is recognized as a less invasive treatment option for degenerated biological valves, in certain cases such as ours, open surgery becomes imperative as the most appropriate treatment.