Rheumatoid Arthritis Presenting with Multivalvular Regurgitation, Conduction Block, and Multisite Aneurysms: A Case Report With Histologic Confirmation.

Cardiac involvement in rheumatoid arthritis (RA) is uncommon and often clinically silent, but may encompass valvular, structural, and conduction system abnormalities. Involvement of the mitral-aortic intervalvular fibrosa (MAIVF) and the membranous interventricular septum is exceptionally rare and has not been previously described in RA. A 61-year-old man with longstanding seropositive RA presented with syncope due to intermittent complete atrioventricular block. Multimodality imaging revealed severe degenerative mitral regurgitation, moderate-to-severe aortic regurgitation, a pseudoaneurysm of the MAIVF extending into the left ventricular outflow tract, and a membranous interventricular septal aneurysm. Infective and congenital etiologies were excluded by repeated negative blood cultures, 18F-FDG PET, and comprehensive imaging. The patient underwent successful surgical mitral and aortic valve replacement. Histopathological analysis demonstrated rheumatoid nodules within both excised valves, confirming immune-mediated valvular involvement. Persistent conduction abnormalities required permanent pacemaker implantation. This report describes the first documented case of a MAIVF pseudoaneurysm in a patient with RA, associated with multivalvular disease and high-grade conduction disturbance. The findings highlight the potential for severe, atypical cardiac manifestations of RA in the absence of active systemic inflammation and underscore the pivotal role of multimodality imaging and multidisciplinary evaluation in establishing diagnosis and guiding management.