Rare Incidental Finding of an Interventricular Membranous Septal Aneurysm in an Adult Presenting for Aortic Valve Replacement.

Interventricular membranous septal aneurysm (IVMSA) is a rare cardiac anomaly that typically coexists with other cardiac malformations. Recognition of IVMSAs is important for risk mitigation of potentially serious complications such as right ventricular outflow obstruction and proper characterization of the lesion is critical for planning of surgical repair. Literature reports of this condition are sparse and appear limited to case reports. Bicuspid aortic valve (BAV) is a common congenital cardiac malformation tending to present later in life with symptomatic stenosis and is frequently associated with other defects. We report an unusual case of an elderly woman with a BAV undergoing aortic valve replacement who was incidentally diagnosed with an IVMSA. This case report describes intraoperative transesophageal echocardiogram (TEE) characterization of the IVMSA used to help plan the surgical procedure. TEE accurately visualized the IVMSA's exact anatomic location and impact on cardiac function which led to the decision to surgically repair the IVMSA with an autologous patch. This report also includes a comparative discussion of clinical presentations, diagnostic approaches, and management strategies in previously published IVMSA case reports and considerations for operative management.