Left Ventricular Outflow Tract Obstruction Due to Accessory Mitral Valve Tissue: An Unusual Systolic Murmur in an Elderly Patient.

backgroundAccessory mitral valve tissue (AMVT) is a rare congenital anomaly that is typically diagnosed during childhood and overlooked in elderly patients presenting with left ventricular outflow tract (LVOT) obstruction. CASE SUMMARY: A 73-year-old man presented with exertional presyncope and a systolic murmur. Transthoracic echocardiography revealed a mobile sac-like structure protruding into the LVOT, causing a 74 mm Hg gradient despite a normal aortic valve. Multimodal imaging confirmed a type IIB2 AMVT with dynamic prolapse. Surgical resection and histological analysis confirmed valve-like tissues. At the 3-year follow-up, the patient had remained asymptomatic with no recurrence. DISCUSSION: This case shows that AMVT, although congenital, can rarely present in elderly individuals. A crescendo systolic murmur with beat-to-beat variability aids diagnosis. Multimodal imaging is critical for diagnosis and surgical planning. Prompt excision and careful perioperative management ensure durable relief and favorable long-term outcomes. TAKE-HOME MESSAGES: AMVT, although congenital, can present as LVOT obstruction, even in elderly patients. A crescendo systolic murmur with beat-to-beat variability is a clinical sign of dynamic obstruction caused by AMVT.