Left Atrial Myxoma Presenting with Severe Mitral Regurgitation Requiring Mechanical Mitral Valve Replacement and Lifelong Anticoagulation: A Case Report

Background: Left atrial myxoma is the most common primary cardiac tumor, often presenting with diverse clinical manifestations including obstructive, embolic, and constitutional symptoms. Although benign, its potential to interfere with intracardiac hemodynamics can lead to significant complications. The coexistence of atrial myxoma with severe mitral regurgitation (MR) is uncommon and may complicate both diagnosis and management. Case Presentation: We report the case of a 45-year-old female who presented with progressive exertional dyspnea, reduced exercise tolerance, and intermittent chest discomfort. Transthoracic echocardiography revealed a large, mobile left atrial mass prolapsing through the mitral valve during diastole, along with mitral annular dilatation and anterior leaflet prolapse. Cardiac magnetic resonance imaging confirmed a heterogeneous mass measuring 9.5 × 3.5 cm arising from the interatrial septum. The patient underwent urgent surgical excision of the mass. Intraoperative findings demonstrated significant structural degeneration of the mitral valve, rendering it non-repairable and necessitating mechanical mitral valve replacement. Results: Postoperative transesophageal echocardiography confirmed complete tumor removal and normal function of the mechanical prosthetic valve. The patient had an uneventful recovery with resolution of symptoms. Anticoagulation therapy with warfarin was initiated due to the mechanical valve, with a target international normalized ratio (INR) of 2.5–3.5 (5). During the initial 3-month follow-up, the patient’s time in therapeutic range (TTR) was approximately 52%, with gradual improvement in INR control and no reported thromboembolic or bleeding complications. Conclusion: This case highlights a rare presentation of left atrial myxoma associated with severe mitral regurgitation requiring valve replacement. While tumor–valve interaction may have contributed to valvular dysfunction, a definitive causal relationship cannot be established. Lifelong anticoagulation in this patient was indicated solely due to mechanical valve implantation rather than the presence of myxoma. Early diagnosis and timely surgical management remain essential for optimal outcomes.