Retained anterior mitral leaflet mimicking mass after chordal-sparing mitral valve replacement

A woman in her thirties with severe eccentric mitral regurgitation and reduced left ventricular ejection fraction (LVEF 30-35%) underwent chordal-sparing mechanical mitral valve replacement (MVR) via a transseptal approach. Post-operative echocardiography revealed an echogenic mass near the mitral prosthesis, raising suspicion of a retained anterior mitral leaflet (AML) or ruptured sub-valvular structure. Due to persistent imaging concerns, she underwent a redo sternotomy and transaortic excision of the retained AML with subvalvular apparatus. Post-second surgery, the patient recovered well with improved LVEF and normal prosthetic valve function. This case highlights the rare complication of retained leaflet tissue following chordal-sparing MVR and the importance of early recognition and intervention.