Jellyfish-Like Accessory Mitral Valve Tissue Causing Near-Collapse in a Young Child.

Accessory mitral valve tissue (AMVT) causing left ventricular outflow tract obstruction (LVOTO) is rare. We report a case of AMVT causing severe LVOTO resulting in acutely progressive symptoms of near-collapse. Urgent surgical resection eliminated the patient’s life-threatening symptoms. AMVT should be considered among potential LVOTO diagnoses, and early surgical intervention may be required.