Minimally Invasive Surgical Resection of Accessory Mitral Valve Tissue Causing Severe Symptomatic Left Ventricular Outflow Tract Obstruction in an Adult

Abstract

Objective: We report a rare case of adult onset, symptomatic, severe left ventricular outflow tract obstruction secondary to accessory mitral valve tissue that was treated surgically through a minimally invasive partial sternotomy approach. Methods: A 29-year-old female with a previous diagnosis of a sub-aortic membrane with 6 months of progressive chest pain, fatigue, palpitations, and presyncope presented to the emergency department with acute onset of severe chest pain, left arm numbness, palpitations, and light-headedness. Transthoracic and subsequent transesophageal echocardiogram demonstrated a mobile, parachute-like mass in the left ventricular outflow track with severe outflow obstruction (resting velocity 3.9m/s and peak gradient 60mmHg). The patient was transferred to our institution for surgical evaluation. Results: Review of the echocardiographic imaging demonstrated obstructing accessory mitral valve tissue (Figure A). The patient underwent surgical resection of the obstructing mass through a partial upper-sternotomy. Accessory mitral valve tissue attached to the aorto-mitral curtain was removed en bloc with chordal attachments to the posteromedial papillary muscle and muscular interventricular septum (Figure C and D). A small, hemodynamically insignificant sub-aortic membrane was also excised. There was no residual gradient, and valvular and ventricular functions were preserved (Figure B). The patient was discharged home on postoperative day 3. Conclusions: While accessory mitral valve tissue rarely presents in adulthood it should remain part of the differential diagnosis of symptomatic left ventricular outflow tract obstruction. Early surgical intervention is recommended and may be performed safely via less invasive surgical approaches. Figure. Accessory mitral valve tissue causing symptomatic, severe left ventricular outflow tract obstruction before (A) and after (B) surgical resection though a minimally invasive partial sternotomy. (C) Surgeon’s view of the left ventricular outflow tract through the aortic valve of the accessory mitral valve tissue, with severed chordae tendinae, attached to the aorto-mitral curtain beneath the left/non-coronary commissure of the aortic valve. (D) Resected accessory mitral valve tissue