accessory mitral valve

Clinical History:A 30-year-old asymptomatic female is referred for transthoracic imaging as part of an evaluation of a family history of sudden cardiac death. Her examination is benign, she has no murmurs. The electrocardiogram is normal. Her ultrasound images are shown below.

A parasternal long axis image in mid-diastole demonstrating the left atrium (LA), left ventricle (LV) and a serpiginous membrane between the anterior and posterior mitral valve leaflet (arrows). Color flow examination and pulsed Doppler examination (not shown) failed to demonstrate either significant mitral regurgitation or stenosis