title: Supernumerary mitral valve producing subaortic stenosis.
abstract: A ten-year-old girl with severe subaortic stenosis was found to have relatively mature valvular endocardial cushion tissue (fibromyxomatous sheets with a chorda tendinea attached to a left ventricular papillary muscle) immediately beneath the aortic valve. This structure behaved like a valve mechanism, obstructing the left ventricular outflow tract during ventricular systole. This anomaly is an extreme on the spectrum of obstructive endocardial cushion malformations.
mesh_terms: D001020:Aortic Stenosis, Subvalvular / Q000151:congenital* / Q000209:etiology / Q000473:pathology / Q000601:surgery; D002312:Cardiomyopathy, Hypertrophic / Q000151:congenital*; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications / Q000473:pathology / Q000601:surgery; D006801:Humans; D007223:Infant; D008943:Mitral Valve / Q000002:abnormalities* / Q000601:surgery