congenital abnormality of the mitral valve characterized by the presence of a single papillary muscle from which the tendinous cords (chordae tendinae) of both valve leaflets divide; thus the resemblance to a parachute; the condition often produces a stenosis as the combined result of the tugging action of the cords on, and the subsequent narrowing between, the leaflets. SYN: parachute deformity.