parachute mitral valve exceptionally corresponds to the two muscles fused to produce a solitary myocardial mass (Fig 34.10, right) Commonly, a predominant papillary muscle—usually the anteromedial (or inferoseptal)—is sided with a diminutive posterolateral (or superolateral) papillary muscle The latter can be connected to a patent commissure or to the undersurface of an imperforated commissure The functional lesion of a parachute mitral valve can be either regurgitating or stenotic according to the size of the orifice and to the mobility of the leaflets and suspension apparatus combination It is very often associated with papillary-muscle-to-commissure fusion FIG 34.10 Two lesions described as producing the so-called parachute mitral valve Left, Absence of the superolateral papillary muscle, so that all the tendinous cords converge on the inferoseptal muscle Right, Abnormal mitral valve that was removed at surgery The papillary muscles are fused and the tendinous cords are thickened Mitral Cleft The cleft mitral valve is often isolated and can be easily differentiated from a left atrioventricular valve in a partial atrioventricular septal defect It is an actual cleft with no suspension apparatus on the edges of the defect The cleft is centered on the aortic commissure between the noncoronary and left coronary cusps Each half of the anterior leaflet at the midportion bears the attachment of the strut chordae, whereas the papillary muscles have a normal appearance and function This is well explained on the basis of failure of fusion between the left ventricular components of the superior and inferior atrioventricular cushions,10 but in the setting of separate right and left atrioventricular junctions (see later),11,12 the space between the cleft components of the leaflet creates the substrate for valvar incompetence With time, the cleft mitral valve's regurgitation will generate secondary lesions at the edges of the cleft, such as thickening, rolling in, and retraction The defect is never stenotic and may generate no or only little regurgitation for a long time (Fig 34.11) FIG 34.11 These images show congenital clefts in the aortic leaflet of the mitral valve (A) Heart with an intact ventricular septum Note that both parts of the cleft leaflet are dysplastic and there is thickening of the tendinous cords (B) Heart with an associated perimembranous ventricular septum defect The cleft is supported by tendinous cords that attach to the crest of the deficient muscular ventricular septum, but the cleft is directed toward the aortic root (arrow) A very rare cleft of the posterior leaflet can be found Morphologically it could be defined as a cleft of the posterior leaflet or hypoplasia or aplasia of the middle scallop Dual-Orifice Mitral Valves Mitral valves with dual orifices are very rare as opposed to dual orifices found in the left atrioventricular valves of complete or partial atrioventricular septal defects The two orifices are produced by the presence of a tongue of valvar tissue, which joins together the facing edges of the mural and aortic leaflets, with each orifice supported by one of the papillary muscles (Fig 34.12) FIG 34.12 Tongue of valvar tissue joining together the aortic and mural leaflets of the mitral valve, producing dual valvar orifices (stars) Note that each orifice is supported by one of the paired papillary muscles of the valve Accessory Mitral Valve Tissue The intercordal spaces are filled with a dense network of immature valve tissue (Fig 34.13) When there is continuity between the anterior and posterior leaflets, the accessory valvar tissue may generate a gradient directly related to the size of the perforations in the accessory tissue.13 When the accessory valve tissue is