FIG 34.7 Long-axis section through the left ventricle showing the parasternal echocardiographic view and illustrating the components of the mitral valvar complex All components work in harmony when the valve is normal The specimen was prepared subsequent to injection of fixative under pressure in the left ventricle, maintaining the systolic configuration of the leaflets Classification The anomalies affecting the morphologic mitral valve in pediatric patients should be classified according to morphology and function Both classifications are important for diagnosis and treatment and must be presented and understood Dysplastic mitral morphologies can be encountered in either a predominant regurgitation, a stenosis, or both physiologies, and either physiology can be present in any type of dysplastic valve Therefore the abnormal mitral valve should be presented according to both its morphologic and functional classifications As shown in the discussion of the embryology of the mitral valve earlier in this chapter, the formation of the mitral valve leaflets, the suspension apparatus, and the papillary muscles originate from the same continuous mechanism and cannot be separated into each of the three levels (valve, cords, papillary muscle) Hereafter, therefore, the anomalies of the mitral valve are presented according to their morphology, with abnormal morphology (dysplastic valves) presented first and the normal morphology last Echocardiographic studies of congenital mitral valve disorders now tend to be done systematically level after level (annulus, leaflet, chordae, and papillary muscle).3 This approach leads to a final diagnosis from the morphologic and physiologic points of view, as presented here, and is used by most.4 Dysplastic Valves The three main pathologic subgroups usually described are more benchmarks on a continuous spectrum than totally separated groups Papillary Muscle to Commissure Fusion, Arcade or Hammock Mitral Valve Papillary muscle to commissure fusion is the most common feature found in dysplastic mitral valves Rarely isolated, it is most often associated with either of the two following lesions Again, a large spectrum of lesions can be seen with short and thin but present cords on one end and totally absent cords with large, bulky, and obstructive papillary muscle on the other end In the most severe form, the muscles come together on the leading edge of the aortic leaflet, forming the muscular arcade5 observed by the pathologist (Figs 34.8 and 34.9) FIG 34.8 Rare example of pure papillary muscle–to-commissure fusion with a thin leaflet The two papillary muscles are evenly developed and spaced Chordae on the inferoseptal papillary muscle are very short and absent on the superolateral one Accessory papillary muscles dedicated to the posterior leaflet are present FIG 34.9 Papillary muscles supporting the leaflets fuse along the leading edge of the aortic leaflet, producing a muscular arcade (left) Note also the obliteration of the interchordal spaces, which would have rendered the valve stenotic (arrow) (Right, From Séguéla P-E, Houyel L, Acar P Congenital malformations of the mitral valve Arch Cardiovasc Dis 2011;104[8–9]:465–479.) When viewed from the atrial aspect, with the valve intact as seen by the surgeon, the intermixing of cords attached to the enlarged papillary muscle gives the appearance of a hammock.6 The abnormal attachments produce mitral valvar insufficiency, but the morphologic appearance suggests that the valve would also be stenotic Parachute Mitral Valve Anomalies of the papillary muscles produce the lesion most usually described as the “parachute” lesion.7–9 In this regard, it should be remembered that, although usually described as being “anteromedial” and “posterolateral,” the papillary muscles of the mitral valve are located inferoseptally and superolaterally when viewed with the heart in an attitudinally appropriate position (see Chapter 2) A