Pathology of atrioventricular valve dysplasia.

The congenital heart disease series of the Pathological Museum at La Sapienza University of Rome was revised in order to detect specimens featuring atrioventricular valve dysplasia (AVVD) in fetuses and infants. Selected for study were 67 specimens from a collection of 667 hearts: there were 36 cases of isolated tricuspid valve dysplasia (TVD), 11 cases of isolated mitral valve dysplasia (MVD), and 20 cases of combined atrioventricular valve dysplasia. All the valves were graded according to Becker's criteria, which were morphometrically validated. There is an increasing degree of dysplasia in terms of differentiation and detachment of the valve from the ventricular wall. The concept of AVVD is supported by a substantial morphologic and morphometric analogy between TVD and MVD, in spite of some peculiarities of each grade and of side-specific anomalies ("mitral arcade" on the left side and grade III dysplasia on the right one), probably attributable to differences in the embryonic development of the two valves. AVVD is sometimes associated with dysplasia of the semilunar valves, in the setting of a polyvalvular disease of possible genetic origin. More often it is combined with other defects that cause ventricular overload. In such cases, AVVD usually occurs within the overloaded cardiac section, as if it were a result of mechanical stress.