[Linear insertion of the atrioventricular valves without defect].

On a first anatomical series of 52 hearts of trisomic 21 fetuses, published in June 2002, we described a new minor cardiac anomaly, belonging to the atrioventricular septal defect, with a linear insertion of the atrioventricular valves without defect. We want to confirm these data, on a larger series of 213 new hearts of trisomic 21 fetuses by adding a complementary section to the standard examination; 100% of controls have shown a normal insertion with an offsetting of the atrioventricular valves. On 113 out of these 213 hearts of trisomic 21 fetuses, with a so called "normal" heart at the standard examination showing no defect, the complementary section has shown that only 37.2% of these hearts have a normal insertion, whereas 62.83% show a linear insertion, without offsetting and without any septal defect. This linear insertion has been observed in all the different types of atrioventricular septal defect as a good hallmark for trisomy 21; but, since then, they have always been described associated with a septal defect, atrial or ventricular. Our hypothesis is that the linear insertion of the atrioventricular valves without defect is the minor form of the atrioventricular septal defect spectrum, taking place between the prior described partial types of atrioventricular septal defect, in which there is always a defect (ostium primum type atrial septal defect or inflow type ventricular septal defect), and the real normal heart. A precise description of the level of the complementary section and of the anatomic peculiarities of the linear insertion of the atrioventricular valves without defect would help its screening in fetal ultrasonography.