ABSTRACT
Atrioventricular septal defect is a complex congenital heart disease in which cardiac septation is deficient especially at atrioventricular and ventricular levels. The anatomopathologic experience at the National Institute of Cardiology [quot ]Ignacio Chávez[quot ] is described; an anatomo-embryological correlation was made to gain an insight of the pathogenesis. Seventy hearts were analyzed morphologically with the sequential segmentary system. Atrial situs, connections of cardiac segments, cardiac septa, septal defects, ventricular geometry, fibrous skeleton and associated anomalies were determined. Histologic sections of chick embryonic hearts were analyzed and compared with stages of human heart development, serving as basis to elaborate the anatomo-embryological correlation. Seventy hearts had a common atrioventricular valve and five had two separated atrioventricular valves. The ventricular septal defect was open in the first type and closed in the second; the other features were the same in both. This cardiopathy is shown as a broad spectrum of anatomical variations. The morphological knowledge of this cardiac malformation is useful to understand the physiopathology, to make a precise clinical diagnosis, and to give the best orientation to the surgeon. Delay in the development of the atrioventricular cushions is emphasized as the pathogenetic explanation for this type of congenital heart disease.