Atrioventricular canal malformation is a congenital disorder formed by underdevelopment or overabsorption of the interatrial septum of the primary foramen during embryonic development. It can be divided into two types: partial atrioventricular canal malformation and complete atrioventricular canal malformation, with high left-to-right shunt flow at the atrial level, early onset of symptoms and more severe disease. The pathophysiological changes produced by AV canal malformations are mainly left-to-right shunts of varying degrees. The magnitude of shunt flow depends on the lesion. In cases with an intact ventricular septum and no atrioventricular valve insufficiency, the left-to-right shunt is present only at the atrial level, resulting in circulatory physiological effects, mainly volume overload of the right ventricle, increased right ventricular beat volume and pulmonary circulation blood flow, similar to foramen ovale type 2 septal defect; in cases with left atrioventricular valve insufficiency, the left ventricular blood flows back into the left atrium during cardiac contraction, resulting in a significant increase in left-to-right shunt flow and an increase in both left and right ventricular beat volumes, The left to right fractional flow increases significantly, and both left and right ventricular volumes increase. In these cases, significant cardiac enlargement and heart failure can occur in early life. In cases with complete atrioventricular coaptation, the left atrial blood flows into the right ventricle during diastole and the left ventricular blood flows into the right atrium during systole because of the large defect in the ventricular septum, and the left-to-right fractional flow is greater. In late cases, as pulmonary vascular resistance rises, left-to-right shunt flow gradually decreases, eventually presenting right-to-left reverse shunt.