Atrioventricular septal defect pathophysiology

Pathophysiology
There are many underlying mechanisms resulting in atrioventricular septal defect depends largely on the nature of interaction of blood flow between the right and left sides of the heart. Factors influencing the severity include: ventricular imbalance, the size of AV septal defects, AVV competence, the degree of right-sided or left-sided outflow obstruction, pulmonary vascular resistance, the amount of atrioventricular valve regurgitation and the magnitude of blood flow through the ventricular septum. The determination of the degree of left-to-right shunting can be done examining the size of the communication and the relative compliance of the two atria and ventricles.

Newborns may experience little left-to-right shunting as a result of a less compliant right ventricle and a relatively high PVR. Larger defects may result in mixing of a common or near-common atrium and create components of right-to-left shunting. The propensity for left-to-right shunting increaes with age as a result of a decrease in PVR and right ventricle compliance increase.

Asymptomatic patients often have little atrioventricular valve regurgitation and higher pulmonary vascular resistance. Pulmonary overcirculation is often an earmark of an AVSD.

Infants may present with congestive heart failure, tachypnea, excessive sweating, failure to thrive, extremis with acidosis, severe hypoplasia of left-sided structures with ductal-dependent systemic circulation, and severe cyanosis in right-sided structures with ductal-dependent systemic circulation. If an AVSD is coupled with an VSD, there is a high risk of pulmonary vascular disease.

Older patients may present progressive right ventricle enlargement and pulmonary vascular engorgement.The degree of regurgitation through the anterior mitral valve leaflet cleft can result in a left ventricular outflow tract obstruction of a coarctation of the aorta.