Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ Key Features +++ Essentials of Diagnosis ++ Murmur often inaudible in neonates Loud pulmonary component of S2 Common in infants with Down syndrome ECG with extreme left axis deviation +++ General Considerations ++ Results from incomplete fusion of the embryonic endocardial cushions Accounts for about 4% of all congenital heart disease Defined as partial or complete Partial AVSD There is a low insertion of the AV valves, resulting in a primum atrial septal defect (ASD) without a ventricular defect component. There are two separate AV valve orifices and usually a cleft in the left-sided valve Behaves like an isolated ASD with variable amounts of regurgitation through the cleft in the left AV valve Complete AVSD Causes large left-to-right shunts at both the ventricular and atrial levels with variable degrees of AV valve regurgitation If there is increased pulmonary vascular resistance (PVR), the shunts may be bidirectional Bidirectional shunting is more common in Down syndrome or in older children who have not undergone repair +++ Clinical Findings +++ Symptoms and Signs ++ Partial AVSD may produce symptoms similar to ostium secundum ASD Complete AVSD Failure to thrive Tachypnea Diaphoresis with feeding Recurrent bouts of pneumonia In the neonate, the murmur may be inaudible due to relatively equal systemic vascular resistance and PVR After 4–6 weeks, as PVR drops, a nonspecific systolic murmur develops S2 is loud, and a pronounced diastolic flow murmur may be heard at the apex and the lower left sternal border If a right-to-left shunt is present, cyanosis will be evident +++ Diagnosis +++ Imaging ++ Cardiac enlargement is always present in the complete form and pulmonary vascular markings are increased Often, only the right heart size may be increased in the partial form, although a severe mitral valve cleft can rarely lead to left heart enlargement as well Echocardiography Diagnostic test of choice The anatomy can be well visualized by two-dimensional echocardiography AV valve regurgitation can be detected The LV outflow tract is elongated (gooseneck appearance) +++ Diagnostic Procedures ++ Electrocardiography Extreme left axis deviation with a counterclockwise loop in the frontal plane Right, left, or combined ventricular hypertrophy is present depending on the particular defect and the presence or absence of pulmonary hypertension Cardiac catheterization and angiocardiography Cardiac catheterization is not routinely used to evaluate AVSD but may be used to assess pulmonary artery pressures and resistance in the older infant with Down syndrome Increased oxygen saturation in the RV or the right atrium identifies the level of the shunt Angiocardiography reveals the characteristic gooseneck deformity of the LV outflow tract in complete AVSD +++ Treatment ++ Spontaneous closure does not occur Surgery is required Complete correction in the first year of life, prior to ... Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth