Congenital cyanotic heart disease 2
Complete AV Canal Defect (AV Septal Defect, Endocardial Cushion Defect)
Complete AV canal defect occurs when the “central" heart fails to develop.
The resulting large hole communicates between the atria and ventricles, and the defect also creates a failure of septation of the mitral and tricuspid valve.
The anterior and posterior segments of each leaflet join each other through the defect (normally, they are separated), resulting in a common AV valve.
The AV valve abnormatiry can cause a significant left- and right-side AV valve regurgitation.
In addition, there is left-to-right flow across the atrial and ventricular septal defects.
The overall result is alarge left-to-right shunt and valve regurgitation, leading to a cardiac volume overload and HF.
This is all due to a defect in the development of the endocardial cushions.
This is the most common heart defect in Down syndrome (trisomy 21).
About 30:40% of children with down syndrome who have congenital heart disease will have AVSD.
About 70% of endocardial cusion desfects is associated with down syndrome.
The child can present with the murmur of a VSD, as well as a middiastolic rumble that is due to increased pulmonary venous retum and increased diastolic flow across the AV valve.
An apical pansystolic murmur of AV valve regurgitation occurs if there is regurgitation through the mitral portion of the AV valve.
These infants most often present with heart failure by 2 months of age.
Symptoms can start in early infancy, if there is a large left ventricle- to-right atrial shunt or if there is significant valvular dysfunction.
ECG usually shows severe LAD (northwest axis) and prominent voltage with biventricular hypertrophy.
CXR reveal non spesfic generalized cardiomegaly with increased pulmonary blood flow.
Echo is diagnostic
Medical management of HF can be helpful, but early surgery is necessary within the first 6 :12 months to prevent pulmonary vascular disease ( Eisenmenger syndrome).
Usually, the best outcomes occur in those with “balanced” defects and similar-size ventricles.
Occasionally, 1 ventricle can be small/hypoplastic.
Potenial post-operative complications :-
Damage to AV node conduction fibers.
Av valve dysfunction.
Children with Down syndrome traditionally have a good chance of having compatible anatomy for correction, but they do require surgical correction early (i.e., before 6 months of age) in order to avoid irreversible pulmonary vascular disease.