Unfortunately, this particular form of CHD is associated with structural anomalies that are rarely identified in the case of isolated atrial or ventricular septal defects, the most significant of these being a shared, or common valve that runs through the center of the heart. As such, valvular reconstruction is imperative within the context of most variants of this disease.
AVSDs: a structural overview:
There are three main components to the AVSD. The first is that of a primum ASD, which forms an illicit communication between the heart's two upper chambers, the atria. The second is that of an inlet VSD: a hole locted between the heart's two lower chambers, the ventricles. The third aspect of the AVSD involves the valves connecting the atrial chambers to the ventricular chambers. Normally, there are two of these: a valve to connect the atrial and ventricular chambers on the right side of the heart (the mitral valve), and a valve to connect these chambers on the left side of the heart (the tricuspid valve). In the heart afflicted by an AVSD, both sides of the heart share a common valve. This, combined with the "hole" in the center of the heart, results in a common atrioventricular opening, or canal.
Of course, it should be mentioned that the above constitutes a standard description of the most common form of this defect, which results from the lack of the atria and ventricles to correctly divide into separate chambers very early in the course of fetal development. More simple forms of this disease exist (consisting only of an ASD), as do more complex variations (such as when one of the ventricles is malformed, or when there is aortic obstruction).
The effects of this defect upon the body are not unlike those manifested by the VSD and the ASD. Depending upon the relative size of the communication and hence the degree of blood being leaked, a predisposition to congestive heart failure and resulting pulmonary hypertension may necessitate pharmaceutical intervention until surgical correction becomes feasible. (See last week's article for a detailed account of septal defects and their potential complications).
