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Perimembranous Ventricular Septal Defects



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Perimembranous defects (also known as 'conoventricular') are the most common type of VSD. The defects vary in size and occur beneath the aortic valve on the left side of the septum, extending to the right under the septal leaflet of the tricuspid valve. The defects may be associated with formation of aneurysm tissue along the right ventricular side of the septum. It is thought that this results from the apposition of the septal leaflet of the tricuspid valve against the VSD. Over time, progressive development of this aneurysm tissue may be responsible for spontaneous closure of some perimembranous septal defects.

Perimembranous septal defects may be associated with malalignment of the great arteries and ventricles. If malaligned, two clinical consequences may occur. First, there will be emptying of both ventricles into the overriding great artery. Secondly, there is an increased likelihood of ventricular outflow obstruction. With anterior malalignment, the right ventricular outflow may be dynamically obstructed, and with posterior malalignment, the left ventricular outflow may be obstructed.


Spontaneous closure...


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