A case report of surgical treatment of a dog with atrioventricular septal defect (incomplete form of endocardial cushion defect).

A 3-month-old female collie was diagnosed as having atrioventricular septal defect with ostium primum atrial septal defect (PASD). The diagnosis was made by echocardiographic observation of the PASD and goose-neck deformity on left ventriculogram. The PASD was treated surgically with a patch graft under cross-circulation cardiopulmonary bypass (CC). The PASD was identified above the ventricular septum after right atriotomy. The patch graft was sutured along the fibrous tissue of the tricuspid annulus on the ventricular side of the PASD to avoid injuring the conduction system. After the operation, cardiac function and renal output were well preserved, but the dog died 33 hr later. At postmortem examination, a mitral cleft was identified.