Definition
The AVSD is a malformation that affects both the septum and the valve level between the atria and ventricles (endocardial cushion defect). It consists of a primary atrial septal defect and a common atrioventricular valve (no separate tricuspid and mitral valve) that overrides a ventricular septal defect of varying size.
Indication and Timing
The closure of hemodynamically relevant septal defects is indicated in order to prevent possible complications (heart failure, lung flooding and, in the mid-term, pulmonary hypertension?. Generally infants with these defects develop symptoms at the age of 3-6 months. The main symptoms are feeding problems, failure to thrive and frequent pulmonary infections. The symptoms are similar to those caused by a large VSD. If heart failure persists despite anticongestive treatment, a corrective operation can be performed even before the third month of life. With pressure division VSDs, the timing of the operation depends on signs of right heart strain and the development of AV valve insufficiency. The smaller the VSD part of the defect, the later symptoms may occur. If the VSD portion is closed and the ASD part small, the operation can be postponed beyond the infant period depending on the AV dysfunction and symptoms.
Operation
When the VSD part is large, double patch closure of the VSD and the ASD parts is usually performed. A patch is cut to the correct size and fixed below the bridging leaflets. Next the ASD is closed by attaching a second pericardial patch to the VSD patch, suturing through the bridging leaflets. Before closure, the cleft in the left-sided AV valve is closed with single button sutures. Reconstruction of the right-sided AV valve may also be necessary. In the case of a small VSD portion this can also be closed by direct suturing. Closure of the cleft in the left-sided AV valve and of the ASD is done using the double-patch technique described above. In this heart defect the AV node is displaced downwards. The His bundle runs along the posterior VSD rim and the potential danger of damage must be taken into consideration. If AV block is present postoperatively the implantation of a permanent pacemaker may be necessary.
