Explain Fossn Ovalis Defect (Ostium Secundum Defect) ?
This is the most common type of atrial septal defect.
The usual approach is through a midline incision and median sternotomy. In young girls, for cosmetic reason, approach through a submammary light thoracotorny or low and minimally invasive midline incision is used. Piece or pericardium is harvested for patch closure of the defect. Ascending aortic and bicaval cannulations are done for cardio pulmonary bypass. The operation is done at 32 to 34°C after aorta is clamped aortic root cardioplegia given.
After snaring SVC and IVC tapes, right atrium is opened parallel to atrioventricular groove. Anatomy of the defect is studied and mitral valve is inspected and tested for incompetence. When the defect is fenestrated, these strands are excised to form a single large defect. Small defects can be directly closed but a patch closure is generally preferred. The pericardial patch is first sutured to the inferior aspect of the defect between inferior vcna cava and left atrium. Great care is taken not to confuse the Eustachian valvc of' IVC with remnant qf the floor of fossa ovalis. Such an error can lead to diversion of IVC to left atrium when the operation is done under circulatory arrest without an IVC cannula. Once the lower part of the patch is anchored, the rest of the patch is sutured to the margins of the defect. Care is taken to avoid injury to the atrio ventricular node situated at the apex of the Koch's triangle.