What is Intracardiac Repair of Tetralogy of Fallot ?
Technique : The essential steps are: (I) relief of right ventricular outflow obstruction, and (2) closure of ventricular septal defect directing LV to aorta without residual shunt and without producing art block. The anatomy should be well delineated by echocardiography and at times angiography pre-operatively.
After median sternotomy, the external anatomy is studied carefully. This includes the annulus, main pulmonary artery and light and left branches. Abnormality of the course of the coronary arteries is also studied.
The heart is approached through mediam sternotomy. Pericardium is harvested and if it is decided to use gluteraldehyde treated pericardium it is placed in that solution. Aorta is dissected and separated from the main pulmonary artery. If a transannular patch has to be extended up to the hilum of the lung the pulmonary artery is dissected up to that point. A functioning shunt or ductus is dissected and looped and got ready for ligation on cardiopulmonary bypass. Ascending aorlic and direct cannulation of superior and inferior vena cavae are done. Patient is cooled down lo 28". After clamping the aorta and giving cold blood cardioplegia into aorta, caval tapes are snared. Right atrium is opened vertically parallel to the alrioventricular groove. A lelt atrial vent is passed either through a patent foramen ovale or by incising the atrial septum. Repair cans be done by transatrial approach. In some cases a pulmonary arleriotomy has to be combined with bansatrial approach. When n trans annular patch is required, pulmonary arteriotomy is extended across the annulus to the right ventricular outflow.
Intracardiac repair could also be done through a right ventriculotomy. It is less commonly used these days. In transition approach the tricuspid valve is retracted and infundibular resection is done and obstruction removed up to the pulmonary valve. Pulmonary valvotonly is done either through this approach or after making a vertical pulmonary asteriotomy. The fused commissars of the valve are divided up to the wall of the artery. Appropriate sized Hegar's dilators are passed to decide the necessity for a transannular patch.
The ventricular septal defect is then closed with Dacron or Goretex patches. The patch is cut slightly bigger than the defect. VSD can be closed with continuous or interrupted pledgetted sutures using 5-0 or 4-0 prolene. Care is taken not to injure conduction bundle, which courses through the postero-inferior margin of venixicular septal defect. The undivided bundle runs on the left ventricular aspect just below the crest of muscular septum. After closure of VSD attention is turned to the RV outflow. Diameter of right and left pulmonary arteries are measured with Hegar's dilators and decision made regarding the extent of patch to be used.
When a transannular patch is used it is sutured to the RV outflow extending to the main and branch pulnlonary artery. At this stage patient is rewarmed, left atrial vent removed and incision in the atrial septum is closed. De-airing of chambers of the heart is carried out and aortic clump removed. Right atriotomy is closed with 5-0 psolene.
A patent foramen ovale, which is present, is always closed in older babies and children. In neonates and infants it may be left open to allow decompression by right to left shunting. Acute light atrial hypertension caused by right ventricular failure is thus avoided. The size of the defect left should be 3 to 4 mm.