Cardiopulmonary bypass with bicaval cannulation is used. After aortic cross-clamping and cardioplegia delivery, a transverse right ventriculotomy is made just superior to the suspected obstructing muscle band (Fig. 23-1). This can be identified by an overlying enlarged coronary branch, external palpation of the right ventricle for a prominent ridge, or careful pressure measurements before beginning cardiopulmonary bypass. By retracting the inferior margin of the ventriculotomy, a circular opening can be seen, often covered with fibrous tissue. This obstruction is incised anteriorly initially. After identifying the papillary muscles of the tricuspid valve, the remainder of the obstructing muscle is resected. The accompanying ventricular septal defect should now be apparent. This ventricular septal defect may be closed through the right ventriculotomy or through a separate right atrial incision, working through the tricuspid valve (see Chapter 21). The right ventriculotomy is then closed with a running 5-0 Prolene suture.

Several centers have reported satisfactory results with complete repair of tetralogy of Fallot in neonates. However, as
the long-term results of repair of tetralogy of Fallot become available, the significant problem of right ventricular failure and its causes are being elucidated. It is now believed that pulmonary regurgitation plays a major role in the development of right ventricular dysfunction. For this reason, some surgeons advocate a staged approach in patients who require surgery before 4 to 6 months of age. Patients who become symptomatic early in life or are ductal dependent tend to have small pulmonic valves and usually require a transannular patch. By performing an initial shunt procedure (see Chapter 18) and delaying definitive repair until the patient weighs at least 6 kg, the hope is that the native valve and/or annulus can be preserved.

In addition, 3% to 5% of patients with tetralogy of Fallot have an anomalous left anterior descending coronary artery arising from the right coronary artery. The course of the left anterior descending coronary artery across the right ventricular outflow tract may preclude an appropriate ventriculotomy to relieve the obstruction. If these patients need surgery in the first few months of life, a shunt procedure is preferred. Some of these patients may be able to undergo a transatrial repair that is best performed in patients weighing at least 5 kg. However, many will require a right ventricular to pulmonary artery conduit as part of their repair, and this is best delayed until 12 to 18 months of age.

A median sternotomy provides excellent exposure. A generous patch of autologous pericardium is harvested, attached with metal clips to a piece of plastic, placed in 0.6% glutaraldehyde solution for 6 to 8 minutes, and then rinsed in saline. Such treatment fixes the pericardium and thereby lessens the chances of aneurysmal dilation of the patch. If the patient has undergone a previous systemic to pulmonary shunt, it is dissected circumferentially to allow for closure with a metal clip at the initiation of cardiopulmonary bypass (see Chapter 18). In the absence of a shunt, minimal manipulation should be performed before cannulation to prevent hypoxic spells.

Besides confirming the anatomy with transesophageal echocardiography, an external examination of the heart is conducted. The surgeon looks for an anomalous coronary artery crossing the right ventricular outflow area, evaluates the size of the main and branch pulmonary arteries, and notes the distance between the aortic valve and the left anterior descending artery, which indicates the width of the right ventricular outflow tract. These observations help determine the surgical approach. A hypoplastic right ventricular outflow tract indicates the need for a right ventriculotomy and the probability of a transannular patch.

Standard bicaval and aortic cannulation is used to initiate cardiopulmonary bypass. A vent is placed through the right superior pulmonary vein into the left ventricle. Systemic cooling to 28°C to 32°C is achieved, the aorta is clamped, and cold blood cardioplegic solution is infused into the aortic root (see Chapter 3). In patients with discrete infundibular muscular obstruction and an adequate pulmonary annulus, the repair can be done through a transatrial approach.

After achieving cardioplegic arrest, the tapes around the venae cavae are snugged down, and an oblique right atriotomy is made. The septal leaflet of the tricuspid valve is retracted to allow exposure of the ventricular septal defect and the right ventricular outflow tract. A cardiotomy sucker is placed in the infundibular ostium and dissecting scissors are used to resect muscle and fibrous tissue circumferentially. A right angle clamp is then used to identify hypertrophied muscle bands. With the clamp in place, each muscle band is divided with a no. 15 knife blade, cutting the band until the clamp is reached. The cut edge of the band can then be grasped with a forceps and resected with sharp scissors. When adequate resection of hypertrophied muscle has been completed, it should be possible to visualize the pulmonic valve (Fig. 23-2). A valvotomy can be performed by everting the leaflets and incising the commissures, if necessary. The annulus is sized with a Hegar dilator to ensure an adequate valve opening for the patient’s size (see Appendix section).

Some surgeons prefer a right ventriculotomy approach for patients with tetralogy of Fallot. The advantages include the ability to resect all obstructing muscle bundles under direct vision and to enlarge an underdeveloped infundibulum with a patch. The potential disadvantages include scarring of the right ventricle, which may give rise to ventricular dysfunction and dysrrhythmias. Even when
a transventricular approach is used, every attempt is made to preserve the pulmonic valve leaflets and to avoid a transannular patch.

A vertical right ventriculotomy is made, and the edges are retracted with pledgeted sutures. The hypertrophied infundibular muscle bundles are incised and selectively excised as needed to open up the outflow tract (Fig. 23-3). The large malalignment type of ventricular septal defect can now be seen and is closed with a Dacron velour patch using a continuous suture of 5-0 Prolene. With this technique, traction on the patch by the assistant facilitates placement of the next stitch. Suturing begins at the 1 o’clock position and continues clockwise around the tricuspid annulus taking shallow bites of thickened endocardium up to the aortic annulus where the suture is tagged at the 8 o’clock position (Fig. 23-4). The other needle is then used to complete the suture line.

Whether a transatrial or transventricular approach is used, evaluation of the pulmonic valve may be difficult working from below. In these cases, a separate vertical incision is made on the main pulmonary artery. Many surgeons prefer to use a transpulmonary approach to the pulmonic valve in all patients. After inspecting the valve and completing a valvotomy, if required, a Hegar dilator of the appropriate size is passed into the right ventricle (see Appendix section). If the annulus cannot be opened adequately with passage of sequentially larger dilators, the incision on the pulmonary artery is extended across the annulus only as far as necessary. This incision should be made through the anterior commissure of the pulmonic valve to reduce the amount of pulmonary insufficiency.