Double Switch for CC-TGA with Technical Modifications

The patient is a twelve-month-old boy born at full term with a prenatal diagnosis of corrected transposition and intact ventricular septum with mild displacement of the tricuspid valve. He was admitted to the NICU for observation for three days, but developed progressive heart failure with severe right ventricular (RV) dysfunction and moderate to severe tricuspid regurgitation (TR). He subsequently underwent pulmonary artery (PA) banding at seven weeks. After banding, there was an improvement in RV function and he was feeding well with good weight gain. However, the patient developed intermittent Mobitz type I second degree heart block. Cardiac catheterization at eight months demonstrated supra-systemic left ventricular (LV) pressures and a transthoracic echocardiogram (TTE) at nine months demonstrated mild RV systolic dysfunction, mild TR, normal LV systolic dysfunction and a peak gradient of 100 mmHg across the PA band. He was thus referred for surgical intervention.

The Surgery

Procedures performed included a double switch operation comprised of an arterial and atrial switch using the modified Senning approach, supra-AS patch repair with a large coronary button and two-patch sinus enlargements, PA band takedown, branch PA plasty, and dual chamber pacemaker insertion for pre-existing high grade heart block.

Preoperative transesophageal echocardiogram (TEE) demonstrated standard corrected transposition anatomy with ventriculoarterial and atrioventricular discordance. Mild apical displacement of the tricuspid valve was also seen. The angiography showing a single coronary emerging anterior and rightward before trifurcating is shown in the video above.

First, a redo midline sternotomy was performed, followed by extensive dissection of the branch PAs and ascending aorta. Waterson's groove was then developed extensively. The site of the planned right atriotomy was then marked. Note that this incision was high toward the atrioventricular (AV) groove, anterior and parallel to the crista terminalis. The patient was cannulated for cardiopulmonary bypass (CPB) using central aortic and bicaval venous cannulation and cooled to 28 degrees. The patent ductus arteriosus (PDA) was then doubly ligated and divided. The PA band was then removed; this site was clearly stenotic. Next, the pulmonary root was dissected. There was a single coronary arising from the right anterior sinus. The right coronary crossed anteriorly and leftward along the aortic annulus and was extensively mobilized. The cross-clamp was applied and antegrade cardioplegia was delivered with good diastolic arrest.

After this, the right atriotomy was performed and the intra-atrial anatomy was inspected. There was noted to be a well-developed Eustachian valve which would be used later for systemic venous baffle construction. The fossa ovalis was incised, and this incision was extended across the interatrial septum, leaving a few millimeters from the mitral valve. The limbus was then incised and excess tissue was aggressively restricted to ensure an unobstructed superior vena cava (SVC) pathway. This incision also created an opening into the pulmonary venous chamber through Waterson's groove, which was then opened and extended inferiorly as possible. Doing this freed up the hinged atrial septal flap. The septal flap was then sutured to the posterior left atrial wall such that all four pulmonary veins were deep in it and the left atrial appendage lay above it. The first layer created the floor of the systemic venous baffle. The coronary sinus was unroofed, thus incorporating into the systemic venous pathway.

Next, the posterior edge of the right atriotomy was rolled forward to create the systemic venous baffle. The first stitch approximated the lateral RA free wall to the septal remnant such that one-third of its length could be used for the inferior vena cava (IVC) and two-thirds for the SVC pathway. This helped ensure maximum volume of the SVC pathway, which is more prone to obstruction. The suture line began inferiorly by suturing the free wall of the RA to the eustachian valve. This was continued superiorly using the septal remnant close to the posterior mitral annulus. The SVC pathway was started at the trabeculated portion of the RA, high above the SVC and continued along the septal remnant to complete the suture line.

Next, the outer baffle was constructed by connecting the free edge of the RA wall to the lateral opening of the pulmonary veins with a patch augmentation. To begin, the ostia of the right superior and inferior pulmonary veins was incised to maximize the opening into the pulmonary venous chamber. An in situ native pericardial patch was used to initially augment the baffle by suturing the pulmonary vein margin to the facing pericardium. Here, care was taken to avoid injury to the phrenic nerve. It was evident that the native pericardial flap was not high enough to reach the RA free edge. Thus, a pulmonary homograft patch was used to complete the outer baffle. The suture line was carried across the cut edge of the RA with the additional patch aiding in construction of an unobstructed pulmonary venous pathway.

Next, the arterial switch was performed and the ascending aorta was transected, revealing a single coronary ostium located in the center of the right anterior sinus. The main pulmonary artery (MPA) was transacted at the prior band site and it was clear that supra-AS would be an issue. The LeCompte maneuver was then performed. A large coronary button was then harvested from the aorta. The anterior sinus of the neo-aorta was incised and the coronary button was implanted. Despite using the large coronary button as an enlargement flap, there was still significant stenosis at the level of the commissures. The neo-aorta was incised in each of the other two sinuses and two small autologous pericardial patches were used to augment the distal aspect of the neo-aortic root. The two-patch sinus enlargement resulted in a dramatic increase in neo-aortic root dimensions. The ascending aorta was then anastomosed to the neo-aortic root in an end-to-end fashion. The site of the coronary button harvest on the neo-MPA was repaired with a patch of autologous pericardium.

Following adequate de-airing, the outer baffle suture line was completed and tied down. The clamp was released with the resumption of its preoperative complete heart block. The neo-MPA was very leftward, thus the left pulmonary artery had to be incised almost to the left lower lobe take-off. The neo-pulmonary artery confluence was then reconstructed with a PhotoFix patch augmentation.

Finally, the patient was weaned off bypass with good hemodynamics and inspection revealed nice geometry of the great vessels and outer baffle. Bypass time was 226 minutes, and clamp time was 137 minutes. Postoperative TEE demonstrated good biventricular function and unobstructed systemic and pulmonary venous baffles. There was trivial AI with no evidence of supra-AS.

Postoperative Course

The patient arrived at the ICU intubated on low dose milrinone. He was extubated on postoperative day one, weaned off milrinone on postoperative day three, and transferred to the floor on postoperative day four. He was discharged home on postoperative day six and continues to do well at the latest follow-up.

References

1. Barron, D. J., Davies, B. (2013). The atrial switch component of the double-switch procedure: Management of venous anomalies and role of the Superior Cavopulmonary Connection. Operative Techniques in Thoracic and Cardiovascular Surgery, 18(3), 190–203. https://doi.org/10.1053/j.optechstcvs.2013.11.001

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