Half-Turned Truncal Switch Operation for Transposition of the Great Arteries With Left Ventricular Outflow Obstruction

The half-turned truncal switch operation is suitable for transposition of the great arteries (TGA) or TGA-type double outlet right ventricle (DORV) with left ventricular outflow obstruction, anteroposterior relationship of the great arteries, and mild-to-moderate pulmonary stenosis. A pulmonary-aortic annular diameter ratio of 0.3 to 0.8 is most preferable. This operation, which is not affected by the size or location of the ventricular septal defect (VSD), may also be indicated for patients with a remote or small VSD. Both wide and straight ventricular outflow tracts can be reconstructed by the half-turned truncal switch operation. First, both great arteries are divided and both coronary arterial buttons are resected. The truncal block, including both semilunar valves, is resected. The truncal block is half-turned horizontally, so that the aortic valve is located on the left ventricular opening. Both coronary cuffs face the opposite aortic wall defects after half-turning. After the pulmonary bifurcation is translocated anteriorly, the aortic valve is anastomosed to the left ventricular opening and both coronary cuffs are anastomosed. The right ventricular outflow tract is augmented by commissurotomy or an expanded polytetrafluoroethylene monocuspid patch.

This video demonstrates the author’s approach for this procedure. The patient’s pulmonary leaflets were thick and the pulmonary annular diameter was only 60% of the normal aortic annular diameter (under -2.0 SD). Moreover, subvalvular muscular stenosis was also present. The pressure gradient between the left ventricle and pulmonary artery was 64 mm Hg. Therefore, the surgical team chose the half-turned truncal switch operation instead of an arterial switch operation with VSD closure. The half-turned truncal switch operation can be indicated for patients with mild to moderate pulmonary stenosis, in which the pulmonary-aortic annular diameter ratio ranges from 0.3 to 0.8; this patient’s ratio was 0.49.

The aorta was transected about 5 mm above the coronary orifices. The pulmonary artery was also divided horizontally just before the bifurcation. The anterior wall of the right ventricular outflow tract beneath the aortic annulus was incised horizontally. The incision line was placed a few mm away from the aortic annulus. The infundibular septum was incised transversely. In cases where the VSD is located at a subarterial position, the incision line may extend to the VSD edge. The midline of the mitral-pulmonary fibrous continuity was incised. The truncal block, including both semilunar valves, was resected. The truncal block was half-turned horizontally, so that the aortic valve was located on the left ventricular opening. The width of the superior margin of the Gore-Tex® patch was adjusted to the required length for aortic annular augmentation.

The position of the truncal block should be carefully adjusted so that the coronary cuff faces the opposite aortic wall defect. In order to prevent coronary distortion, the aortic valve should be anastomosed at a slightly higher position around the left coronary artery. On the posterior aspect, the aortic valve was anastomosed to the mitral annulus. The superior margin of the Gore-Tex® patch was trimmed, and the stump of the infundibular septum was anastomosed to the superior margin of the Gore-Tex® patch. The crescent-shaped aortic wall patch was anastomosed to the inferoanterior aspect of the left-sided aortic wall defect. A supplement to the right-sided aortic wall defect was unnecessary. Neither coronary artery was bent or stretched. After anterior translocation of the pulmonary bifurcation, the posteriorly translocated ascending aorta was reconstructed. The pulmonary valve was anastomosed to the right ventricular outflow tract. The anteriorly translocated pulmonary bifurcation was anastomosed to the distal stump of the pulmonary trunk without any supplementary material.

Nonturbulent blood flow and very low energy loss were verified by fluid dynamic analysis after the half-turned truncal switch operation and are compared to fluid dynamics after a Rastelli operation. High wall shear stress by turbulent blood flow may cause intimal damage and subsequent stenotic lesion. Nonturbulent blood flow and low energy loss were also verified at the right ventricular outflow tract. Although the half-turned truncal switch operation is a more invasive surgical procedure, ideal configuration and hemodynamics can be established by maximal use of autologous tissue.

Suggested Reading

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5. Mair R, Sames-Dolzer E, Innerhuber M, Tulzer A, Grohmann E, Tulzer G. Anatomic repair of complex transposition with en bloc rotation of the truncus arteriosus: 10-year experience. Eur J Cardiothorac Surg. 2016;49(1):176-182.
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