Double-root transfer and the half-turned truncal switch

Abstract

Transposition of great arteries (TGA) or double-outlet right ventricle (DORV) with ventricular septal defect (VSD) and pulmonary stenosis (PS) is a complex congenital cardiac malformation, which can be treated by both univentricular and biventricular pathways. Biventricular repair includes Rastelli operation, reparation a l’etage ventriculaire (REV), pulmonary root translocation, and Nikaidoh procedures. Double-root translocation (DRT) technique and half-turned truncal switch technique (HTTS) are being considered as useful alternatives. In this review, we will see in detail about DRT and HTTS.

Introduction

Transposition of the great arteries (TGA) or double-outlet right ventricle (DORV) with ventricular septal defect (VSD) and pulmonary stenosis (PS) is a complex congenital cardiac malformation, with varied treatment options [1]. Biventricular repairs of this complex heart defect include Rastelli operation, reparation a l’etage ventriculaire (REV), pulmonary root translocation, and Nikaidoh procedures. Of late, the double-root translocation (DRT) technique and half-turned truncal switch (HTTS) technique are being considered as useful alternatives. These techniques are developed to overcome suboptimal long-term outcomes of the conventional procedures such as Rastelli and REV. Double-root translocation comprises aortic root translocation and pulmonary root translocation, with the use of the pulmonary root thereby avoiding the problems of growth and degeneration of the right ventricular outflow tract (RVOT) conduits used normally [2]. In HTTS, the aorta and the pulmonary root are removed en bloc and rotated 180° so that the aorta and pulmonary artery (PA) arise from their respective normal ventricles [3]. In this review, we will go through the history, indications, techniques, timing, complications, advantages, and disadvantages of DRT and HTTS procedures.

History

In 1969, the Rastelli procedure [1] became the first successful operation for TGA with VSD and PS that incorporated the left ventricle as the systemic ventricle for correction of TGA and therefore was called anatomic correction.

In the original description, the procedure involved baffling of the VSD to the aorta and connection of the right ventricle to the pulmonary artery with a homograft conduit.

However, the Rastelli procedure, an epic landmark of pioneer in cardiac surgery, is far from being an anatomic correction since the right ventricle is connected to the pulmonary artery with a prosthetic conduit that in most cases will become obstructed.

In 1984, Nikaidoh [4] proposed the idea of aortic translocation and biventricular outflow tract reconstruction for the management of transposition of the great arteries with VSD and PS. This repair consists of harvesting the aortic root from the right ventricle (with attached coronary arteries), relieving the left ventricular outflow tract obstruction (LVOTO) (dividing the outlet septum and excising the pulmonary valve), reconstructing the left ventricular outflow tract (with the posteriorly translocated aortic root and the VSD patch), and reconstructing the right ventricular outflow tract (with a pericardial patch). Although technically challenging, this approach results in a more normal anatomic repair. With the evolution of aortic translocation techniques, it has exceptionally been performed in cases of DORV with sub pulmonary VSD and PS.

In 2003, Yamagishi et al. [5] came up with an innovative technique, HTTS as an alternative to conventional procedures such as Rastelli and REV procedures. Late left ventricular outflow tract obstruction following Rastelli is entirely avoided with this technique because a wide and straight left ventricular outflow tract is provided by means of posterior translocation of the ascending aorta and because the systemic bloodstream is not passed through either the VSD or the intraventricular tunnel.

Da Silva [6, 7] and coworkers proposed pulmonary root translocation in a modified Rastelli-type repair. They removed the pulmonary root with the valve and translocated it with or without a transannular patch enlargement, depending on the “Z” score.

Hu et al. [2] from Fuwai hospital, Beijing, came up with a new operation, double-root translocation, which comprises aortic and pulmonary root translocation. It aims at retrieving the normal geometry of the left and right ventricle outflow tract, while at the same time maximally preserving the function and growth potential of the aortic and pulmonary valves [2]

Indications and extended indications of DRT and HTTS [8]

• TGA VSD PS

• DORV/double-outlet left ventricle (DOLV)/VSD PS

• Congenitally corrected transposition of great arteries (CCTGA) VSD PS.

Other indications

• Where Rastelli (the gold standard option)/REV/arterial switch operation (ASO) and left ventricular outflow tract (LVOT) resection, either not possible or not preferred by the surgeon, e.g., remote VSD (non-committed VSD)/straddled atrio-ventricular (AV) valves/smallish RV.

• DRT and HTTS are very much useful in situations wherein the VSD is remote precluding any other options of two ventricle repairs like REV or Rastelli.

• However, the indications have expanded to CCTGA PS; herein, the PA is not suitable for a switch-Senning option.

Pre-requisite for surgery (DRT and HTTS) [2, 3, 8]

• The best time for these operations is usually 6 months and above and should take into account various factors such as the degree of cyanosis, experience of the unit, and the individual anatomy.

• Though no ideal weight has been defined, authors prefer more than 6 kg since the cardiopulmonary bypass is better tolerated in higher weight.

• Considering that the bypass run, and cross clamp run are likely to be high with manipulation of coronaries, extreme care and attention to myocardial protection is essential. Also, despite everything, backup of mechanical heart assist may be required.

• Two good-sized ventricles must be present.

• Coronary anatomy pattern should be known in detail preoperatively, one should be cautious in case of a major coronary, such as left anterior descending (LAD), crossing the RVOT (which is a relative contraindication).

Operative technique

Double-root translocation technique [9] (Fig. 1)

Fig. 1.

Operative steps in DRT. a Anatomy assessed: anteroposterior relationship of the great arteries with the aorta in front. b The aorta transected with explantation of single or both coronary button. c Dissection of pulmonary root and performance of Lecompte maneuver. d VSD closure through RVOT. e The aorta, anastomosed posterior into the LVOT with reimplantation of coronary button/s (one/both). f The pulmonary artery is then anastomosed onto the RVOT and anteriorly augmented with pericardium

The operation described below is our preferred technique currently, wherein the left coronary artery (LCA) myovascular pedicle is not harvested. The right coronary artery (RCA) button is explanted in an owl eye fashion, and not as a flap or U button as in arterial switch operation.

The heart is approached via a median sternotomy and pericardiotomy. At this stage, any shunt is dissected and the relationship of the aorta and pulmonary artery and the coronary anatomy is inspected to ensure that the case is suited for a double-root translocation. Any systemic–pulmonary shunt is dissected at this stage along with the mobilization of the pulmonary arteries.

Cardiopulmonary bypass (CPB) is established using high aortic and bicaval cannulation. On CPB, the pulmonary artery mobilization and dissection of the aorta from the main pulmonary artery can be completed. patent ductus arteriosus (PDA) is ligated and transected. The aorta and proximal arch are mobilized to ensure a tension-free anastomosis during the reconstruction of the transected aorta. The patient is cooled to 28 °C, and the heart arrested using cold blood cardioplegia (custodial or del Nido is our preference).

The right atrium (RA) is opened, and the interatrial septum (IAS) is stabbed, and a vent introduced into the left atrium (LA). The VSD is inspected from the RA through the tricuspid valve (TV) mainly to assess the size, location, and straddling. The aorta is transected above the ST junction, and a ring of aortic tissue is taken, if the aorta is dilated or looks redundant. The RCA button is harvested and RCA mobilized. The VSD is again inspected through the aorta, and a right angle is introduced through the aortic valve, and the right ventricle (RV) muscle tented 5–8 mm beyond the annulus of aortic valve. The right ventriculotomy is then extended on both the sides taking care not to extend too close to the LAD on the left side and also making sure that the cuff of the muscle is not too close to aortic annulus.

We then extend the dissection below the RCA, which becomes easy, and this incision is extended between the muscle conus between the aortic and the pulmonary annulus.

In TGA situations, where there is no conus tissue between the pulmonary valve (PV) and mitral valve (MV), we stay close to the pulmonary valve and if necessary sacrifice the posterior cusp of the PV in order to stay clear of the circumflex artery and the mitral valve in particular.

The Lecompte is then performed.

VSD is closed using synthetic or bovine patch through the right ventriculotomy.

The left coronary myovascular pedicle is left intact, and the root, which is almost two thirds harvested, is rotated and translocated posteriorly and sutured to the pulmonary mitral junction onto the fibrous tissue. The anterior cuff is sutured to the VSD patch. The aortic root, after reconstruction, should be at the same plane as the right ventriculotomy. The right coronary button is then reimplanted onto the aortic defect or on to a new location, without any tension from stretching or kinking.

Cross clamp is then removed after closure of RA, and the pulmonary root is implanted onto the right venticulotomy after addressing the valve cusps and annulus size issues by appropriate technique to ensure low gradients and low regurgitation of the pulmonary valve. The patient is slowly weaned off with ionotropic supports after inserting two atrial and two ventricular wires.

We do not put LA lines and leave the chest open in selected cases as per the duration of bypass, bleeding status, and myocardial edema; however, in most cases, chest closure is possible. Majority of patients can be weaned off the ventilator within 24 h.

Technical details and precautions to be taken

Coronary mobilization vs coronary transfer

It depends upon the degree of posterior translocation which in turn depends on pulmonary annulus and conal septum thickness. In general, coronary transfer is considered more safe since there is significant risk of coronary stretching and ischemia in mobilization alone, especially if there is significant translocation. Relationship of the aortic and pulmonary annulus to each other also plays significant role in coronary anatomy. If the aortic and pulmonary annuli are not anteroposterior, then aortic annulus does not shift directly posteriorly in a straight line, but to the right or left depending on the location of pulmonary annulus. This could induce a twist in the aortic root, if geometry is not maintained, and can also lead to twist in coronary, apart from stretching.

Below is the conventional operation described in diagrams.

Half-turned truncal switch [5, 10] (Fig. 2)

Fig. 2.

Operative steps in half-turned truncal switch. a The aorta and pulmonary trunk resected. b Coronory orifice harvested. c, d Harvestation of truncal block. e Closure of the VSD. f The truncal block is half-turned (arrows showing it). g The aorta anastomosed to LVOT. h Reconstruction of RVOT

Initial steps and principle of the surgery were described in detail above. Important steps relevant to HTTS procedure alone are listed below.

Stay sutures are placed at the aortic root anteriorly and pulmonary root posteriorly. Coronary buttons are harvested. The runcal block including both semilunar valves is resected. The conus septum is either totally resected together with the aortic and pulmonary root or partially resected and divided. The truncus block is rotated by 180° and reimplanted, so that aortic valve is located on the left ventricular opening, and the pulmonary root comes over the RVOT. After implanting the posterior part of the aortic root, the LVOT is completed by closing the VSD with a patch. The LVOT is thereby enlarged to its appropriate size. It is important to carry out the suture line to both ends of the divided or resected conus septum at this level. By doing so, the residual circumference of the aortic root can determine the exact width of the VSD patch. Both the coronary buttons are anastomosed to their contralateral orifices at this stage of operation. A Lecompte maneuver is performed, and the anastomosis between the aortic root and ascending aorta is made. Pulmonary root and RV are then anastomosed. Finally, the pulmonary root and PA are reconnected.

Complications of DRT and HTTS [2, 3, 8].

Bleeding

Mitral regurgitation

Coronary ischemia

Neoaortic regurgitation

Heart block

Mechanical circulatory support from low cardiac output

Discussion and review of literature

Rastelli and REV procedures are the most common surgical procedures to correct DORV/TGA VSD and PS but showed disappointing late outcomes for LVOT and RVOT. Kreutzer et al. [11] published a series of 101 Rastelli procedures over a period of 25 years. They reported 17 late deaths, 11 reoperations for LVOT obstruction, 44 conduit reoperations, and 28 conduit reinterventions. They concluded that the presence of straddling tricuspid valve appears to be a risk factor for early and late mortality, and the prevalence of early and late arrhythmia is high after Rastelli repair.

A remote VSD is essentially a contraindication for both the procedures. In brief, neither Rastelli nor REV procedure can meet the expectation of a perfect biventricular outflow tract reconstruction [11, 12]. To overcome the limitations of these procedures and to improve the results, DRT and HTTS techniques were introduced. Both are evolutionary techniques to address DORV/TGA PS with even remote VSD. The advantages of these technique are distinct and several. The LVOT is constructed with a simple VSD patch repair, not as a long intracardiac tunnel resulting in significant reduction in the risk of subaortic obstruction and impairment of left ventricular function. The flow pattern in LVOT is more streamlined compared to the classical procedures. Subsequent need for reoperation is reduced, and survival benefits are anticipated. A double-root translocation is like the Nikaidoh but preserves the integrity of the pulmonary root in addition to the aortic root, shifting it toward the RV and obviating the need for a conduit to reconstruct the RV outflow tract. The overall experience with DRT and HTTS is somewhat limited, and there are just a few reports in the medical literature.

In 2007, Hu and colleagues [13] reported the DRT technique in 40 consecutive cases which comprised aortic root translocation and pulmonary root translocation with use of the pulmonary root, enlarged by a transannular patch of the bovine jugular vein. TGA with VSD and PS were diagnosed in 30 patients (4 with atrioventricular discordance) and double-outlet right ventricle (Taussig-Bing anomalies) with PS in 10 cases (1 with atrioventricular discordance). Four patients required extra corporeal membrane oxygenation (ECMO) support in their series, two of which recovered and two patients died. The causes of death were left ventricular dysfunction caused by left coronary artery insufficiency and renal failure and sepsis caused by severe hemolysis a complication of ECMO.

They concluded that the DRT technique was feasible and effective in treating DORV/TGA, VSD, and pulmonary stenosis. They subsequently reported good early results and normal heart function with physiologic LVOT flow; 13 patients (30%) had moderate pulmonary valve regurgitation, and one patient had mitral and aortic valve regurgitation.

From our own experience of 12 patients with a mean 2 years (1 year to 3 years) of follow-up, we had no early mortality and one late mortality at 6 months after surgery due to severe mitral regurgitation.

Trivial MR was observed in 2 patients in the follow-up period. One patient developed severe TR and was taken back later for surgery. (The straddled chordae of tricuspid valve, which was detached and reimplanted, had a dehiscence resulting in severe TR.)

Mean ejection fraction was 55.87 ± 7.29%. All patients were in sinus rhythm and in NYHA class 1 at follow-up.

Meng et al. [14] reported a case of a 2-year-old girl who underwent successful biventricular repair for transposition of the great arteries, ventricular septal defect, and LVOT obstruction with moderate pulmonary stenosis of the bicuspid pulmonary valve (Z score of − 4.9 for the pulmonary valve) by means of a modified Nikaidoh procedure with double-root translocation using a valve-spared pulmonary root. The results showed no LVOT obstruction, no aortic valve regurgitation, mild pulmonary stenosis, and pulmonary valve regurgitation. No reintervention has been required during the 5-year follow-up, with annular growth of the pulmonary valve.

Similarly, Sakamoto et al. [15] published their experience in one case with modified Nikaidoh procedure and DRT using a valve-sparing pulmonary root technique. Cardiac catheterization 1 year later confirmed a good LVOT, without aortic insufficiency and an acceptable right ventricular outflow tract. They reported that the valve-sparing pulmonary root translocation may be feasible and effective for patients with a pulmonary annulus having a Z score of approximately − 4, even when DRT is performed.

DRT (Table 1) technique has its potential advantages like pulmonary valve growth, thus avoiding the need of other conduits and its problems. Reoperations can be avoided, and it has the advantages of Nikaidoh Bex (aortic root translocation) on LVOT geometry [16]. On the other hand, DRT operation itself involves several intracardiac key structures and thus requires a thorough understanding of the anatomy of complicated congenital heart disease as well as is technically demanding. A long learning curve is anticipated.

Table 1.

Salient features of DRT VS HTTS

DRT	HTTS
S.HU	Yamagishi and Mair
Aortic root and pulmonary root are harvested separately	Both are harvested en bloc with 180° rotation
Coronary button does not always need transfer	It always needs transfer
Aorto-pulmonary continuity disrupted	It is preserved
Growth Potential preserved	Growth potential preserved
Can be performed even if anteroposterior relationship not present	May be done, but with difficulty

The half-turned truncal switch operation can be done in patients with TGA/VSD and TGA-type DORV with mild to moderate LVOT obstruction. Patients with bicuspid pulmonary valve and degenerated pulmonary valve due to previous PA banding can also undergo HTTS. It can be done even in patients with remote VSD. However, it is contraindicated in patients with pulmonary atresia and severe PS. HTTS can be done in most coronary patterns, except when it runs in front of the RVOT (Yacoub types E and F).

Half-turned truncal switch procedure overcomes various drawbacks of the conventional procedure and takes on the advantages of aortic root translocation procedure. After HTTS, both RVOT and LVOT would be straight with non-turbulent flow across them.

Hongu et al. [17] (Table 2) reported 14 patients who underwent HTTS operation. Only one patient had mortality due to arrhythmia, with 13 patients surviving with no coronary insufficiency and no outflow tract obstruction. Their median follow-up was 5.2 years.

Table 2.

: Recent series describing outcomes following DRT and HTTS

Author	Year	Number of patients	Median/mean follow-up (months)	Median/mean age (years)	Mean weight (Kg)	Early mortality	Late mortality	Reintervention
Hu et al. (DRT) [2]	2010	10	20	4.8 ± 5.5	16.3 ± 12.7	Nil	Nil	Nil
Mair et al. (HTTS) [18]	2015	19	153 days to 9.96 years	0.39	5.6	1	1	3
Fang et al. (HTTS) [10]	2010	11	15	10 months to 22 years	15.9	Nil	Nil	Nil
Hongu et al. (HTTS) [17]	2018	14	5.2 years	1.2	8.3	Nil	1	3

Mair et al. [18] (Table 2) reported 19 cases with TGA/DORV VSD PS who underwent HTTS operation. In their series, the pulmonary valve could be preserved in 15 cases, whereas a transannular patch was necessary in 4 cases. They had one early and one late death. Three patients required reoperation, one each for aortic valve repair, VSD closure, and permanent pacemaker implantation.

Conclusion and summary

Root translocation is technically demanding operation and is the best suited biventricular repair in patients with remote ventricular septal defect and TGA/DORV subset. Intermediate-term results of DRT and HTTS look promising and indications are expanding.

With this type of surgical repair (root translocations/HTTS), patients with complex congenital heart diseases can have better outcomes when compared to those with earlier surgical techniques.

Even though there is high morbidity involved in these types of surgical repairs, patients have a better long-time survival and benefits with less chances of reoperations.

Funding

Nil

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics approval and consent to participate

Not applicable being a review article.

Statement of Human and animal rights

Not applicable being a review article.