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Right Ventricle to Pulmonary Artery Shunt

      A shunt from the right ventricle to the pulmonary arteries (RV-PA shunt) is now commonly used in the Norwood procedure.
      • Ohye R.G.
      • Sleeper L.A.
      • Mahony L.
      • et al.
      Comparison of shunt types in the Norwood procedure for single-ventricle lesions.
      • Ballweg J.A.
      • Dominguez T.E.
      • Ravishankar C.
      • et al.
      A contemporary comparison of the effect of shunt type in hypoplastic left heart syndrome on the hemodynamics and outcome at stage 2 reconstruction.
      • Lai L.
      • Laussen P.C.
      • Cua C.L.
      • et al.
      Outcomes after bidirectional Glenn operation: Blalock-Taussig shunt versus right ventricle-to-pulmonary artery conduit.
      The RV-PA shunt is also useful for palliation of selected infants with inadequate pulmonary blood flow prior to a biventricular repair.
      • Bradley S.M.
      • Erdem C.C.
      • Hsia T.Y.
      • et al.
      Right ventricle-to-pulmonary artery shunt: Alternative palliation in infants with inadequate pulmonary blood flow prior to two-ventricle repair.
      The Pediatric Heart Network randomized study of the RV-PA shunt vs the modified Blalock–Taussig shunt in patients undergoing a Norwood procedure found that the RV-PA shunt resulted in better transplantation-free survival 12 months after surgery.
      • Ohye R.G.
      • Sleeper L.A.
      • Mahony L.
      • et al.
      Comparison of shunt types in the Norwood procedure for single-ventricle lesions.
      However, the same study also found that the RV-PA shunt resulted in a higher rate of unintended cardiovascular interventions, primarily balloon dilation or stent placement in the shunt or branch pulmonary arteries.
      • Ohye R.G.
      • Sleeper L.A.
      • Mahony L.
      • et al.
      Comparison of shunt types in the Norwood procedure for single-ventricle lesions.
      Other authors have noted early progression of RV-PA shunt stenosis, particularly at the proximal anastomosis of the shunt to the right ventricle.
      • Ballweg J.A.
      • Dominguez T.E.
      • Ravishankar C.
      • et al.
      A contemporary comparison of the effect of shunt type in hypoplastic left heart syndrome on the hemodynamics and outcome at stage 2 reconstruction.
      • Lai L.
      • Laussen P.C.
      • Cua C.L.
      • et al.
      Outcomes after bidirectional Glenn operation: Blalock-Taussig shunt versus right ventricle-to-pulmonary artery conduit.
      • Simsic J.M.
      • Cuadrado A.
      • Kirshbom P.M.
      • et al.
      Novel management strategy for severe cyanosis after Sano modification of the Norwood procedure.
      This may result in decreasing systemic oxygen saturations and the need for an early stage II procedure. These limitations of the RV-PA shunt may be related to the particular technical details of the shunt placement. This article briefly examines the technique for placement of an RV-PA shunt, focusing on a “side-to-side” technique for the proximal anastomosis. This technique is illustrated for the RV-PA shunt as part of a Norwood procedure. Basically, the same technique may also be used in other situations in which a tube graft is anastomosed to the right ventricle. This would include use of an RV-PA shunt as palliation in infants prior to biventricular repair, and use of an RV-PA conduit such as the bovine jugular vein (Contegra [Medtronic, Minneapolis, MN]) graft during a biventricular repair.

      Operative Technique

      Figure thumbnail gr1
      Figure 1The cardiac anatomy in a patient with hypoplastic left heart syndrome is illustrated. The leaflets of the pulmonary valve are ghosted in; they insert in the right ventricular outflow tract at a lower level than is evident by external examination, an important point to consider in placing the proximal RV-PA shunt anastomosis. External examination ensures that there is no important coronary crossing the outflow tract in the area that will be used for the proximal anastomosis.
      Figure thumbnail gr2
      Figure 2Prior to going on cardiopulmonary bypass, a nonringed, stretch polytetrafluoroethylene (Gore-Tex [W.L. Gore & Associates, Flagstaff, AZ]) tube graft is selected. A graft diameter of 5 mm has been used for patients weighing less than ∼3.2 kg, and a diameter of 6 mm for larger patients. The graft is cut on a bevel (∼45°) and sewn to a disk of pulmonary homograft. The suture line is sewn with 7-0 prolene from the inside and treated externally with fibrin glue (cryoprecipitate + thrombin + calcium), which produces a hemostatic suture line.
      Figure thumbnail gr3
      Figure 3The patient is placed on cardiopulmonary bypass using an arterial cannula placed directly into the innominate artery, and a venous cannula in the right atrial appendage. The arterial cannula is secured with its tip only 1-2 mm inside the innominate artery, so that it provides flow both proximally and distally. Dissection is completed during cooling to 20°C. Pump flow is then isolated to the head and the heart by placing an angled vascular clamp across the proximal arch between the innominate and left carotid arteries, occluding the left carotid and left subclavian arteries with neurovascular clips, and occluding the descending aorta with a small profunda vascular clamp (not shown). The ductal tissue comprising the back wall of the isthmus is excised (coarctectomy), and the back wall of the aorta is reconstructed end to end. All remaining ductal tissue is trimmed anteriorly from the aorta. The main pulmonary artery is transected at the origin of the right pulmonary artery.
      Figure thumbnail gr4
      Figure 4The RV-PA shunt may be placed either to the right or to the left of the reconstructed neoaorta. Placing the shunt to the right facilitates exposure of the distal shunt at the time of the second-stage operation. Placement to the right also generally results in the shunt lying directly behind the sternum. Over time we have evolved to a preference for placement of the shunt to the right.
      If the shunt is to be placed to the left, the disk of homograft with the attached shunt is now sewn to the distal main pulmonary artery (A). Exposure for this to the left is better at this point in the operation than later, once the neoaorta has been reconstructed. The bevel in the disk–shunt junction allows the shunt to pass smoothly from the right ventricle to the posteriorly located pulmonary arteries.
      An alternative for the distal anastomosis is to close the distal pulmonary artery transection site with a homograft patch and place the shunt anastomosis to the anterior central pulmonary artery confluence (B). This option is used if the central pulmonary artery confluence is enlarged and provides a good target for distal anastomosis. Again, if the shunt is to lie to the left of the neoaorta, this step is most easily carried out prior to the construction of the neoaorta.
      Figure thumbnail gr5
      Figure 5The vascular clamp on the proximal arch is then moved to the proximal innominate artery, so that direct pump flow continues only to the head (“regional low-flow perfusion”). The heart is arrested with cardioplegia administered directly down the ascending aorta. The dotted line indicates continuation of the opening in the arch down the ascending aorta. Looking down through the pulmonary valve, a site is selected for the proximal RV-PA shunt anastomosis. The leaflets of the pulmonary valve insert more inferiorly in the outflow tract than can be seen from the outside of the heart. Selecting this site “from the inside” is important for several reasons: the optimal site is well inferior to the pulmonary valve (at least 5 mm) in a thin portion of myocardium, without underlying muscle bundles, and to the right of the interventricular septum. A linear incision is made in the right ventricle with a scalpel over a distance of 6 to 8 mm. Free entry into the right ventricle, inferior to the pulmonary valve, and unimpeded by muscle bundles, is confirmed from both the interior and the exterior of the heart. In general, no muscle is resected from the edges of this incision.
      Figure thumbnail gr6
      Figure 6Construction of the neoaorta is then carried out, including side-to-side anastomosis of the ascending aorta to the main pulmonary artery, and arch reconstruction using pulmonary homograft. If the ascending aorta is <3 mm in diameter, it is sewn side to side to a short incision down the facing aspect of the main pulmonary artery.
      • Tweddell J.S.
      The Norwood procedure with an innominate artery to pulmonary artery shunt.
      A fine stay stitch in the right side of the outflow tract incision provides exposure for the proximal shunt anastomosis. At this point the shunt is trimmed somewhat longer than is needed to reach the proximal site.
      Figure thumbnail gr7
      Figure 7Details of the proximal, “side-to-side,” shunt anastomosis. A straight incision is made up of the back of the shunt to a point exactly approximating the cephalad end of the RV outflow tract incision. The edges of the incision in the shunt are sewn to the right ventriculotomy using running 6-0 Gore-Tex suture on a TTc-9 needle. The bites in the myocardium include both epicardium and endocardium. This technique gives strength to the suture line. It also avoids leaving any muscle underlying the proximal anastomosis, which could potentially cause obstruction over time. Suturing is initially from the inside at the heel and then transitions to the outside. When the 2 suture lines come together at the inferior end of the ventriculotomy, the excess shunt (the anterior corners) is trimmed, and both suture lines are continued to close the remaining opening in the shunt to itself. This “side-to-side” approach results in the proximal shunt lying parallel to the anterior wall of the heart, rather than protruding at an angle. We prefer to do this anastomosis with the heart arrested.
      Figure thumbnail gr8
      Figure 8(A) The completed operation with the shunt lying to the left of the neoaorta. Alternatively, the shunt may be placed to the right side (B). In this case, the proximal shunt anastomosis is carried out first, as in , during myocardial arrest. The distal shunt anastomosis is done subsequently, during rewarming, as exposure of the central pulmonary arteries to the right side of the neoaorta is generally straightforward. Placing the shunt to the right facilitates exposure of the distal shunt at the time of the second-stage operation. It also results in the shunt lying directly behind the sternum, so that placing a piece of Gore-Tex pericardial membrane (Preclude [W.L. Gore & Associates]) between the shunt and the sternum is helpful for the resternotomy.
      This article presents one approach to placement of an RV-PA shunt, focusing on a “side-to-side” technique for the proximal anastomosis. The key points are seen in Figure 5, Figure 7. They include selection of the optimal site for the right ventriculotomy (inferior to the pulmonary valve, clear of muscle bundles, and the interventricular septum), inclusion of both epicardium and endocardium in the proximal suture line (aimed at avoiding subsequent muscular obstruction of the proximal shunt), and positioning of the proximal shunt parallel to the RV free wall. The side-to-side approach contrasts with alternative techniques. These techniques are illustrated for the RV-PA shunt as part of a Norwood procedure. We have found the side-to-side approach to the proximal RV-PA anastomosis to be useful in other situations in which a tube graft is anastomosed to the right ventricle. These have included the use of an RV-PA shunt as palliation infants prior to biventricular repair,
      • Bradley S.M.
      • Erdem C.C.
      • Hsia T.Y.
      • et al.
      Right ventricle-to-pulmonary artery shunt: Alternative palliation in infants with inadequate pulmonary blood flow prior to two-ventricle repair.
      and the use of the bovine jugular vein (Contegra) graft as an RV-PA conduit during a biventricular repair.
      • Dave H.
      • Dodge-Khatami A.
      • Kadner A.
      • et al.
      Modified technique for heterotopic implantation of a right ventricular outflow tract conduit.

      References

        • Ohye R.G.
        • Sleeper L.A.
        • Mahony L.
        • et al.
        Comparison of shunt types in the Norwood procedure for single-ventricle lesions.
        N Engl J Med. 2010; 362: 1980-1992
        • Ballweg J.A.
        • Dominguez T.E.
        • Ravishankar C.
        • et al.
        A contemporary comparison of the effect of shunt type in hypoplastic left heart syndrome on the hemodynamics and outcome at stage 2 reconstruction.
        J Thorac Cardiovasc Surg. 2007; 134: 297-303
        • Lai L.
        • Laussen P.C.
        • Cua C.L.
        • et al.
        Outcomes after bidirectional Glenn operation: Blalock-Taussig shunt versus right ventricle-to-pulmonary artery conduit.
        Ann Thorac Surg. 2007; 83: 1768-1773
        • Bradley S.M.
        • Erdem C.C.
        • Hsia T.Y.
        • et al.
        Right ventricle-to-pulmonary artery shunt: Alternative palliation in infants with inadequate pulmonary blood flow prior to two-ventricle repair.
        Ann Thorac Surg. 2008; 86: 183-188
        • Simsic J.M.
        • Cuadrado A.
        • Kirshbom P.M.
        • et al.
        Novel management strategy for severe cyanosis after Sano modification of the Norwood procedure.
        J Thorac Cardiovasc Surg. 2005; 129: 1450-1451
        • Tweddell J.S.
        The Norwood procedure with an innominate artery to pulmonary artery shunt.
        Op Tech Thor Cardiovasc Surg. 2005; 10: 123-140
        • Dave H.
        • Dodge-Khatami A.
        • Kadner A.
        • et al.
        Modified technique for heterotopic implantation of a right ventricular outflow tract conduit.
        Ann Thorac Surg. 2006; 81: 2321-2323