Occlusion of a Sano Shunt Using the Amplatzer Duct Occluder

Many centers are currently adopting the Sano modification of the Norwood operation for infants with hypoplastic left heart syndrome.¹ The insertion of a right ventricle-to-pulmonary artery conduit may increase aortic diastolic pressure and coronary artery perfusion.² In the face of an unexpectedly elevated pulmonary vascular resistance prior to the bidirectional Glenn operation, an additional source of pulmonary blood flow may be required. This situation may arise either intraoperatively, prohibiting shunt takedown, or postoperatively, requiring reoperation and shunt insertion. ^3,4 Once the pulmonary vascular resistance has decreased sufficiently to maintain an acceptable arterial saturation, additional sources of pulmonary blood flow are no longer desirable. Collateral arteries are usually coiled prior to either the bidirectional Glenn or Fontan operation. The occlusion of residual surgical shunts will decrease ventricular volume load and allow the pulmonary vascular resistance to fall.⁵
We report on an infant with a variant of hypoplastic left heart syndrome who underwent a Norwood operation with the Sano modification. The postoperative course was complicated by hypoxic episodes which were thought to be due to a reactive pulmonary vascular bed. A bidirectional Glenn operation was carried out at 4 months, however the Sano shunt was left in situ. This was successfully occluded 1 year post insertion with the Amplatzer Ductal Occluder DeviceTM (AGA medical, Golden Valley, Minnesota).⁶

Case Report. A female infant with a postnatal diagnosis of hypoplastic left heart variant presented to our institution on day 1 of life. There was mitral atresia, severe aortic stenosis, hypoplasia of the ascending aorta (2 mm), aortic coarctation and a restrictive patent foramen ovale. Both of the great arteries were committed to the right ventricle. On day 7 of life, she underwent a stage-1 Norwood operation with coarctation repair, atrial septectomy, left pulmonary arterioplasty, and insertion of a 5 mm Sano shunt. The sternum was closed on postoperative day 4 and successful extubation occurred on postoperative day 10.
Cardiac catheterization prior to the Glenn operation demonstrated mild hypoplasia of the pulmonary arteries, a transpulmonary gradient of 4 mmHg with a normal pulmonary vascular resistance. A bidirectional Glenn operation was carried out at 4 months of age. There were extensive adhesions surrounding the heart and dissection was extremely difficult. There was an inadvertent tear to the confluence of the pulmonary artery which was repaired with a pericardial patch. On weaning from cardiopulmonary bypass there was severe hypoxia, with arterial saturation decreasing to 40%. The Sano shunt was left in situ with a view to providing an additional antegrade source of pulmonary blood flow. Postoperatively, the patient was commenced on Sildenafil and remained intubated for 1 week. She was discharged 3 weeks after surgery with an arterial saturation of 75%.
Procedure Description. The patient underwent cardiac catheterization with a view to occluding the Sano shunt, 8 months later. The arterial saturation pre-catheterization was 85% and blood pressure was 76 x 42 mmHg with a mean of 55 mmHg. Access was obtained form the right femoral vein, right femoral artery and right internal jugular vein. Right atrial pressure was 7 mmHg, right ventricular end-diastolic pressure was 5 mmHg, and the pulmonary arterial pressure was 16 x 5 mmHg with a mean of 11 mmHg. Aortic angiography showed significant systemic-to-pulmonary artery collaterals. A 5 Fr right coronary catheter was passed into the right ventricle and subsequently into the Sano shunt. Angiography showed significant stenosis of the Sano shunt and mild hypoplasia of the left pulmonary artery. The portion of the Sano shunt we elected to place measured 4 mm and 2 mm at two separate points. During manipulation of the catheter, the patient developed 2:1 atrioventricular block, hence manipulations were subsequently performed form the superior vena cava.
A 5 mm Tyshak II balloon was inflated in the Sano shunt and a test occlusion was performed. Arterial saturations dropped from 85% to 77%, and the mean pulmonary artery pressure dropped from 11–8 mmHg. A 0.035 inch guidewire was passed from the superior vena cava through the Sano shunt and into the inferior vena cava. A 6 x 4 mm Amplatzer Ductal Occluder Device was positioned in the Sano shunt using a 5 Fr Amplatzer delivery system (AGA, Golden Valley, Minnesota), with the flat disc facing the right ventricle. An angiogram from the right ventricle showed almost complete occlusion of the Sano shunt. On releasing the device, it expanded to fill the Sano shunt and subsequent angiograms demonstrated complete occlusion. The following day, the patient’s arterial saturation was 80% and an echocardiogram demonstrated complete occlusion.

Discussion. As outlined above, sometimes it is necessary to have an additional source of pulmonary blood flow following a bidirectional Glenn operation.³ Although in the short term this will increase the arterial saturation, over time it will increase volume load on the ventricle. While these residual surgical shunts can be addressed at the time of the Fontan operation, this additional period of volume load may cause unnecessary ventricular dilation.⁷ With a catheter intervention it is possible to test occlude the shunt, assessing arterial saturations and other hemodynamic parameters. A conservative approach would be advised when considering occlusion in view of the relative stability of the pulmonary vasculature under anesthesia. In our case there were many collateral arteries to the upper lobes of both lung fields. In their absence, it may not have been prudent to close the residual shunt in view of the drop in arterial saturation seen during test occlusion.
This case demonstrates how a residual surgical shunt can sometimes be beneficial in negating the effect of high pulmonary vascular resistance in the immediate postoperative period. It may be possible at a later date to perform percutaneous test occlusion and device closure. The flexibility of the Amplatzer Ductal Occluder Device permitted relatively easy deployment through a small sheath. Once released, the device expanded and the larger disc ensured a stable position. The internal polyester strands promote rapid clotting inside the device. An Amplatzer Vascular Plug^™ might have been successful in this situation, however, due to the lack of internal fibers, it may have been less likely to completely occlude the shunt.⁸ An Amplatzer Muscular Ventricular Septal Defect Occluder^™ might also have been used; however, it was our feeling that the shape of the shunt conformed more appropriately to the Amplatzer Ductal Occluder Device.⁹ In conclusion, occlusion of a Sano shunt is feasible with the Amplatzer Ductal Occluder Device. In addition, this is a strategy that can be adopted when it becomes evident during a bidirectional Glenn operation that an additional source of pulmonary blood flow will be required.

References

1. Maher KO, Pizarro C, Gidding SS, et al. Hemodynamic profile after the Norwood procedure with right ventricle to pulmonary artery conduit. Circulation 2003;108:782–784.
2. Sano S, Ishino K, Kado H, et al. Outcome of right ventricle-to-pulmonary artery shunt in first-stage palliation of hypoplastic left heart syndrome: A multi-institutional study. Ann Thorac Surg 2004;78:1951–1957; discussion 1957–1958.
3. Yoshida M, Yamaguchi M, Yoshimura N, et al. Appropriate additional pulmonary blood flow at the bidirectional Glenn procedure is useful for completion of total cavopulmonary connection. Ann Thorac Surg 2005;80:976–981.
4. Lamberti JJ, Spicer RL, Waldman JD, et al. The bidirectional cavopulmonary shunt. J Thorac Cardiovasc Surg 1990;100:22–29; discussion 29–30.
5. Black SM, Bekker JM, McMullan DM, et al. Alterations in nitric oxide production in 8-week-old lambs with increased pulmonary blood flow. Pediatr Res 2002;52:233–244.
6. Faella HJ, Hijazi ZM. Closure of the patent ductus arteriosus with the amplatzer PDA device: Immediate results of the international clinical trial. Catheter Cardiovasc Interv 2000;51:50–54.
7. Gewillig M, Daenen W, Aubert A, Van der Hauwaert L. Abolishment of chronic volume overload. Implications for diastolic function of the systemic ventricle immediately after Fontan repair. Circulation 1992;86(5 Suppl):II93–9.
8. Hill SL, Hijazi ZM, Hellenbrand WE, Cheatham JP. Evaluation of the Amplatzer vascular plug for embolization of peripheral vascular malformations associated with congenital heart disease. Catheter Cardiovasc Interv 2006;67:113–119.
9. Hijazi ZM, Hakim F, Al-Fadley F, et al. Transcatheter closure of single muscular ventricular septal defects using the amplatzer muscular VSD occluder: Initial results and technical considerations. Catheter Cardiovasc Interv 2000;49:167–172.