Technical Details of a Novel Surgical Procedure for Construction of the Modified Blalock–Taussig Shunt (UKC’s Modification): A Video Presentation

INTRODUCTION

Despite advances in the surgical correction of complex cyanotic congenital heart disease, the construction of systemic-to-pulmonary artery shunt remains necessary, mostly as the first stage of palliation.^[1-6] Although the traditional modification of the classical Blalock–Taussig (BT) shunt using a polytetrafluoroethylene conduit (W.L. Gore Inc., Elkton, MD, USA) remains the systemic-to-pulmonary artery shunt of choice in our institution, we encountered a subset of patients whom we considered unsuitable for this traditional approach. Patients with a right or left-sided aortic arch and right-sided descending thoracic aorta, those with disproportionately small right and left subclavian arteries, smaller than the proposed size of the synthetic graft, and those with anomalies of systemic venous drainage masking the origin of the great arterial branches constitute the ideal candidates for our suggested modification of the construction of a modified BT shunt.^[7]

We did not perform central aortopulmonary shunt in this subset of patients due to the unacceptably high incidence of post-central shunt complications documented in the published literature, namely, congestive cardiac failure, thrombosis, and pulmonary arterial distortion.^[3,8,9]

As yet, there is no full proof formula for choosing an optimal surgical approach, nor is there a given diameter for the shunt in any individual patient. Although an approach through a median sternotomy has been popularized for the construction of central shunts by some investigators, we achieved the same objectives by approaching them through thoracotomy.^[3,9-11] In patients with double aortic arch, the minor aortic arch was transected and anastomosed to the intrapericardial pulmonary artery.^[7]

We approached through a left thoracotomy in all our patients with double aortic arches, in those with the right aortic arch and the right-sided heart, in those with the left aortic arches but right-sided descending thoracic aorta, and in a patient with hemiazygos continuation of an interrupted inferior caval vein, a left superior caval vein, and a right-sided heart.^[7]

In addition, in all patients, the shunt was anastomosed to the intrapericardial pulmonary artery due to its wider caliber and the capacity to provide near-uniform flow to both pulmonary arteries, facilitating symmetrical pulmonary artery growth on both sides.

Thus, there were six forces driving our criteria for the selection of the patients, who subsequently entered our group for further study.

Those with anomalies of the aortic arch and its branches.

• The finding of disproportionately small subclavian arteries

• Variations in the morphology of the aortic arch and its branches, and the systemic veins, which in our judgment precluded construction of the modified BT shunt in conventional fashion

• The desire to use a short segment of polytetrafluoroethylene graft

• The desire to place the pulmonary end of the anastomosis onto the pulmonary trunk or its bifurcation to facilitate symmetrical pulmonary artery growth on both sides, and,

• To avoid the use of cardiopulmonary bypass.

In our study group, the pulmonary arterial diameters were following:

• The ratio of diameter of the pulmonary artery to aorta of <0.75

• McGoon’s ratio of <1.0

• Nakata’s pulmonary artery index of <100 mm², <200 mm², or <250 mm² in patients with tetralogy of Fallot, those future candidates for a Rastelli procedure, or those with a functionally univentricular heart, respectively

• Very small confluent pulmonary arteries in patients below one year of age, the right and left pulmonary arteries ranging from 1 mm to 3 mm in diameter.

Patients with previously placed shunts, pulmonary arterial stenosis at their origin, non-confluent pulmonary arteries, and those undergoing rapid two-stage arterial switch operation were considered unsuitable candidates for our modification of the modified BT shunt.

In the year 2006, we published the technical details and results of further modification of the modified BT shunt on 92 selected patients aged from 7 days to 3.6 years (mean 7.08 ± 6.16 months).^[7]

In 2009, we published our results in ATS of the second stage procedures on these patients, demonstrating, in particular, the symmetrical pulmonary artery growth pattern and ease of takedown.^[12]

In 2006, we published the technical details and results of further modification of the modified BT shunt on 92 selected, heterogenous cohort of symptomatic cyanotic neonates, infants, and preschool children with cyanotic congenital heart disease. These patients were aged from 7 days to 3.6 years (mean 7.08 ± 6.16 months) not amenable either to primary intracardiac repair or to the construction of bidirectional cavopulmonary connection.^[7] These patients had specific anatomic situations contraindicating the usual technique for the construction of the modified BT shunt.^[7]

Subsequently, between 2006 and 2022, we performed an additional 82 UKC’s shunting procedures in various symptomatic cyanotic patients of the entire cohort. One hundred and ten patients underwent a second-stage operation, with 27 receiving a superior cavopulmonary connection, 29 a total cavopulmonary connection, and 54 proceeding to biventricular repair after a mean interval of 25.8 months. We have 21 patients awaiting their second or final stage palliation.

The pulmonary arteries grow as a result of the complex interaction of several factors, such as their initial size, the size of the shunt, and the direction of flow of blood proximal and distal to the site of anastomosis of the shunt.^[13-18] We observed adequate growth of the pulmonary arteries, which were symmetrical and compared favorably with other reported series on the central aortopulmonary shunt.^[3,8-11] Published literature documents an occurrence of pulmonary artery distortion ranging from zero to one-third in patients with a traditionally modified shunt^[2,8,13,14] and from zero to three-fourths of those receiving a classic shunt.^[1,6] Should they occur due to their distal location, the distorted arteries are difficult to repair. When observed in our patients, the distortion was easily repaired due to their central location.

We describe here-in the surgical technique on a 2.5-year-old male child weighing 10 kg diagnosed with a functionally univentricular heart, disproportionately small right subclavian artery, and hypoplastic pulmonary arteries (Mc Goon’s ratio of <1.0).^[5] We interposed a short segment of polytetrafluroethylene graft between the right brachiocephalic artery and the intrapericardial portion of the right pulmonary artery closest to the bifurcation of the pulmonary trunk on the right side. The postoperative recovery was uneventful.

SURGICAL TECHNIQUES

CONCLUSION

Patients deemed unsuitable for the construction of the shunt in traditional fashion are considered for our modification.^[1]

The palliation provided by these shunts is satisfactory, with predictable growth of the pulmonary arteries without significant distortion and easy take-down.^[1] Our modification may be considered from the perspective of a complementary technique for central shunting and not a competitive one.