Influence of Shunt Type on Pulmonary Artery Growth after Norwood Procedure

Objectives: The Norwood (NW) procedure with right ventricle-to-pulmonary artery (RV-PA) shunt is thought to improve the postoperative outcome for patients with hypoplastic left heart syndrome (HLHS), having a favorable effect on the development of the pulmonary arteries (PAs). This study aimed to compare the PA growth between patients who received RV-PA shunt and those with modified Blalock–Taussig shunt (mBTS).

Methods: All consecutive patients with HLHS who underwent the NW procedure between 2001 and 2017 were included in the study. The patients were divided into group A (RV-PA) and group B (mBTS). Prestage 2 angiograms were used to measure the size of the PA. The Nakata index was calculated to estimate PA growth. A ratio of right PA to left PA cross-sectional area (RPA/LPA) was used to calculate the difference between the extents of growth of both branches. Shunt failure was defined as shunt dysfunction due to thrombosis or stenosis requiring intervention or reoperation; shunt mortality was defined as death due to shunt dysfunction.

Results: A total of 223 HLHS patients (group A = 137 and group B = 86) underwent the NW procedure and 190 (group A = 120 and group B = 70) achieved the stage 2 procedure. Freedom from shunt-related mortality after NW was 99.2 ± 1 and 97.6 ± 1.7% at 6 months in groups A and B, respectively (p = 0.09). PA growth was better in group B (Nakata index: group A = 282, group B = 315 mm²/m², p = 0.02). LPA growth was worse compared with the RPA growth in both groups (RPA/LPA: group A = 1.21 and group B = 1.29, p = 1.0). Group A experienced more frequently shunt stenosis (group A = 26 and group B = 2, p < 0.01). The freedom from shunt failure was 83.3 ± 3.2 and 94 ± 2% at 6 months in groups A and B, respectively (p = 0.003).

Conclusion: PA growth was significantly better in patients who received mBTS. Moreover, patients with RV-PA shunt had more frequently shunt failure because of shunt stenosis. However, survival after NW procedure was not shunt dependent and growth of the LPA was less pronounced than of the RPA, regardless of the shunt type.