Technical and anatomical factors affecting the size of the branch pulmonary arteries following first-stage Norwood palliation for hypoplastic left heart syndrome

Abstract

Branch pulmonary artery (BPA) size is one of the factors that influence the efficacy of the Fontan circulation. Central pulmonary artery stenosis and small left pulmonary artery (LPA) are well-known problems following Norwood palliation for hypoplastic left heart syndrome (HLHS). We investigated anatomical and technical factors that may stand behind these problems. A total of 47 consecutive patients were included in the study. All had complete magnetic resonance imaging (MRI) study pre-second-stage palliation. Measurements were taken using a first-pass 3D angiography technique after intravenous injection of an extravascular contrast agent. Factors investigated included the following: size and site of the pulmonary artery bifurcation stump in relation to the Damus-Kaye-Stansel (DKS) anastomosis, interaortic distance/ratio (neoaorta to descending aorta distance/antero-posterior dimension of the chest) (IAD/IAR), distance from the under surface of the arch and the size of native aorta and pulmonary artery. IAD/IAR were compared between two different arch reconstruction techniques. Stenosis occurred either centrally, at the origin of the BPA, or more distally, in the mid-LPA (posterior to DKS). There was a significant lower incidence of central BPA stenosis when the pulmonary artery stump was placed in the mid-position compared with right/left position (26 vs 67%; P = 0.011). A more bulky pulmonary artery stump was also found in those patients with central BPA stenosis (186 vs 137 mm(2)/m(2); P = 0.047). The mid-LPA consistently showed antero-posterior compression (mean cranio-caudal diameter 3.82 mm vs mean antero-posterior diameter 3.07 mm, P < 0.001). Indexed mid-LPA area was only correlated with IAD/IAR (r = 0.49 and 0.51, P < 0.001). No correlation was shown with the distance to the under surface of the arch (r = 0.14, P = 0.37), again confirming antero-posterior compression of the LPA rather than cranio-caudal. In multivariable analysis, the only predictor of indexed mid-LPA area was the IAR (P < 0.001). There was no significant difference in the IAD or IAR between the two arch reconstruction techniques [mean IAD 15.5 vs 13.5 mm (P = 0.14)]; [mean IAR 0.17 vs 0.19 (P = 0.21)]. Of all studied factors, IAR and the size and position of the pulmonary artery bifurcation plays the main role in LPA growth and central BPA stenosis.