Objective: The purpose of this study was to determine the relationship between central (proximal branch) pulmonary arteries sizes and differential perfusion of the lungs in conotruncal heart defects using magnetic resonance imaging (MRI).
Methods: In total, 26 patients with conotruncal heart defects underwent cardiovascular MRI. The right/left lung perfusion ratio between 65:35 and 40:60 was considered as normal.
Results: The mean right/left lung perfusion ratio was 63:37, while the mean right/left pulmonary artery cross-sectional area ratio was 54:46 (P<0.05). Regurgitation fraction (RF) was significantly greater in the left pulmonary artery (LPA) (12.2±16.8%) than in the right pulmonary artery (RPA) (3.2±5.5%; P=0.014). There was no significant correlation between right/left pulmonary artery cross-sectional area ratio and the right/left lung perfusion ratio (R²=0.089, P=0.139). The large difference (>10%) between right/left pulmonary artery cross-sectional area ratio and the right/left lung perfusion ratio was found in 16 (61.5%) cases. Abnormal right/left lung perfusion ratio was observed in 10 (38.5%) of 26 patients. Central pulmonary arteries sizes predicted the asymmetry of lung perfusion only in 2 of 10 cases.
Conclusions: Morphological evaluation of the proximal branch pulmonary arteries cannot be used to predict differential perfusion of the lungs in patients with conotruncal heart defects. Asymmetric pulmonary perfusion is not related to the size of the proximal branch pulmonary arteries in most cases. The higher RF observed in the LPA compared with the RPA suggest that the pulmonary vascular resistance greatly dominates differential perfusion of the lungs over the anatomy of the central pulmonary arteries.