Pulmonary artery growth in univentricular physiology patients

A Fontan-type operation, i.e. a connection of the systemic veins and pulmonary arteries without subpulmonary ventricle, with different surgical techniques, is nowadays the only treatment option for patients with a functionally univentricular heart (UVH). Understanding the development of pulmonary arteries in patients who are considered for the Fontan procedure is important clinically.

To evaluate the development of pulmonary arteries in patients with univentricular circulation.

Between 1995 and 2007, 111 patients underwent a bidirectional Glenn procedure. In all patients, preoperative catheterisation was performed to assess the anatomy and haemodynamics of UVH, especially the size of the pulmonary arteries. Ninety nine patients were included in the bidirectional Glenn group; 62 of these underwent repeat catheterisation before Fontan completion. The late results, after one stage extracardiac total cavopulmonary anastomosis performed in 24 patients between 1992 and 2002, were reinvestigated (one-stage Fontan group). We assessed the changes in the McGoon ratio and Nakata index for the whole cohort of patients. McGoon ratio is the sum of the diameter of pulmonary arteries divided by the diameter of the aorta. Nakata index is the sum of the cross-sectional area of the pulmonary arteries divided by the body surface area.

During cardiac catheterisation prior to Glenn procedure, the mean Nakata index was 351.9 (range 131.2-886) mm2/m2 and was higher in patients with increased pulmonary flow (p = 0.0135). Mean McGoon ratio was 2.5 (range 1.1-4.9). An average 40.3 months after Glenn procedure, the Nakata index and McGoon ratio decreased significantly to 226.4 ± 125 mm²/m² (p < 0.003), and to 2.14 ± 0.58 (p < 0.008) respectively. In the group of patients after one-stage Fontan in late follow-up, mean 7.4 years after procedure, the Nakata index decreased from 318.7 ± 159.1 mm²/m² to 120 ± 40 mm²/m² (p < 0.0001) and McGoon ratio from 2.4 ± 0.6 to 1.4 ± 0.27 (p < 0.0001). Only size of pulmonary arteries before Glenn procedure, in the bidirectional Glenn group, or before Fontan operation, in the one-stage Fontan group,were inversely correlated with the changes of size of pulmonary arteries (p = 0.0015 and p = 0.0012).

The relative decrease of the size of pulmonary arteries in the inter-stage period (between bidirectional Glenn anastomosis and Fontan completion) and after Fontan completion may indicate that pulmonary artery sizes should probably not bean absolute limiting factor in the decision on treatment of functionally UVH patients, especially at the stage of Fontan approach.