Dilatation of the main pulmonary artery in patients with isolated pulmonary stenosis: Arteriopathy or hemodynamic consequence?

Background: Main pulmonary artery (mPA) dilatation has been reported in patients with isolated pulmonary valve (PV) stenosis. The aim of our study was to detect the incidence of mPA dilatation and aneurysm in patients with isolated PV stenosis and the association with PV function.

Methods: In this single-centre retrospective observational study all patients with a diagnosis of isolated PV stenosis referred to our centre were enrolled. Patients were divided into two groups (children and adults) according to age. Echocardiography, cardiac magnetic resonance imaging (MRI) and computed tomography (CT) were reviewed. MPA dilatation was defined as ≥2 Z-Score in children and ≥30mm diameters in adults, while giant (aneurysmal) mPA dilatation was defined as ≥4 Z-Score in children and ≥40mm in adults.

Results: Out of 197 patients (41.6% males, 51.8% children), 67.2% presented mPA dilatation and 16.8% giant dilatation of the mPA. The majority were adults (p<0.001). There was an underestimation of the mPA with echocardiography in 11% of patients with mPA dilatation and 50% with giant mPA. The diameter did not correlate with sex and the degree of PV stenosis. About 44% of cohort under follow-up presented a progression in mPA dilatation, however no rupture or cardiac-related death was reported.

Conclusions: There is a very high incidence of mPA dilatation in both adults and paediatric patients with isolated PV stenosis. Nevertheless, there were not recorded dissections even in patients with the largest diameters suggesting a more benign lesion. Echocardiography often underestimates the mPA measurement compared to MRI/CT which might be indicated in selected patients as a baseline 3D cross-sectional imaging evaluation, even in the presence of mild PV disease, especially when the mPA is not well visualised.