P171: Compliance of Extremely Dilated Main Pulmonary Arteries in Pulmonary Arterial Hypertension

Abstract

Background

Main pulmonary artery (MPA) dilation is a radiological sign of pulmonary hypertension (PH) and is an independent risk factor of sudden death (Żyłkowska et al, Chest 2012). Extreme MPA dilation is a rare consequence of PH. We hypothesize that the main pulmonary artery compliance is larger and contributes more to total arterial compliance in PH patients with an extremely dilated MPA when compared to patients with a less dilated MPA.

Methods

Cardiac magnetic imaging (CMR) scans of idiopathic and hereditary pulmonary arterial hypertension (PAH) patients were retrospectively analyzed. Six PAH patients with extremely dilated MPAs (≥45 mm diameter on transverse plain CMR images of the MPA) and six PAH patients with MPA diameter <45 mm were included. Total pulmonary arterial compliance (C_tot) was calculated by stroke volume (SV) over pulse pressure (PP) and MPA compliance (C_MPA) by (Δarea*length)/PP (length was assumed 5 cm for all MPAs). C_MPA/C_tot ratio could therefore be calculated by CMR derived flow images alone: C_MPA/C_tot = (Δarea*length)/SV.

Results

Mean age in both groups was not different, mean pulmonary artery pressure was higher in patients with an extremely dilated MPA (73 ± 9.0 mmHg) compared to patients with non-extremely dilated MPA (48 ± 5.4 mmHg, p = 0.02). A trend toward a higher C_MPA/C_tot ratio was observed in patients with extremely dilated MPA (p = 0.0534).

Conclusion

In PAH the contribution of the MPA to total compliance tends to be higher in patients with a MPA diameter ≥45 mm then in patients with a diameter <45mm.