Noninvasive surrogate of main pulmonary artery stiffness is associated with right ventricular function in experimental pulmonary arterial hypertension.

Main pulmonary artery (MPA) stiffening increases right ventricular (RV) afterload and is associated with worse outcomes in pulmonary arterial hypertension (PAH). Measures of pulmonary artery compliance (PAC) and vascular resistance (PVR) require invasive catheterization, limiting clinical application. Echocardiographic assessment of MPA pulsatility, the relative change in MPA diameter, may be useful but not well validated. We investigated the relationship between MPA pulsatility and passive stiffness, PAC, PVR, RV function, and RV-PA coupling in sugen-hypoxia (SuHx) rats and children with idiopathic PAH (iPAH) and controls. Groups of 3-wk and 6-wk SuHx rats and controls underwent echocardiography and invasive catheterization to characterize progressive changes in MPA pulsatility, PAC, PVR, and RV function. Harvested MPAs underwent biaxial tensile testing to determine its passive stiffness. RV echo function and MPA pulsatility were retrospectively analyzed in patients with iPAH and healthy subjects. PAH rats and patients with iPAH had reduced MPA pulsatility [23 ± 7.9% at 3-wk and 18 ± 5.0% at 6-wk SuHx; 14.5(7.7) in iPAH] compared with controls [40 ± 7% at 3-wk and 31 ± 6% at 6-wk in healthy controls; 30.8(6.9) in healthy subjects]. Reduced MPA pulsatility correlated with increased high-strain circumferential passive stiffness (r = -0.88, P < 0.0001), reduced PAC (r = 0.78, P < 0.0001), increasing PVRi (r2 = 0.47, P < 0.0001), RV dysfunction, and impaired coupling in PAH rats. MPA pulsatility in iPAH and healthy subjects was inversely related to RV size and positively linearly related to RV systolic function. Our results suggest that MPA pulsatility is an accessible measure of MPA stiffness, expanding the assessment of RV afterload and RV-PA coupling in PAH. NEW & NOTEWORTHY Pulmonary artery compliance and stiffness are increasingly recognized as contributors to outcomes in pulmonary arterial hypertension (PAH). We report significant associations between main pulmonary artery (MPA) pulsatility and gold standard measures of MPA stiffness, components of right ventricular (RV) afterload, function, and RV-PA coupling in experimental and in patients with iPAH. Our findings suggest that MPA pulsatility is a simple, accessible surrogate to MPA stiffness that may facilitate the assessment of prognostically important factors in PAH.