Cardiac magnetic resonance imaging-derived pulmonary artery distensibility index correlates with pulmonary artery stiffness and predicts functional capacity in patients with pulmonary arterial hypertension

Background: Increased stiffness of the pulmonary vascular bed is known to increase mortality in patients with pulmonary arterial hypertension (PAH); and pulmonary artery (PA) stiffness is also thought to be associated with exercise capacity. The purpose of the present study was to investigate whether cardiac magnetic resonance imaging (CMRI)-derived PA distensibility index correlates with PA stiffness estimated on right heart catheterization (RHC) and predicts functional capacity (FC) in patients with PAH. Methods and Results: Thirty-five consecutive PAH patients (23% male, mean age, 44±13 years; 69% idiopathic) underwent CMRI, RHC, and 6-min walk test (6MWT). PA distensibility indices were derived from cross-sectional area change (%) in the transverse view, perpendicular to the axis of the main PA, on CMRI [(maximum area-minimum area)/minimum area during cardiac cycle]. Among the PA stiffness indices, pulmonary vascular resistance (PVR) and PA capacitance were calculated using hemodynamic dataset from RHC. CMRI-derived PA distensibility was inversely correlated with PVR (R ²=0.34, P<0.001) and directly correlated with PA capacitance (R ²=0.35, P<0.001), and the distance in the 6MWT (R ²=0.61, P<0.001). Furthermore, PA distensibility <20% predicted poor FC (<400 m in 6MWT) with a sensitivity of 82% and a specificity of 94%. Conclusions: Non-invasive CMRI-derived PA distensibility index correlates with PA stiffness and can predict FC in patients with PAH.