Abstract Body (Do not enter title and authors here): Background: Right heart adaptation to emerging pulmonary arterial hypertension (PAH) largely determines outcomes. While numerous studies focus on ventricular remodeling, few explore the contribution of pulmonary artery (PA) stiffness indices across PAH subtypes.
Research Questions and Aims: We assessed PA distensibility (PAD) in systemic sclerosis (SSc) patients with and without PAH compared with idiopathic pulmonary arterial hypertension (IPAH) using cardiac magnetic resonance imaging (CMR) and transthoracic echocardiography (TTE). We also assessed the intermodality agreement in PAD assessment.
Methods: We included SSc and IPAH patients who underwent right heart catheterization (RHC), CMR, and TTE. PAD was calculated using CMR transaxial PA images and TTE parasternal short-axis PA view with measurement of systolic and diastolic diameters. The areas corresponding to these diameters were derived using the formula for the area of a circle (πr²). PAD was computed as PA pulsatility over pulse pressure, with PA pulsatility being the percentage change in PA cross-sectional area between systole and diastole.
Results: Of 45 SSc patients (34 with PAH, 11 without) and 16 IPAH patients, 46 had adequate image quality. Mean PA pressure by RHC was notably higher in IPAH cases than in those with SSc-PAH. PAD and PA pulsatility were lowest in the SSc-PAH group, followed by IPAH, and highest in the SSc without PAH group (p<0.001). In PAH, PA pulsatility differed between SSc-PAH and IPAH. Figure 1 demonstrates a strong positive correlation (R=0.965) and substantial intermodality consistency (CCC=0.942). Agreement was stronger at lower values, with increased dispersion at higher values. Over 60 months, intermodality metrics of PAD and PA pulsatility predicted mortality. Kaplan-Meier analysis revealed that PA pulsatility greater than 10.5% significantly predicts better survival than less than 10.5%.
Conclusion: We found diminished PAD in SSc-PAH than IPAH, despite lower PA pressures, predictive of mortality. We also demonstrate intermodality agreement supporting that TTE may be an alternative to CMR for assessing PAD.