Determinants Of Right Ventricular Diastolic Stiffness In Precapillary Pulmonary Hypertension: A Cardiac Magnetic Resonance Study

Background: In precapillary pulmonary hypertension (PH), the causal relationships between right ventricular (RV) diastolic stiffness and RV fibrosis or hypertrophy are not well established. Aim: to investigate whether RV diastolic stiffness could be attributed to RV fibrosis and hypertrophy in patients with precapillary PH. Methods: This is a retrospective study of 31 patients with pulmonary arterial hypertension (PAH) and 32 patients with chronic thromboembolic pulmonary hypertension (CTEPH). All patients underwent cardiac magnetic resonance imaging (CMRI) and right heart catheterization (RHC) within 30 days interval. Single-beat pressure-volume analysis was used for the calculation of RV end-diastolic elastance (stiffness, Eed). Using dedicated software (Med-suite), RV mass and native T1-mapping values at the RV lateral wall and interventricular insertion points (IVIPs) were traced. Results: Mean age was 54 years and 54% were females. Median Eed was 0.48 (IQR 0.22-0.70) mmHg·mL-1 without significant difference between both PH phenotypes (P=0.11). Univariate and multivariate analyses were performed to examine the associations between Eed and CMR as well as RHC derived variables, which revealed four independent determinants of higher Eed including RV mass index, mean pulmonary artery pressure, pulmonary vascular resistance, and cardiac output (β= 1.19, 1.27, 0.99 & -0.14; P= <0.01, 0.02, 0.03 & 0.02, respectively). Conclusion: RV diastolic stiffness is associated with RV hypertrophy, hemodynamics, and cardiac output but not with CMR derived RV fibrosis. Larger studies are needed to confirm the association between RV diastolic stiffness and RV fibrosis.