Abstract 14221: Right Ventricular Adaptation to Pressure Overload: Differences Between Chronic Thromboembolic Pulmonary Hypertension and Idiopathic Pulmonary Arterial Hypertension

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) and idiopathic pulmonary arterial hypertension (iPAH)) are both associated with right ventricular (RV) failure and death. Although both conditions develop in the pre-capillary pulmonary vasculature, patient characteristics are different. CTEPH patients are older, predominantly male and more often have a history of venous thromboembolism. Therefore, the RV might be affected differently in CTEPH compared to iPAH. We aimed to compare RV adaptation in CTEPH and iPAH. Methods: Between 2000 and 2019 all treatment naive iPAH and CTEPH patients diagnosed in the Amsterdam UMC were included if a right heart catheterization and cardiac magnetic resonance imaging (CMR) were performed at the time of diagnosis. RV volumes, mass and function were assessed with CMR. RV contractility, afterload, RV-pulmonary artery (RV-PA) coupling and diastolic stiffness (Eed) were obtained using single beat pressure-volume loop analysis. Differences in RV phenotypes between iPAH and CTEPH were analyzed using multiple linear regression with interaction testing after correcting for confounders. Results: A total of 235 patients were included, 116 with CTEPH and 119 with iPAH. CTEPH patients were older, predominantly male, had a higher systemic blood pressure and a lower pulmonary vascular resistance at the time of diagnosis. After correcting for these confounders, RV function and RV-PA coupling were similar in both groups. However, CTEPH patients had a higher RV end-diastolic volume index (87±27 ml/m2 vs. 82±25 ml/m2), and a lower RV wall thickness (0,6±0,1 g/ml vs. 0,7±0,2 g/ml; figure 1A). The increase in afterload in CTEPH was associated with a disproportionally larger increase in diastolic stiffness compared to iPAH, independent of RV wall thickness (figure 1B). Conclusions: Despite a similar RV function, the RV in CTEPH is more dilated and stiffer than the RV in iPAH, independent of age, sex and afterload.