Right Ventricular Afterload Across the Pulmonary Hypertension Spectrum

Right ventricular (RV) performance is the major determinant in pulmonary hypertension (PH). RV afterload is typically assessed using pulmonary vascular resistance (PVR) and pulmonary arterial (PA) compliance, overlooking the dynamic component of pulsatile load. Characteristic impedance serves as a measurement of the opposition to pulsatile flow in the proximal arteries. Combined post- and precapillary PH (CpcPH) represents a growing and therapeutically challenging subgroup whose hemodynamic profile remains incompletely characterized. Our aim was to comprehensively describe RV afterload components across the PH spectrum and to evaluate their associations with RV morphology and function. We applied the time-domain method reported in literature to calculate characteristic impedance in a prospective cohort of 78 patients with PH undergoing right heart catheterization and cardiac magnetic resonance. PVR, PA compliance, and characteristic impedance were assessed and compared across precapillary PH (PAH and CTEPH), isolated post-capillary PH (IpcPH), or CpcPH. IpcPH exhibited higher compliance (2.3 mL/mmHg [1.9-3.4]) and lower impedance and PVR (84.5 [63.8-112.2] and 186.0 dyn.s.cm-5 [139.4-208.0] respectively). CpcPH showed intermediate values (1.8 mL/mmHg [1.0-2.7]; 120.4 [88.3-177.7] and 384.8 dyn.s.cm-5 [257.5-627.9]) between IpcPH and precapillary PH (1.4 mL/mmHg [1.1-2.1], 182.5 [123.4-231.4] and 524.1 [367.9-714.5] dyn.s.cm-5), with values closer to the precapillary end of the spectrum. We concluded that CpcPH occupies an intermediate hemodynamic phenotype within the PH spectrum, with some patients showing substantial overlap in afterload components with PAH and CTEPH patients. We observed that characteristic impedance provided complementary information on RV afterload beyond conventional metrics, supporting its integration into multimodal hemodynamic assessment.