Arterial load and right ventricular-vascular coupling in pulmonary hypertension

Right ventricular (RV) functional adaptation to afterload determines outcome in pulmonary hypertension (PH). RV afterload is determined by the dynamic interaction between pulmonary vascular resistance (PVR), characteristic impedance (Zc), and wave reflection. Pulmonary vascular impedance (PVZ) represents the most comprehensive measure of RV afterload; however, there is an unmet need for an easier bedside measurement of this complex variable. Although a recent study showed that Zc and wave reflection can be estimated from RV pressure waveform analysis and cardiac output, this has not been validated. Estimations of Zc and wave reflection coefficient (λ) were validated relative to conventional spectral analysis in an animal model. Zc, k, and the single-beat ratio of end-systolic to arterial elastance (Ees/Ea) to estimate RV-pulmonary arterial (PA) coupling were determined from right heart catheterization (RHC) data. The study included 30 pulmonary artery hypertension (PAH) and 40 heart failure with preserved ejection fraction (HFpEF) patients [20 combined pre- and postcapillary PH (Cpc-PH) and 20 isolated postcapillary PH, (Ipc-PH)]. Also included were 10 age- and sex-matched controls. There was good agreement with minimal bias between estimated and spectral analysis-derived Zc and k. Zc in PAH and Cpc-PH groups exceeded that in the Ipc-PH group and controls. k was increased in Ipc-PH (0.84 ± 0.02), Cpc-PH (0.87 ± 0.05), and PAH groups (0.85 ± 0.04) compared with controls (0.79 ± 0.03); all P values were