Right ventricular end-diastolic stiffness heralds right ventricular failure in monocrotaline-induced pulmonary hypertension.

Recent studies suggest right ventricular (RV) stiffness is important in pulmonary hypertension (PH) prognosis. Smaller stroke volume (SV) variation after a certain RV end-diastolic pressure (EDP) respiratory variation as assessed by spectral transfer function (STF) may identify RV stiffness. Our aim was to evaluate RV stiffness in monocrotaline (MCT)-induced PH progression and to validate STF gain between EDP and SV as marker of stiffness. Seven-week-old male Wistar rats randomly injected with 60 mg/kg MCT or vehicle were divided into three groups (n = 12 each) according to cardiac index (CI): controls (Ctrl), preserved CI (MCT pCI), and reduced CI (MCT rCI). All underwent RV pressure-volume (PV) evaluation 24-34 days after MCT, under halogenate anesthesia and constant positive-pressure ventilation. End-diastolic stiffness (β), end-systolic elastance (Ees), arterial elastance for indexed volumes (Ea), and preload recruitable stroke work (PRSW) were obtained and beat-to-beat fluctuations during ventilation assessed by STF. Ea was the strongest determinant of CI, alongside β but not PRSW. MCT rCI showed impaired ventricular-vascular coupling (VVC) and higher β, along with low end-diastolic pressure (EDP) and stroke volume index (SV) STF gain, denoting impaired preload reserve. On multivariate analysis β and not Ees correlated with EDP-SV STF gain (P < 0.001). Receiver-operating characteristics (ROC) curve analysis of EDP-SV STF gain showed an area under curve of 0.84 for β prediction (P = 0.002). Afterload, impaired VVC and RV stiffness are major players in RV failure. RV stiffness can be assessed by STF gain analysis of respiratory fluctuations between EDP and SV, which may constitute a prognostic tool in PH.