Pulmonary arterial stiffness and vascular tone in pulmonary hypertension: Insights from waveform-derived reflection index and hemodynamic correlations.

Background: Pulmonary hypertension (PH) involves increased arterial stiffness and reduced vascular tone, affecting pulmonary arterial wave reflections. The Reflection Index (RI) may provide insights into these changes.

Objective: This study examines the utility of RI in PH patients by correlating it with key right heart catheterization (RHC) parameters.

Methods: Patients who underwent RHC with a preliminary diagnosis of PH, including those with normal RHC findings and those diagnosed with Group 1 and Group 4 PH, were included in the study. RI was defined as the ratio of systolic to diastolic pressure differences from pulmonary arterial waveforms and compared with hemodynamic, clinical, and echocardiographic parameters.

Results: The study included 115 patients (mean age 53.92 ± 16.43 years; 43.5% male). RI showed significant correlations with key RHC parameters, such as sPAP (r=0.359, p<0.001), dPAP (r=0.322, p<0.001), mPAP (r=0.339, p<0.001), PVR (r=0.431, p<0.001), and pSO2 (r=-0.243, p=0.011). Among echocardiographic measures, RI correlated with TRV (r=0.377, p<0.001) and echo sPAP (r=0.359, p<0.001). In multivariable analysis, RI (OR:1.032, p=0.003) and NT-proBNP (OR:1.004, p=0.049) remained significant predictors of PH. ROC analysis demonstrated the moderate predictive power for RI (AUC=0.806, p<0.001), with 76.4% sensitivity and 78.5% specificity at a cut-off of 232.05.

Conclusion: RI is a valuable parameter for assessing pulmonary arterial stiffness and vascular tone in patients with PAH and CTEPH. Significant correlations were observed with key hemodynamic parameters, including PVR and mPAP. Additionally, RI demonstrated moderate predictive power for PH. These findings highlight the potential of RI as an independent marker of vascular health, providing direct insights into the pulmonary arterial bed.