Pulmonary arterial stiffness as the main correlate of effective arterial elastance in pre- and post-capillary pulmonary hypertension

Background

A simplified estimate of pulmonary effective arterial elastance (Ea_sPAP), defined as systolic pulmonary artery (PA) pressure divided by stroke volume (SV), is increasingly used to quantify total PA load and its coupling with right ventricle in pulmonary hypertension (PH), with elevated Ea_sPAP associated with worse prognosis. Although arterial elastance is thought to depend more on pulmonary vascular resistance (PVR) than on stiffness, the value of this simplified, clinically derived estimate remains unclear.

Methods

This retrospective invasive study included 236 adults diagnosed with idiopathic pulmonary arterial hypertension (n = 118) or post-capillary PH (n = 118), matched for age, sex, and mean PA pressure (mPAP). Total PA stiffness was defined as PA pulse pressure/SV.

Results

In the overall population (63 % women, median age 70 years, mPAP 38 mmHg), Ea_sPAP correlated most strongly with stiffness (Spearman ρ=0.95). The same was observed in both groups, with regression lines showing similar slopes and intercepts. These correlations were explained by the superimposable linear relationships between systolic and pulse pressures, together with the shared SV in the formulas. Ea_sPAP was less strongly associated with PVR (ρ=0.83) (P < 0.0001), with differing slopes and intercepts between groups. Similar results were observed when downstream pressure was included in elastance calculation, and in the youngest age tertile.

Conclusions

In PH patients, Ea_sPAP most closely correlated with the PA pulse pressure/SV ratio, the standard clinical estimate of total PA stiffness. This overlap among clinical indices of PA load warrants recognition, suggesting right ventricular responses may be mainly driven by pulsatile load, with potential therapeutic implications.