Empiric Pulmonary Arterial Compliance Reflects the Resistance-Compliance Relationship and Predicts Mortality in Pulmonary Hypertension.

The resistance-compliance (RC) relationship between pulmonary vascular resistance (PVR) and pulmonary arterial compliance (PAC) provides an integrative measure of global right ventricular (RV) afterload. However, debate persists regarding the clinical utility of PAC calculated using the empiric formula (PACempiric), and the ideal method for calculating PAC. We analysed haemodynamic and pulmonary pressure waveform data from 156 patients with pulmonary hypertension (PH). PAC was calculated using three methods: PACempiric, as well as two established waveform analysis methods, area-under-the-curve (PACAUC), and diastolic decay (PACDD). Generalized linear mixed models were used to evaluate the relationship between PVR and PAC across these three methods. Model performance was assessed using Akaike and Bayesian Information Criteria (AIC/BIC). The diagnostic performance of each method was evaluated using ROC analysis. Cox regression was applied to assess the association with long term mortality. All three PAC methods demonstrated a strong inverse hyperbolic correlation with PVR. PACempiric provided stronger model performance (AIC -504.3; R² = 0.968), and best discriminated PH subtypes (AUC = 0.91), outperforming PACAUC (AUC = 0.88) and PACDD (AUC = 0.75). PACempiric was also a stronger predictor of mortality than PACAUC, PACDD or PVR (c-statistic = 0.747, compared to 0.737, 0.709 and 0.741 respectively). PACempiric is a robust and accessible method for assessing the pulsatile component of RV loading. This study supports its use as a physiologically meaningful parameter that together with PVR provides a comprehensive estimation of global RV afterload.