# The resistance‐compliance relationship at low pulmonary resistance: Integrating pulmonary wedge pressure into right ventricular load assessment

## TL;DR

This paper explores how pulmonary capillary wedge pressure affects the relationship between pulmonary vascular resistance and compliance in patients with pulmonary hypertension, particularly in those with low resistance.

## Contribution

The study introduces a novel integration of pulmonary capillary wedge pressure into pulmonary arterial compliance calculations to better assess right ventricular afterload.

## Key findings

- The inverse PVR-PAC relationship was preserved across PH subgroups but modulated by PCWP in low PVR states.
- Adjusting PAC calculations for PCWP significantly improved model fit (R² increased from 0.725 to 0.919).
- In isolated post-capillary PH, the PVR-PAC relationship became statistically significant after PCWP adjustment.

## Abstract

The inverse hyperbolic relationship between pulmonary vascular resistance (PVR) and pulmonary arterial compliance (PAC) is a well‐established marker of right ventricular (RV) afterload. Pulmonary capillary wedge pressure (PCWP) is a known modifier of this relationship; however, its impact across pulmonary hypertension (PH) subgroups has not been well characterized. How does PCWP influence the resistance‐compliance (RC) relationship in PH subgroups, and can it be integrated into PAC calculations? Data from routine right heart catheterizations were analyzed to evaluate the PVR‐PAC relationship across PH subgroups, both with and without PCWP adjustment. The inverse PVR‐PAC relationship was apparent in cohorts with low PVR (p < 0.001). In isolated post‐capillary PH (Ipc‐PH), this relationship was PCWP‐dependent (unadjusted: p = 0.084; adjusted: p = 0.008). Incorporating PCWP significantly improved model fit (R
2 from 0.725 to 0.919). The RC relationship is broadly preserved across PH but is modulated by PCWP in low PVR states, particularly Ipc‐PH. Adjusting PAC calculations for PCWP may enhance the clinical assessment of RV afterload using this metric.