# Pulmonary function impairment and its relationship with target therapy response in patients with pulmonary arterial hypertension

## TL;DR

This study shows that lung function issues in pulmonary arterial hypertension patients are linked to how well they respond to treatment.

## Contribution

The study identifies a specific lung function threshold (FVC% pred < 82%) that predicts poor response to PAH-targeted therapy.

## Key findings

- PAH patients show reduced ventilation and diffusion capacity in pulmonary function tests.
- FVC and FEV1 are positively correlated with 6-minute walking distance in PAH patients.
- Patients with FVC% pred below 82% have significantly diminished response to PAH-targeted therapy.

## Abstract

Patients with pulmonary arterial hypertension (PAH) exhibit exertional dyspnea and decreased exercise capacity, which are not solely attributable to right heart dysfunction. Numerous studies have aimed to elucidate pulmonary function in PH patients and its correlation with disease severity and prognosis; however, the findings remain inconsistent. The impairment of ventilation and diffusion function may partially account for the occurrence of exertional dyspnea in PAH patients.

This was a single-center prospective observational study. Pulmonary function tests, right heart catheterization, and four-strata risk status stratification were performed in PAH patients. The PAH patients were followed up for 12 months.

A total of 181 PAH patients were enrolled in the study, comprising 62 with idiopathic pulmonary arterial hypertension (IPAH) and heritable PAH (HPAH), 69 with PAH associated with congenital heart disease (CHD-PAH), and 50 with PAH associated with connective tissue disease (CTD-PAH). Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), single-breath diffusion capacity for carbon monoxide (DLCO), DLCO% predicted (% pred), and reactance at 5 Hz (X5) were significantly reduced, while residual volume (RV)% pred increased in PAH patients. CHD-PAH exhibited more pronounced ventilation impairment. Six-minute walking distance (6MWD) demonstrated a positive correlation with FEV1 (r = 0.353, p < 0.01) and FVC (r = 0.373, p < 0.01), respectively. A total of 104 patients finished the follow-up. Patients exhibiting FVC% pred values below 82% demonstrated a diminished response to PAH-targeted therapy (OR = 10.553, p = 0.000, 95% CI: 2.580–43.165).

PAH patients exhibited impairment in both ventilation and diffusion capacity, while patients with diverse etiologies demonstrated distinct characteristics. FVC and FEV1 were positively correlated with 6MWD, respectively. PAH patients with FVC% pred values below 82% demonstrated a diminished response to PAH-targeted therapy.