A haemodynamic study of pulmonary hypertension in chronic hypersensitivity pneumonitis

Chronic hypersensitivity pneumonitis is a common fibrotic interstitial lung disease. The prevalence of pulmonary hypertension diagnosed by right heart catheterisation and its cardiopulmonary function findings in patients with chronic hypersensitivity pneumonitis are unknown. Consecutive symptomatic patients with chronic hypersensitivity pneumonitis were prospectively evaluated. All patients were submitted to right heart catheterisation, pulmonary function testing, a 6-min walk test, echocardiography, blood gas determination and N-terminal pro-brain natriuretic peptide analyses. Nonhypoxaemic patients also underwent incremental cardiopulmonary exercise testing. 50 patients underwent right heart catheterisation; 25 (50%) of these had pulmonary hypertension and 22 (44%) had a pre-capillary haemodynamic pattern. The patients with pre-capillary pulmonary hypertension had lower forced vital capacity (mean +/- SD 50 +/- 17% versus 69 +/- 22% predicted, p<0.01), carbon monoxide diffusing capacity (37 +/- 12% versus 47 +/- 14% predicted, p<0.01), arterial oxygen tension (median (interquartile range) 59.0 (47.8-69.3) versus 73.0 (62.2-78.5) mmHg, p<0.01) and saturation after the 6-min walk test (78 +/- 8% versus 86 +/- 7%, p<0.01). In pre-capillary pulmonary hypertension, oxygen uptake was also lower at the anaerobic threshold (41 +/- 11% versus 50 +/- 8% predicted, p=0.04) and at peak exercise (12.8 +/- 1.6 versus 15.0 +/- 2.5 mL.kg(-1).min(-1), p=0.02). Pre-capillary pulmonary hypertension is common in symptomatic chronic hypersensitivity pneumonitis and is related to interstitial lung disease severity. Additionally, pulmonary hypertension is more prevalent in hypoxaemic patients with impaired lung function and exercise capacity.