Clinical relevance of microvascular endothelial dysfunction in idiopathic pulmonary fibrosis

Endothelial dysfunction (ED) is involved in the pathophysiology of idiopathic pulmonary fibrosis (IPF). Reactive hyperaemia peripheral arterial tonometry (RH-PAT) is a rapid, reproducible, noninvasive technique for assessing peripheral microvascular endothelial function.

We conducted a prospective study of endothelial function (reactive hyperaemia index (RHI) as measured by RH-PAT) in patients with IPF, in order to explore the association between ED and respiratory symptoms, lung function and the disease prognosis. Adult patients with IPF underwent a baseline assessment of respiratory symptoms (including dyspnoea on the modified Medical Research Council scale), blood gas levels, pulmonary function tests, a 6-min walk test (6MWT) and endothelial function. The same examinations were performed 12, 24 and 36 months after inclusion.

42 patients with IPF (men: 76%) were enrolled. The median (IQR) age was 70 (61-75) years. The median (IQR) forced vital capacity and diffusing capacity of the lung for carbon monoxide (D _LCO) were 77% (66-93%) and 43% (33-53%) predicted, respectively. The median (IQR) RHI was 1.86 (1.60-2.48). An ED defined at the RHI reference cut-off of 1.67 was observed in 13 (31%) patients. After 1 year of follow-up, there was a significant decline in endothelial function (median (IQR) difference: 0.65 (0.35-0.85), p=0.009). The RHI was associated with dyspnoea (r= -0.33, p=0.036), D _LCO (r=0.36, p=0.025) and oxygen saturation at the end of 6MWT (r=0.33, p=0.049). The subgroups of patients with and without ED did not differ significantly in terms of mortality or the occurrence of acute exacerbations, although there was a nonsignificant trend to greater functional disease progression in patients with ED.

Finger ED was correlated with respiratory symptoms and functional variables and worsened during the first year of follow-up. Our results suggest that the severity of IPF is associated with ED, although further studies are needed to assess the value of RH-PAT in the management of IPF.