Association between endothelial function and microvascular changes in patients with secondary Raynaud’s phenomenon

Nailfold capillaroscopy (NC) represents the method to analyze microvascular abnormalities in autoimmune rheumatic diseases, but the pathophysiological link between the microvascular derangement which is seen in NC and endothelial function is yet to be discovered. We investigated the association between endothelial function and microvascular derangement in patients with Raynaud’s phenomenon (RP). Postmenopausal women (n = 37) with secondary RP and age-matched healthy controls (n = 25) were evaluated with NC. Microvascular alterations were assessed by microangiopathy evolution score. Endothelial function was examined by brachial artery flow-mediated dilatation (reactive FMD, endothelium-dependent) and response to 40 μg of sublingual nitroglycerine (NTG-induced dilatation, endothelium-independent). There was significant capillary loop dilatation (apical width; 14.1 ± 5.6 vs. 10.4 ± 1.7 μm, p = 0.001 and total width; 40.6 ± 15.1 vs. 31.6 ± 4.6 μm, p = 0.002) and lengthening (316.0 ± 78.5 vs. 270.4 ± 34.7 μm, p = 0.004) in secondary RP compared to controls. Additionally, giant capillaries, loss of capillaries, hemorrhage, and background pallor were much more prevalent in secondary RP as compared to controls (all p’s < 0.05). Although there were no significant differences in NTG-induced dilatation between secondary RP and controls (16.1 ± 5.9 vs. 19.6 ± 9.0 %, p = 0.091), significant decreases in the reactive FMD value (6.1 ± 3.5 vs. 9.0 ± 2.2 %, p = 0.001) were noted. Both FMD and NTG-induced dilatation showed a significant inverse association with microangiopathy evolution score (r = −0.355, p = 0.005 and r = −0.285, p = 0.028). Significantly impaired endothelial function was found in secondary RP, and microvascular derangement was associated with endothelial dysfunction.