CAPILLARY DENSITY DURING POSTOCCLUSIVE REACTIVE HYPEREMIA AND VENOUS CONGESTION DETERIORATES WITH ADVANCING CKD STAGES

Abstract

Objective: Cardiovascular disease is the main cause of mortality in CKD patients. Endothelial dysfunction and capillary rarefaction are established cardiovascular risk factors. Nailfold video-capillaroscory provides a thorough assessment of capillary density and microcirculation changes. The aim of this study is to examine structural and functional capillary density in CKD patients of stages 2 to 4. Design and method: A total of 96 CKD patients were included in the study. The population consisted of 4 equal groups according to CKD stage (2, 3a, 3b and 4). All patients underwent nailfold video-capillaroscopy, during which capillary density was measured at baseline, after a 4-minute arterial occlusion (postocclusive reactive hyperemia) and at the end of a 2-minute venous occlusion (congestion phase). Arterial stiffness and arterial wave parameters were measured with applanation tonometry and common carotid intima-media thickness (IMT) with a 2D ultrasound device. Results: Capillary density at baseline showed a progressive reduction with advancing CKD stages (stage 2: 32.63 ± 2.79, stage 3a: 31.23 ± 3.84, stage 3b: 32.48 ± 3.34, stage 4: 28.50 ± 3.09, p < 0.001). Similar reductions were observed in capillary density during postocclusive hyperemia (39.42 ± 3.00, 37.63 ± 4.24, 38.35 ± 3.83, and 33.77 ± 3.34, respectively, p < 0.001) and after venous congestion (41.10 ± 3.09, 39.02 ± 4.41, 39.90 ± 3.51, and 35.21 ± 3.40, p < 0.001). Office pulse wave velocity showed a non-significant increasing trend with advancing CKD, but carotid IMT did not. In multivariate regression analysis, eGFR showed a positive association (per ml/min increase; OR: 0.053, 95%CI: 0.004 to 0.101), whereas diabetes (OR: -1.706, 95%CI: -3.176 to -0.236), and parathormone (PTH) (per pg/ml increase; OR: -0.022, 95%CI: -0.036 to -0.008) negative associations with post-occlusive capillary density. Conclusions: Both structural and functional capillary density progressively decrease with advancing CKD stages. Apart from reduced eGFR, the presence of diabetes and increased PTH levels are independently associated with this reduction. This capillary rarefaction may play a central role in the increased burden of cardiovascular events in CKD patients.