Microvascular dysfunction in chronic kidney disease: A feasibility study.

BACKGROUND: Microvascular dysfunction contributes to PAD progression, and its detection may facilitate earlier recognition and risk stratification. People with advanced chronic kidney disease (CKD) have a high burden of PAD, yet early detection is limited by disease-related changes, such as medial calcification. Near-infrared spectroscopy (NIRS) is a candidate microvascular tool for early PAD detection, but its feasibility in CKD is unknown. PURPOSE: To evaluate NIRS feasibility for assessing lower limb microvascular function in participants with CKD Stage 5 (dialysis and non-dialysis) versus controls. METHODS: Using an ischaemic challenge, lower limb reperfusion kinetics of the tibialis anterior were assessed by NIRS in CKD participants and controls. Feasibility was defined as acceptability, technical limitations, interpretability, and safety; a priori analyses examined associations between participant characteristics and feasibility within CKD. NIRS indices were compared with brachial and popliteal hyperaemic velocity-time integral (VTI). RESULTS: Thirty-eight CKD and 20 controls were included. Among CKD participants, 79% of tests were acceptable versus 100% of controls, linked to higher ankle systolic blood pressure and BMI. Interpretability was reduced in 39% of CKD tests, unrelated to these characteristics. Popliteal VTI correlated moderately with NIRS reperfusion time from nadir to baseline (r = -0.64) and hyperemic AUC (r = 0.63); brachial VTI did not. CONCLUSIONS: NIRS was feasible when tolerated, but acceptability and interpretability limited its use in advanced CKD. Acceptability, but not interpretability, was limited by markers of vascular severity consistent with a calcified, poorly compressible vasculature. Moderate correlations with popliteal VTI support the potential utility of NIRS in this population.