Feasibility of high-resolution flow-mediated dilation using a 24-MHz probe to assess endothelial dysfunction: comparison of hypertensive and normotensive groups.

This study investigated differences in endothelial cell dysfunction (ECD) and vascular response between hypertensive (HT) and non-hypertensive (NHT) individuals, as evaluated by high-resolution flow-mediated dilation (hrFMD) using a 24-MHz ultrasound probe. The study included 31 participants in the HT group and 29 in the NHT group. Clinical data, laboratory findings, and carotid intima-media thickness (cIMT) were measured, as were brachial artery systolic and diastolic diameters at baseline and 30, 60, and 120 seconds after a 5-minute cuff occlusion. Based on these measurements, systolic (TERS) and diastolic (TERD) traditional expansion ratios (TER), as well as a new expansion ratio (NER), were calculated for each post-occlusion time point. Differences, correlations, and multivariable logistic regression analyses were used to evaluate associations between ECD and hrFMD indices, with odds ratios (ORs) and 95% confidence intervals (CIs) reported. At 60 seconds, NER and TER values in the HT group were significantly lower than in the NHT group. Most participants in the NHT (22/29, 75.8%) and HT (21/31, 67.7%) groups exhibited peak vasodilation at NER₆₀. NER₆₀ was negatively correlated with age (r=-0.603, P<0.001), cIMT (r=-0.328, P=0.011), and systolic blood pressure (r=-0.277, P=0.032). NER₆₀ was associated with hypertension-related ECD independently of major cardiovascular risk factors (OR, 0.025; 95% CI, 0.002 to 0.316; P=0.004). In hrFMD, NER₆₀ was significantly lower in HT than in NHT participants and may represent a surrogate marker for impaired vascular reactivity associated with hypertension. However, its role in the direct detection of ECD requires further validation against established physiological criteria.