Is the microvasculature tone increasing with arterial hypertension?

Abstract

Rationale: An increase in vascular tone is believed to be a major factor leading to arterial hypertension (AH). There are no means for a direct measurement of the vascular tone in clinical practice. Perfusion assessment by laser Doppler flowmetry (LDF) allows for an indirect evaluation of the vascular tone of the microcirculation system. Perfusion is assessed by the change in blood flow per unit of time in the given area. Therefore, this parameter should be inversely correlated with vascular tone. Aim: To compare the forearm skin perfusion measured by LDF in patients with AH and healthy volunteers with normal blood pressure, and to review the feasibility of this parameter for the assessment of the microvasculature tone.Materials and methods: The study was carried out in two groups: group one, patients with AH (n = 43; age 62 [57; 71] years), and group 2, healthy volunteers without AH (n = 62; age 28 [24; 37] years). The perfusion in the forearm skin was measured by LDF for 2 minutes without any functional tests. "Baseline perfusion” for each subject was calculated as the average perfusion rate in a representative portion of the microcirculatory curve.Results: Median of basic perfusion in the forearm skin in the patients with AH is significantly higher than that in the normotensive individuals: 4.88 [2.87; 8.98] PU and 3.41 [2.47; 4.99] PU, respectively (p = 0.013). The interquartile range of the baseline perfusion in the control group was chosen as provisional threshold values for the "normal” perfusion level. In 39.5% of patients with AH, their basic perfusion was within the "normal level”; 46.5% of the patients had the baseline perfusion above the "normal level”, which might be due to reduced tone of the peripheral vessels. Only 14.0% of the patients had a decreased level of the basic perfusion.Conclusion: An increase in the skin perfusion in some patients with AH may indicate a decrease in their peripheral vascular tone, which could be a potential compensatory reaction in response to the rise in blood pressure. The results obtained could have been influenced by the age-related changes in the cardiovascular system, drug therapy, etc. Further studies into the specifics of peripheral vasculature seem reasonable. They can contribute to the understanding of the pathophysiology of AH in a given patient and, in future, could be used to guide a personalized choice of therapy.

Keywords

• microcirculation
• laser doppler flowmetry
• arterial hypertension
• vascular stiffness
• vasoconstriction
• vasodilation
• antihypertensive agents
• capillaries
• arterioles