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Background: It was proposed that early vascular ageing may be an important mechanism of vascular damage in large conductance arteries. However it is not known whether aging may also affect small resistance artery morphology. Patients and methods: For this reason, we investigated 100 patients with essential hypertension. Secondary forms of hypertension were excluded according to standard clinical evaluations and biochemical or instrumental assessments. In all patients, an evaluation of small resistance arteries morphology was performed by wire micromyography. A small amount of subcutaneous tissue was obtained by local biopsy or during election surgery and subcutaneous small resistance arteries were dissected and mounted on a myograph; the media to lumen ratio (M/L) was then measured. Results: The age range of our population was 22-81 years, with a mean value of 57±12 years; 14% of them were current smokers, 32% had alterations in lipid patterns, none of them had diabetes mellitus, 58 were males and average blood pressure values were 156/95±19/12 mmHg. We found a significant correlation between M/L and age (r=0.30, p=0.002): the statistical significance of the correlation persisted after correction for confounding variables (gender, serum cholesterol, smoking status, serum glucose, systolic or diastolic blood pressure values). A statistically significant inverse correlation was also observed between internal diameter and age (r=−0.20, p=0.046). Conclusion: Our data suggest that age may affect microvascular structure in hypertensive patients. It is also possible that hypertension may anticipate the effects of physiological aging, and this should be explored in a relatively large population of normotensive subjects.

Background: It is was suggested that, in resistant hypertension, the presence of particularly pronounced microvascular alterations may contribute to explain the relative lack of response to treatment. Similarly, in diabetic patients, the persistence of an altered microvascular structure, despite the administration of multiple drug combination treatment, might partly explain the difficulty to reach target blood pressure values, especially for systolic blood pressure. Patients and methods: For this reason, we investigated a population of 94 treated essential hypertensive patients. Secondary forms of hypertension were excluded according to standard clinical evaluations and biochemical or instrumental assessment, and in all patients a 24-hour blood pressure monitoring was performed in order to exclude a white coat effect. In all patients, we evaluated small resistance arteries morphology by a wire micromyographic approach (Mulvany’s technique). A small amount of subcutaneous tissue was obtained by local biopsy or during election surgery and subcutaneous small resistance arteries were dissected and mounted on a myograph; the media to lumen ratio (M/L) was then measured. Sixteen patients had true resistant hypertension, and were compared with the remaining 78 patients with non-resistant hypertension. Results: The two groups were different in terms of mean age, pulse pressure/stroke volume, media to lumen ratio and internal diameter of small resistance arteries. Conclusion: Our data suggest that hypertensive patients with true resistant hypertension have greater microvascular structural alterations compared with non-resistant hypertensive patients. This could explain, at least in part, the resistance to pharmacological treatment and the high cardiovascular risk observed in these patients.

Macrovasculature and microvasculature are interrelated, and may influence each other. Microvascular structure is not only the site of vascular resistance but probably also the origin of most of the wave reflections generating increased central systolic blood pressure. Some index of large artery stiffness seems to be related with the media to lumen ratio of subcutaneous small resistance arteries of hypertensive patients. In addition, both microvascular structural alterations and changes in the mechanical properties of large arteries represent potent predictors of prognosis. In addition, drugs that may improve microvascular structure may also correct alterations in the mechanical properties of large arteries In fact, while β-blocking agents and diuretics have a negligible effect on microvascular structure, renin-angiotensin system antagonists and calcium entry blockers have favorable actions, improving also large artery mechanics and possibly reducing central wave reflections.