Evaluation of microvascular structure in humans

The evaluation of microvascular structure is, in general, not an easy task. Among the methods that may be applied to humans, plethysmographic evaluation of small arteries and wire or pressure micromyography were extensively used in the last decades. The media-to-lumen ratio of small arteries evaluated by micromyography was demonstrated to possess a strong prognostic significance; however, its extensive evaluation is limited by the local invasiveness of the assessment. Noninvasive approaches were then proposed, including capillaroscopy, which provides information about microvascular rarefaction. Recently, the interest of investigators was focused on the retinal microvascular bed. In particular, a noninvasive measurement of the wall-to-lumen ratio of retinal arterioles using scanning laser Doppler flowmetry has been introduced. Recent data suggest a rather good agreement between this approach and micromyographic measurements, generally considered the gold standard approach. Therefore, the evaluation of microvascular structure is progressively moving from bench to bedside, and it could represent, in the immediate future, an evaluation to be performed in all hypertensive patients, in order to obtain a better stratification of cardiovascular risk.