Capillary rarefaction as an index for the microvascular assessment of hypertensive patients.

Arterial hypertension represents a leading cause of cardiovascular mortality and morbidity worldwide through its detrimental effects on target organs. Therefore, the early identification and appropriate management of high-risk patients emerges as extremely important. Given that the microvasculature is subject to a series of morphological and functional changes under the continuous effect of high blood pressure, research over the last years has gradually moved toward the identification of specific microcirculatory alterations that may serve as early prognostic markers of cardiovascular risk. Dermal capillaries represent an "open window" for the in vivo study of human microcirculation that has been long used mainly for the study of rheumatic diseases. However, capillaroscopy has been relatively understudied and only recently applied in the field of hypertension. Capillaroscopy represents a forthcoming promising estimate of the microvascular status in hypertensive patients, with capillary rarefaction representing the most typical finding. The present review aims at summarizing available evidence and the main findings, as well as the premises and promises, of capillary rarefaction as a tool for evaluating patients with hypertension.