REAL TIME ASSESSMENT OF MICROCIRCULATION IN HYPERTENSION USING LASER SPECKLE CONTRAST ANALYSIS

Abstract

Objective: Skin microcirculation has been suggested as a model of generalized microvascular function. It has also been used as a window to access endothelial function in the microvasculature. In this study we evaluated endothelial dysfunction of skin microcirculation in hypertensive patients compared to healthy, normotensive individuals using Laser Speckle Contrast Analysis (LASCA), a novel tool to assess microcirculation non-invasively, in real time and with high reproducibility. Design and method: We studied a group of 26 untreated hypertensive patients with new-onset essential hypertension without cardiovascular comorbidities, mean age 50.5 ± 15.7 years and 13 healthy individuals matched for age, sex and body mass index. In all subjects, forearm skin blood flow was recorded under standardized conditions using a laser speckle contrast imager (PeriCam PSI NR System, Perimed, Järfälla, Sweden). Post-occlusive reactive hyperemia (PORH) was assessed following a standardized protocol and data were analyzed with signal processing software (PIMSoft, Perimed). The amplitude of PORH responses was expressed as a percentage increase between peak and baseline perfusion (%), baseline Cutaneous Vascular Conductance (CVC), peak CVC and peak CVC minus baseline CVC. The CVC was calculated as the flux divided by mean arterial pressure and expressed in perfusion units (PU)/mmHg. Results: Baseline perfusion was similar between the two groups. However, during PORH patients with hypertension showed significantly lower percentage increase from baseline to peak perfusion (145.9 ± 9.72 vs 181.68 ± 12.35 %, p = 0.019). In addition, baseline CVC (0.34 ± 0.019 vs 0.43 ± 0.03 PU/mmHg, p = 0.009) and peak CVC (0.82 ± 0.04 vs 1.2 ± 0.06 PU/mmHg, p < 0.001) were significantly lower in hypertensive patients compared to controls. Finally, PORH amplitude as expressed by peak CVC minus baseline CVC (0.48 ± 0.03 vs 0.76 ± 0.04 PU/mmHg, p < 0.001) was significantly lower in hypertensive patients compared to normotensives. Conclusions: Using LASCA, a non-contact, real-time, highly reproducible and sensitive technique for the assessment of skin microcirculation, we showed that hypertensive patients demonstrate impaired microvascular responses to stimulation tests. Endothelial dysfunction is present in the very early stages of essential hypertension, long before the establishment of overt cardiovascular disease, and LASCA may represent a novel, valuable tool for its assessment.