Assessment of skin microcirculation in primary aldosteronism: impaired microvascular responses compared to essential hypertensives and normotensives

Simultaneous photoplethysmography and blood flow measurements towards the estimation of blood pressure using speckle contrast optical spectroscopy

Non-invasive continuous blood pressure monitoring remains elusive. There has been extensive research using the photoplethysmographic (PPG) waveform for blood pressure estimation, but improvements in accuracy are still needed before clinical use. Here we explored the use of an emerging technique, speckle contrast optical spectroscopy (SCOS), for blood pressure estimation. SCOS provides measurements of both blood volume changes (PPG) and blood flow index (BFi) changes during the cardiac cycle, and thus provides a richer set of parameters compared to traditional PPG. SCOS measurements were taken on the finger and wrists of 13 subjects. We investigated the correlations between features extracted from both the PPG and BFi waveforms with blood pressure. Features from the BFi waveforms were more significantly correlated with blood pressure than PPG features ( R = - 0.55, p = 1.1 × 10^-4 for the top BFi feature versus R = - 0.53, p = 8.4 × 10^-4 for the top PPG feature). Importantly, we also found that features combining BFi and PPG data were highly correlated with changes in blood pressure ( R = - 0.59, p  = 1.7 × 10^-4 ). These results suggest that the incorporation of BFi measurements should be further explored as a means to improve blood pressure estimation using non-invasive optical techniques.

Blunted Microvascular Reactivity in Psoriasis Patients in the Absence of Cardiovascular Disease, as Assessed by Laser Speckle Contrast Imaging

Psoriasis is associated with accelerated rates of cardiovascular disease (CVD). Laser Speckle Contrast Imaging (LSCI) is a novel, non-interventional technique for the dynamic assessment of microvascular endothelial dysfunction, which represents an early precursor of CVD. We investigated whether skin microvascular reactivity is impaired in psoriasis and whether an association exists with large artery stiffening. Skin microvascular reactivity was assessed with LSCI combined with post-occlusive reactive hyperaemia protocol in psoriasis patients and controls in the absence of established CVD. Arterial stiffness and central hemodynamics were assessed throughout a whole 24 h period with the Mobil-O-Graph device. Most LSCI indices of microvascular reactivity were impaired in psoriasis patients (n = 90) compared to controls (n = 45) [baseline flux; occlusion flux; peak-to-baseline magnitude; baseline cutaneous vascular conductance (CVC); percentage increase in CVC, p < 0.001 for all comparisons]. In multivariate analysis, psoriatic disease predicted the above markers independently of classical CVD risk factors. Augmentation index, peripheral pulse pressure, and central systolic/diastolic blood pressure correlated with LSCI microvascular responses in the study population (n = 135). Pulse wave velocity significantly correlated with nearly all LSCI parameters, while the association with baseline flux was independent of CVD risk factors and psoriatic disease in multivariate analysis (beta = 0.096, p = 0.039). This study provides evidence of altered skin microvascular responses in psoriasis by use of LSCI, and interaction with macrovascular dysfunction, before the establishment of overt CVD. A non-interventional approach of skin microcirculation with LSCI might be used as an early indicator of vascular health in psoriasis.

Differential and targeted vesiculation: pathologic cellular responses to elevated arterial pressure

Extracellular vesicles are small membrane-enclosed particles released during cell activation or injury. They have been investigated for several decades and found to be secreted in various diseases. Their pathogenic role is further supported by the presence of several important molecules among their cargo, including proteins, lipids, and nucleic acids. Many studies have reported enhanced and targeted extracellular vesicle biogenesis in diseases that involve chronic or transient elevation of arterial pressure resulting in endothelial dysfunction, within either the general circulatory system or specific local vascular beds. In addition, several associated pathologic processes have been studied and reported. However, the role of elevated pressure as a common pathogenic trigger across vascular domains and disease chronicity has not been previously described. This review will therefore summarize our current knowledge of the differential and targeted biogenesis of extracellular vesicles in major diseases that are characterized by elevated arterial pressure leading to endothelial dysfunction and propose a unified theory of pressure-induced extracellular vesicle-mediated pathogenesis.