Sensibility and specificity of laser speckle contrast imaging according to Endo-PAT index in type 1 diabetes

Vascular Aging and Damage in Patients with Iron Metabolism Disorders

Vascular aging is a physiological, multifactorial process that involves every type of vessel, from large arteries to microcirculation. This manifests itself as impaired vasomotor function, altered secretory phenotype, deteriorated intercellular transport function, structural remodeling, and aggravated barrier function between the blood and the vascular smooth muscle layer. Iron disorders, particularly iron overload, may lead to oxidative stress and, among other effects, vascular aging. The elevated transferrin saturation and serum iron levels observed in iron overload lead to the formation of a non-transferrin-bound iron (NTBI) fraction with high pro-oxidant activity. NTBI can induce the production of reactive oxygen species (ROS), which induce lipid peroxidation and mediate iron-related damage as the elements of oxidative stress in many tissues, including heart and vessels' mitochondria. However, the available data make it difficult to precisely determine the impact of iron metabolism disorders on vascular aging; therefore, the relationship requires further investigation. Our study aims to present the current state of knowledge on vascular aging in patients with deteriorated iron metabolism.

Biochemical and clinical markers of endothelial dysfunction do not outweigh traditional risk factors for the presence of diabetic retinopathy in patients with type 1 diabetes

BACKGROUND

This study aimed to evaluate whether soluble vascular cytoadhesive molecule-1 (sVCAM-1), intracellular cytoadhesive molecule-1 (sICAM-1), and endothelial function as assessed by EndoPat outweighed traditional risk factors for the presence of diabetic retinopathy (DR) in patients with type 1 diabetes (T1D).

METHODS

Patients aged ≥ 12 years completed a clinical-epidemiological questionnaire. Fasting venous blood samples were obtained (lipid profile, glycemic control, and C-reactive protein levels). Vascular reactivity was assessed via peripheral arterial tonometry performed by supplying the reactive hyperemia index (RHI) through the EndoPAT device. sVCAM-1 and sICAM-1 levels were measured using multiplex assays.

RESULTS

Data were obtained from 187 patients (51.3% female), aged 32 ± 13 years with a disease duration of 14 (6-15) years and mean hemoglobin A1c (HbA1c) of 9.1% ± 2.1%. After adjustments were made, age, HbA1c, arterial blood pressure, and use of drugs that could interfere with endothelial function were found to be associated with DR. No association was noted with sVCAM-1 and sICAM-1 levels and RHI.

CONCLUSIONS

In our sample, sVCAM-1, sICAM and EndoPAT did not outweigh the traditional DR risk factors, such as age, high HbA1c, arterial blood pressure, and use of drugs that could interfere with endothelial function and are significantly associated with DR. Further prospective studies should evaluate if markers of endothelial dysfunction could predict diabetes-related micro and macrovascular complications in T1D.

Detection of cutaneous oxygen saturation using a novel snapshot hyperspectral camera: a feasibility study

Background

Tissue necrosis, a consequence of inadequate tissue oxygenation, is a common post-operative complication. As current surgical assessments are often limited to visual and tactile feedback, additional techniques that can aid in the interrogation of tissue viability are needed to improve patient outcomes. In this bi-institutional pilot study, the performance of a novel snapshot hyperspectral imaging camera to detect superficial cutaneous oxygen saturation (StO₂) was evaluated.

Methods

Healthy human volunteers were recruited at two participating centers. Cutaneous StO₂ of the forearm was determined by a snapshot hyperspectral camera on two separate study days during occlusion-reperfusion of the brachial artery and after induction of local vasodilation. To calculate the blood StO₂ at each pixel in the multispectral image, spectra were selected, and fitting was performed over wavelengths ranging from 470 to 950 nm.

Results

Quantitative detection of physiological changes in cutaneous StO₂ levels was feasible in all sixteen volunteers. A significant (P<0.001) decrease in cutaneous StO₂ levels from 78.3% (SD: 15.3) at baseline to 60.6% (SD: 19.8) at the end of occlusion phase was observed, although StO₂ levels returned to baseline after five minutes. Mean cutaneous StO₂ values were similar in the same subjects on separate study days (Pearson R2: 0.92 and 0.77, respectively) at both centers. Local vasodilation did not yield significant changes in cutaneous StO₂ values.

Conclusions

This pilot study demonstrated the feasibility of a snapshot hyperspectral camera for detecting quantitative physiological changes in cutaneous StO₂ in normal human volunteers, and serves as a precursor for further validation in perioperative studies.

Obesity-Related Inflammation and Endothelial Dysfunction in COVID-19: Impact on Disease Severity

The coronavirus disease 2019 (COVID-19) pandemic has put into evidence another pandemic – obesity. Currently, several studies have documented the association between obesity and COVID-19 severity. The mechanisms underlying the increased risk of complications and mortality in obese patients with COVID-19 are of diverse nature. Inflammation plays a central role in obesity. Metabolic alterations seen in obese patients are related to an inflammatory response, and several studies report elevated levels of circulating inflammatory cytokines in obese patients. Also, deregulated expression of adipokines, such as leptin and resistin, increase the expression of vascular adhesion molecule 1 and intercellular adhesion molecule 1 that contribute to increased vascular leukocyte adhesiveness and additional oxidative stress. Additionally, it is now recognized that the chronic impairment of systemic vascular endothelial function in patients with cardiovascular and metabolic disorders, including obesity, when intensified by the detrimental effects of SARS-CoV-2 over the endothelium, may explain their worse outcomes in COVID-19. In fact, vascular endothelial dysfunction may contribute to a unfavorable response of the endothelium to the infection by SARS-CoV-2, whereas alterations in cardiac structure and function and the prothrombotic environment in obesity may also provide a link to the increased cardiovascular events in these patients.

Effects of Low-Level Tragus Stimulation on Endothelial Function in Heart Failure With Reduced Ejection Fraction

BACKGROUND

Autonomic dysregulation in heart failure with reduced ejection fraction plays a major role in endothelial dysfunction. Low-level tragus stimulation (LLTS) is a novel, noninvasive method of autonomic modulation.

METHODS AND RESULTS

We enrolled 50 patients with heart failure with reduced ejection fraction (left ventricular ejection fraction of ≤40%) in a randomized, double-blinded, crossover study. On day 1, patients underwent 60 minutes of LLTS with a transcutaneous stimulator (20 Hz, 200 μs pulse width) or sham (ear lobule) stimulation. Macrovascular function was assessed using flow-mediated dilatation in the brachial artery and cutaneous microcirculation with laser speckle contrast imaging in the hand and nail bed. On day 2, patients were crossed over to the other study arm and underwent sham or LLTS; vascular tests were repeated before and after stimulation. Compared with the sham, LLTS improved flow-mediated dilatation by increasing the percent change in the brachial artery diameter (from 5.0 to 7.5, LLTS on day 1, P = .02; and from 4.9 to 7.1, LLTS on day 2, P = .003), compared with no significant change in the sham group (from 4.6 to 4.7, P = .84 on day 1; and from 5.6 to 5.9 on day 2, P = .65). Cutaneous microcirculation in the hand showed no improvement and perfusion of the nail bed showed a trend toward improvement.

CONCLUSIONS

Our study demonstrated the beneficial effects of acute neuromodulation on macrovascular function. Larger studies to validate these findings and understand mechanistic links are warranted.

Painless local pressure application to test microvascular reactivity to ischemia

BACKGROUND

Forearm cutaneous blood flux (CBF) measurement with post-occlusive reactive hyperemia (PORH) is uncomfortable and may not be devoid of risks. We aimed to investigate post-compression reactive hyperemia (PCRH) with a custom-made indenter that was designed to be easily used routinely by inexperienced observers.

METHODS

Medical students evaluated PCRH with 1- to 4-min pressure applications of 16 to 34 kPa and PORH with 3-min forearm cuff occlusion using laser speckle contrast imaging in 15 healthy volunteers. Participants were asked to quantify their discomfort with a visual analogue scale (VAS) of 10 cm. Total ischemia (ISCH) was quantified by the product of CBF during ischemia and ischemia duration (min). We subtracted the CBF changes in the skin from a reference ipsilateral (PCRH) or contralateral (PORH) non-stimulated area.

RESULTS

The average VAS was 1.0 for PCRH vs. 6.0 for PORH (p < 0.001). A strong linear relationship between ISCH and peak PCRH (r² = 0.915, p < 0.001) was noted. Peak PORH values (63.9 laser perfusion units (LPU)) were significantly lower than all values of the 3-min PCRH (72.6 LPU), including the one obtained with 16 kPa.

CONCLUSION

Inexperienced observers could test microvascular reactivity with PCRH without inducing the discomfort that is typically experienced with PORH. Further, PCRH elicits a higher peak response to ischemia compared with PORH. This extremely simple method could influence a broad spectrum of routine cutaneous microcirculation investigations, especially when a painful approach is particularly inadequate or if the patient is fragile.

CLINICAL TRIAL REGISTRATION

NCT02861924.