reactive hyperemia
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Examination of vascular endothelial function can help infer atherosclerosis progression. This study investigated whether vascular visualization by near-infrared (NIR) light can detect vasodilatation after cuff pressure release of the upper arm and what the correlation is between the brightness decrease ratio (R1) corresponding to vasodilation and the reactive hyperemia index (RHI). We obtained finger vascular images of 53 male subjects by photographing NIR light (wavelength 850 nm) transmitted through the middle phalanx of the middle finger with a charge-coupled device camera. The upper arm was compressed for 10 min using a cuff (200 mmHg), and vascular images before and after cuff compression release were obtained. We analyzed the finger vascular images by NIR light and digital pulse volume using endothelial peripheral arterial tonometry (Endo-PAT). We also calculated the average brightness of each vascular image. Using only the data of the ischemic finger, R1 was defined using the average brightness just before cuff release and the minimum average brightness after cuff release. The brightness of vascular images of the ischemic finger decreased after cuff release probably because of vasodilation. We found significant correlation between R1 and the RHI (r = 0.52; P < 0.001). R1 in the lowest RHI quartile was significantly smaller compared to the highest and second-highest RHI quartiles (P < 0.05). Vascular visualization by NIR light can detect vasodilation after cuff release. This is significantly correlated with the RHI on Endo-PAT.

Previous studies have linked peripheral microvascular dysfunction measured by arterial tonometry to high residual risk in on-statin patients. Digital thermal monitoring (DTM) of microvascular function is a new and simplified technique based on fingertip temperature measurements that has been correlated with the burden of atherosclerosis and its risk factors. Here, we report analyses of DTM data from two large US registries: Registry-I (6,084 cases) and Registry-II (1,021 cases) across 49 US outpatient clinics. DTM tests were performed using a VENDYS device during a 5-minute arm-cuff reactive hyperemia. Fingertip temperature falls during cuff inflation and rebounds after deflation. Adjusted maximum temperature rebound was reported as vascular reactivity index (VRI). VRI distributions were similar in both registries, with mean ± SD of 1.58 ± 0.53 in Registry-I and 1.52 ± 0.43 in Registry-II. In the combined dataset, only 18% had optimal VRI (≥2.0) and 82% were either poor (<1.0) or intermediate (1.0-2.0). Women had slightly higher VRI than men ( 1.62 ± 0.56 vs. 1.54 ± 0.47 , p < 0.001 ). VRI was inversely but mildly correlated with age ( r = − 0.19 , p < 0.001 ). Suboptimal VRI was found in 72% of patients <50 years, 82% of 50-70 years, and 86% of ≥70 years. Blood pressure was not correlated with VRI. In this largest registry of peripheral microvascular function measurements, suboptimal scores were highly frequent among on-treatment patients, possibly suggesting a significant residual risk. Prospective studies are warranted to validate microvascular dysfunction as an indicator of residual risk.

The physiological reaction of postocclusive local reactive hyperemia is regulated by neurovascular mechanisms and it reflects the function of microcirculation. Thermoregulatory changes occur first, in the form of increased skin surface temperature, which is usually followed by an increase in local blood flow. This study investigated a correlation between tourniquet duration on the upper arm, and the appearance of reactive hyperemia in the distal parts of the upper limb. Changes were registered with infrared thermometer and infrared thermography, which provided us a highly precise view of distribution of reactive hyperemia. Changes of oxygen saturation of peripheral arterial blood and blood pressure were also recorded. Our research has shown that longer duration of tourniquet leads to more intense and longer lasting reactive hyperemia in the palmar region, followed by higher temperatures of the skin surface, without any changes in postocclusive values of SpO2. Keywords: Infrared thermography, Microcirculation, Postocclusive hyperemia, Skin temperature, Tourniquet, Thermoregulatory changes.

There are concerns about altered vascular functions that could play an important role in the pathogenesis and influence the severity of chronic disease, however, increased cardiovascular risk in paediatric cystic fibrosis (CF) has not been yet fully understood. Aim was to analyse vascular disease risk and investigate changes over times in CF and controls. We prospectively enrolled 22 CF subjects (a median age of 16.07 years), and 22 healthy demographically matched controls (a median age of 17.28 years) and determined endothelial function. We utilised a combined diagnostic approach by measuring the plethysmographic Reactive Hyperemia Index (RHI) as the post-to preocclusive endothelium-dependent changes of vascular tone, and biomarkers that are known to be related to endothelial dysfunction (ED): asymmetric dimethyl arginine (ADMA), high-sensitive CRP (hsCRP), VCAM-1 and E-selectin. RHI values were significantly lower in CF young adults (p<0.005). HsCRP (p<0.005), E-selectin (p<0.001) and VCAM-1 (p<0.001) were significantly increased in CF patients since childhood. The findings have provided a detailed account of the ongoing process of microvascular dysfunction with gradual progression with the age of CF patients, making them further at risk of advanced vascular disease. Elevations of biomarkers in CF children with not yet demonstrated RHI changes but with significantly reduced RHI in adulthood and lipid profile changes indicate the possible occurrence of ED with CF-related specific risk factors over time and will enable us to provide the best possible support.

Aims: In this pre-specified analysis of the “endothelium, stent and antiplatelet therapy” study, we investigate the impact of antiplatelet therapies on microvascular function in patients undergoing stenting for an acute coronary syndrome.Methods and Results: Fifty-six patients [age: 63(55–67) years, males, 10 diabetics, 27 non-ST-elevation myocardial infarction] were randomized to receive clopidogrel, ticagrelor or prasugrel in form of oral loading 2 h before stenting followed by oral therapy. Investigators were blinded to the allocation. Laser-Doppler microvascular function and ADP-induced platelet aggregation capacity were measured at baseline, 2 h after oral antiplatelet loading, and 1 day, 1 week and 1 month after stenting during chronic therapy with the same antiplatelet agent. Platelet aggregation decreased in all groups 2 h after oral loading, with a significantly larger effect in the prasugrel group (P = 0.009). Similarly, prasugrel and ticagrelor loading was followed by an increase in microvascular reactive hyperemia (P = 0.007 and P = 0.042 compared to clopidogrel). This effect disappeared one day after coronary intervention, with a significant decrease in the prasugrel group (P = 0.026). Similarly, analysis of microvascular conductance showed a larger increase in the prasugrel group 2 h after loading (P = 0.022 among groups), and a decrease in all groups after stenting.Conclusions: Oral loading with prasugrel (and less consistently ticagrelor) is associated with improved microvascular function and stronger platelet inhibition in acute coronary syndrome patients. The microvascular effect was however lost 1 day after stenting and during subsequent follow-up. Further studies are necessary to clarify the the long-term effects and potential benefits of P2Y12 inhibitors on microvascular damage.ClINICALTRIALS.gov N°: NCT01700322EUDRACT-N°: 2011-005305-73.

Background: Childhood cancer survivors (CCS) are at an increased risk for cardiovascular diseases (CVD). It was the primary aim of this study to determine different measures of cardiac, carotid, lipid, and apolipoprotein status in young adult CCS and in healthy controls.Methods: Cardiac and common carotid artery (CCA) structure and function were measured by ultrasonography. Lipids and apolipoproteins were measured in the blood. Peripheral arterial endothelial vasomotor function was assessed by measuring digital reactive hyperemia index (PAT-RHI) using the Endo-PAT 2000.Results: Fifty-three CCS (20–30 years, 35 men) and 53 sex-matched controls were studied. The CCS cohort was divided by the median dose of anthracyclines into a low anthracycline dose (LAD) group (50–197 mg/m2, n = 26) and a high anthracycline dose (HAD) group (200–486 mg/m2, n = 27). Carotid distensibility index (DI) and endothelial function determined by PAT-RHI were both lower in the CCS groups compared with controls (p &lt; 0.05 and p = 0.02). There was no difference in carotid intima media thickness. Atherogenic apolipoprotein-B (Apo-B) and the ratio between Apo-B and Apoliprotein-A1 (Apo-A1) were higher in the HAD group compared with controls (p &lt; 0.01). Apo-B/Apo-A1-ratio was over reference limit in 29.6% of the HAD group, in 15.4% of LAD group, and in 7.5% of controls (p = 0.03). Measured lipid markers (low density lipoprotein and total cholesterol and triglycerides) were higher in both CCS groups compared with controls (p &lt; 0.05). Systolic and diastolic function were measurably decreased in the HAD group, as evidenced by lower EF (p &lt; 0.001) and lower é-wave (p &lt; 0.005) compared with controls. CCA DI correlated with Apo-B/Apo-A1-ratio and Apo-A1. Follow-up time after treatment correlated with decreased left ventricular ejection fraction (p = 0.001).Conclusion: Young asymptomatic CCS exhibit cardiac, vascular, lipid, and apolipoprotein changes that could account for increased risk for CVD later in life. These findings emphasize the importance of cardiometabolic monitoring even in young CCS.

Abstract This prospective study determined the effects of hypoglycemic stimulation on vascular endothelial function in non-diabetic patients using reactive hyperemia peripheral arterial tonometry (RH-PAT). The study included non-diabetic patients who were hospitalized for an insulin tolerance test (ITT) for the diagnosis of hypoadrenocorticism or hypopituitarism. Vascular endothelial function was assessed using the reactive hyperemia index (RHI) measured by the RH-PAT. We also measured the levels of anterior pituitary hormone, adrenaline, noradrenaline, and dopamine at the time of hypoglycemia. The primary endpoint was a change in the RHI at 120 minutes after insulin administration. The study included 27 patients. ITT was associated with significant increases in systolic blood pressure, pulse rate, and the blood levels of adrenocorticotropic hormone, cortisol, growth hormone, adrenaline, noradrenaline, and dopamine. RHI significantly decreased after ITT from 2.24±0.51 to 1.71±0.42. A significant inverse correlation was observed between the change in RHI and change in adrenaline (r=-0.670, p=0.012). We concluded that hypoglycemic stimulation altered vascular endothelial function, as measured by RH-PAT, even in patients free of glucose intolerance. The observed deterioration in vascular endothelial function correlated with increases in catecholamine levels during hypoglycemia.Trial registration: UMIN000033244

Exposure to uninterrupted prolonged sitting leads to macro- and microvascular complications, which can contribute to increased cardiovascular disease risk. This study investigated the macrovascular and microvascular responses to 3 h of sitting that was: (i) uninterrupted (CON); and (ii) interrupted every 20 min with 1 min light intensity half squats plus calf raises (EX). Twenty healthy participants (21 [SD: 2] years; 21.5 [SD: 1.6] kg/m2) were recruited to participate in this randomized cross-over trial. Macrovascular function was quantified using brachial–ankle pulse wave velocity (baPWV) and the lower- and upper-limb arterial stiffness index (ASI). Microvascular function was quantified as the medial gastrocnemius tissue oxygen saturation (StO2) area under the curve (AUC) during reactive hyperemia. The baPWV did not significantly change with time ( p = 0.594) or by condition ( p = 0.772). The arm ASI increased by 3.6 (95% CI: 0.7 to 6.6, effect size [ES] = 0.27) with a nonsignificant condition effect ( p = 0.219). There was a significant interaction effect for leg ASI ( p = < 0.001), with ASI increasing (impairment) by 18.7 (95% CI: 12.1 to 25.3, ES = 0.63) for CON and decreasing (improvement) by −11.9 (95% CI: −18.5 to −5.3, ES = 0.40) for EX compared to presitting. Similarly, the AUC decreased (detrimental) by 18% (Δ = −321, 95% CI: −543 to −100, ES = 0.32) for CON and increased by 32% (Δ = 588, 95% CI: 366 to 809, ES = 0.59) for EX. The leg ASI was inversely associated with StO2 AUC (interclass correlation coefficient: −0.66, 95% CI: −0.51 to −0.77). These preliminary findings suggest that regularly interrupting prolonged sitting with simple bodyweight exercises may help to preserve lower-limb vascular function.