Postocclusive Reactive Hyperemia Research Articles

Objective assessment of skin microcirculation using a smartphone camera.

Existing techniques for assessment of microcirculation are limited by their large size and high costs and are often not so easy to use. Advances in mobile technology have enabled great improvements in smartphone sensor technology. In this study, we used SkinSight, an app for iPhone and iPad, to measure changes in skin microcirculation during physiological provocations. The system estimates changes in the concentration of hemoglobin in the skin by analyzing the reflected light emitted from the built-in light-emitting diode and detected by the camera of the smartphone. A relative hemoglobin (Hb) index was measured during a 5-min arterial occlusion, post-occlusive reactive hyperemia, and a 5-min venous occlusion in 10 healthy subjects, on two separate days. The index was calculated in an area of the skin from the color information in the images acquired by the phone camera. Polarized light spectroscopy imaging was used to measure changes in red blood cell concentration for comparison. During arterial occlusion, relative Hb index was unchanged compared to baseline (P = .40). After release of the cuff, a sudden 60%-75% increase in Hb index was observed (P < .001) followed by a gradual return to baseline. During venous occlusion, Hb index increased by 80% (P < .001) followed by a gradual decrease to baseline after reperfusion. Day-to-day reproducibility of the relative Hb index was excellent (ICC: 0.92, r = 0.94), although relative Hb index was consistently higher during the second day, possibly as a result of changed lighting conditions or calibration issues. Microvascular responses to physiological provocations in the skin can be accurately and reproducibly measured using a smartphone application. Although the system offers a handheld, easy to use and flexible technique for skin microvascular assessment, the effects of lighting on the measured values and need for calibration need to be further investigated.

Comparison Of Whole-forearm And Skin Post-occlusive Reactive Hyperemia As Indices Of Microvascular Function

BACKGROUND: Post-occlusive reactive hyperemia (PORH) is often used as a test of microvascular function. However, the method of PORH measurement and the reporting of PORH values varies widely between studies, from measurements on the skin or whole-forearm to reporting peak or cumulative PORH values. As such, the optimal measurement and reporting of PORH values remains unclear. PURPOSE: To compare whole-forearm and skin PORH between older adults with conditions typically associated with microvascular dysfunction (type 2 diabetes, T2D), macrovascular dysfunction (non-diabetic coronary artery disease, CAD) and healthy controls (CTRL). METHODS: We retrospectively analyzed data obtained from 13 T2D patients (61 ± 9 years, 6 M ; 7 W), 21 CAD patients (65 ± 9 years, 18 M ; 3 W) and 13 CTRL (65 ± 7 years, 9 M ; 4 W). Forearm vascular conductance (FVC, duplex ultrasound) and cutaneous vascular conductance (CVC, laser-Doppler) were measured simultaneously before and for 3 minutes after 5 minutes of forearm ischemia. PORH was quantified as: absolute peak (Peak), change from baseline to peak (∆) and area under the curve above baseline (AUC). RESULTS: Baseline FVC (P=0.84) and CVC (P=0.31) were similar between groups. Peak FVC was similar between groups (P=0.24), while ∆FVC tended to be reduced in T2D compared to CAD (P=0.06) and CTRL (P=0.07). FVC AUC was reduced in T2D compared to CTRL (P=0.03), while values in CAD did not differ from T2D or CTRL. Peak CVC (T2D: P=0.04, CAD: P=0.02) and ∆CVC (T2D: P=0.03, CAD: P=0.01) were reduced in T2D and CAD. There was a trend for CVC AUC to differ between groups (P=0.06). The different indices of PORH for a given measurement (forearm vs skin) were strongly correlated (r=0.755 to 0.906 between FVC descriptors, r=0.768 to 0.991 between CVC descriptors, all P<0.001). However, FVC indices of PORH weakly correlated with CVC indices (r=0.237 to 0.374, P=0.01 to 0.11). CONCLUSIONS: Whole-forearm and skin PORH provide different information on microvascular function in older adults. A decreased PORH in the whole-forearm appears to be a feature of T2D and not CAD, while a decreased PORH in forearm skin seems to be detectable in both T2D and CAD.

Acute Vascular Benefits of Finnish Sauna Bathing in Patients With Stable Coronary Artery Disease

BackgroundFinnish sauna bathing habits are associated with a decreased risk of cardiovascular mortality. The physiologic adaptations mediating this association remain to be fully elucidated. This study tested the hypothesis that Finnish sauna bathing acutely improves peripheral flow-mediated dilation (FMD) in middle-aged and older adults with stable coronary artery disease (CAD). MethodsTwenty-two adults (20 male, 2 female; 67 ± 10 years) with stable CAD underwent 2 periods of 10 minutes in a Finnish sauna (81.3 ± 2.7°C, 23 ± 3% humidity) separated by 10 minutes of thermoneutral rest. Before and 51 ± 8 minutes after sauna bathing, brachial artery FMD and postocclusive reactive hyperemia (PORH) were evaluated by means of Doppler ultrasound. ResultsSauna bathing increased core temperature (mean +0.66°C [95% CI 0.54-0.77], P < 0.01) and heart rate (+27 beats/min [24-29], P < 0.01), and decreased systolic (−19 mm Hg [−31 to −6]; P < 0.01) and diastolic (−6 mm Hg [−11 to −1], P < 0.01) blood pressures. Brachial artery FMD was greater after sauna bathing (+1.21% [0.16-2.26], P = 0.04), whereas PORH was unchanged (peak: +0.51 mL/min/mm Hg [−0.13 to 1.15], P = 0.11; area under the curve: +0.21 mL/mm Hg [−0.12 to 0.54]; P = 0.19). ConclusionsA typical Finnish sauna bathing session acutely improves peripheral FMD in middle-aged and older adults with stable CAD.

Flowmotion Monitored by Flow Mediated Skin Fluorescence (FMSF): A Tool for Characterization of Microcirculatory Status.

Oscillations in the microcirculation, known as flowmotion, are a well-recognized characteristic of cutaneous blood flow. Since flowmotion reflects the microcirculatory status of the vascular system, which is very often impaired in many diseases and disorders, a quantitative assessment of skin flowmotion could potentially be used to screen for early symptoms of such conditions. In this study, skin flowmotion was monitored using the Flow Mediated Skin Fluorescence (FMSF) technique. The flowmotion parameter was used for quantitative assessment of basal flowmotion both at rest (FM) and during reperfusion [FM(R)] following the post-occlusive reactive hyperemia (PORH). The study population was composed of healthy volunteers between the ages of 30 and 72 (n = 75). The FM parameter showed an inverse dependence relative to age, while the FM(R) parameter was inversely correlated to blood pressure. The FM(R) parameter reflects the strong effect of hypoxia on flowmotion, which is mainly due to increased myogenic activity in the vessels. The FMSF technique appears to be uniquely suited for the analysis of basal flowmotion and the hypoxia response, and may be used for the characterization of microcirculatory status.

Dysregulated Neurovascular Control Underlies Declining Microvascular Functionality in People With Non-alcoholic Fatty Liver Disease (NAFLD) at Risk of Liver Fibrosis.

Background/AimsIncreasing evidence shows that non-alcoholic fatty liver disease (NAFLD) is associated with dysregulation of microvascular perfusion independently of established cardio-metabolic risk factors. We investigated whether hepatic manifestations of NAFLD such as liver fibrosis and liver fat are associated with microvascular hemodynamics through dysregulation of neurovascular control.MethodsMicrovascular dilator (post-occlusive reactive hyperemia) and sympathetically mediated constrictor (deep inspiratory breath-hold) responses were measured at the forearm and finger, respectively, using laser Doppler fluximetry. Non-linear complexity-based analysis was used to assess the information content and variability of the resting blood flux (BF) signals, attributable to oscillatory flow-motion activity, and over multiple sampling frequencies.ResultsMeasurements were made in 189 adults (113 men) with NAFLD, with (n = 65) and without (n = 124) type 2 diabetes mellitus (T2DM), age = 50.9 ± 11.7 years (mean ± SD). Microvascular dilator and constrictor capacity were both negatively associated with age (r = −0.178, p = 0.014, and r = −0.201, p = 0.007, respectively) and enhanced liver fibrosis (ELF) score (r = −0.155, p = 0.038 and r = −0.418, p < 0.0001, respectively). There was no association with measures of liver fat, obesity or T2DM. Lempel-Ziv complexity (LZC) and sample entropy (SE) of the BF signal measured at the two skin sites were associated negatively with age (p < 0.01 and p < 0.001) and positively with ELF score (p < 0.05 and p < 0.0001). In individuals with an ELF score ≥7.8 the influence of both neurogenic and respiratory flow-motion activity on LZC was up-rated (p < 0.0001).ConclusionAltered microvascular network functionality occurs in adults with NAFLD suggesting a mechanistic role for dysregulated neurovascular control in individuals at risk of severe liver fibrosis.

P0162HEMODIALYSIS AND PERITONEAL DIALYSIS PATIENTS HAVE SEVERELY IMPAIRED ENDOTHELIAL POST-OCCLUSIVE FOREARM VASODILATORY RESPONSE ASSESSED WITH LASER SPECKLE CONTRAST IMAGING

Abstract Background and Aims Endothelial dysfunction is associated with cardiovascular events and mortality in various disease states, including end-stage-renal-disease (ESRD). Novel technological approaches have emerged for real-time assessment of endothelial reactivity. This study examined forearm skin microcirculation using Laser Speckle Contrast Imaging (LSCi) before and after arterial occlusion in ESRD patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) Method 38 patients undergoing HD were matched in a 1:1 ratio with 38 PD patients (for age, sex and dialysis vintage) and 38 controls (for age and sex). Skin microvascular reactivity parameters assessed with LSCI included baseline perfusion, occlusion perfusion, and peak perfusion during post-occlusive reactive hyperemia (PORH); time to peak perfusion; proportional change from baseline to peak perfusion; baseline and peak cutaneous vascular conductance (CVC); proportional change from baseline to peak CVC; and the amplitude of the PORH response (calculated as the difference between peak and baseline CVC). Results Baseline perfusion [HD: 46.97±14.6; PD: 49.32±18.07; controls: 42.02±11.94 Laser-Specle-Perfusion-Units (LSPU), p=0.097] and peak post-occlusion perfusion (104.77±28.68 vs 109.04±40.77 vs 116.96±30.96 LSPU, p=0.238) did not differ between groups. However, the post-occlusive vascular response was completely different, since time to peak response (HD: 7.24±6.99; PD: 10.68±9.45; controls: 11.11±5.1 sec, p=0.003) and the (%) increase from baseline to peak perfusion (HD: 133%±66; PD: 149%±125; controls: 187%±61, p=0.001) was significantly lower in ESRD patients. ESRD patients had also lower levels of peak CVC, indicating the maximum capillary recruitment (HD: 1.05±0.3; PD: 1.07±0.44; controls: 1.57±0.52 LSPU/mmHg, p&amp;lt;0.001), lower % increase of CVC at peak (p=0.001), and lower amplitude of the PORH response (p=0.001) (a measure of the difference between baseline and maximum capillary recruitment). Conclusion Using this novel non-invasive technology endothelial post-occlusive skin vasodilatory response was found to be similar between HD and PD patients and significantly impaired compared to controls. Future studies are needed to assess the prognostic implications of this microcirculatory functional defect.

P1012NAIL CAPILLARY DENSITY DURING POSTOCCLUSIVE REACTIVE HYPEREMIA AND VENOUS CONGESTION IS MORE IMPAIRED IN DIABETIC COMPARED TO NON-DIABETIC CKD PATIENTS

Abstract Background and Aims Αlterations in endothelial function and capillary circulation have been associated with increased cardiovascular events and overall mortality. Both diabetes mellitus (DM) and chronic kidney disease (CKD) have been associated with microcirculatory damage. Nailfold video-capillaroscory can provide a thorough assessment of capillary density and microcirculation changes. This is the first study examining in comparison microcirculatory function parameters in diabetic and non-diabetic patients with CKD. Method We included 48 diabetic and 48 non-diabetic adult patients (&amp;gt;18 years) with CKD (eGFR: &amp;lt;90 and ≥15mL/min/1.73m2), matched in a 1:1 ratio for age, sex and eGFR within each CKD stage (2, 3a, 3b and 4). All participants underwent nailfold video-capillaroscopy, during which capillary density was measured at normal conditions (baseline), after a 4-minute arterial occlusion (postocclusive reactive hyperemia) and at the end of a 2-minute venous occlusion (congestion phase). Results Baseline demographic, anthropometric and laboratory characteristics were similar between patients with and without diabetes in total and in CKD stages. Overall, no significant differences at baseline capillary density were observed between groups; however diabetic patients presented significantly lower capillary density during reactive hyperemia (36.3±3.8 vs 38.3±4.3 capillaries/mm2, p=0.022) and at venous congestion (37.8±4.0 vs 39.8±4.2 capillaries/mm2, p=0.015). When stratified according to CKD stages, the between-group differences in parameters of interest were not significant in stages 2, 3a and 4. In stage 3b, capillary density was significantly lower in diabetic compared to non-diabetic subjects at baseline (31.1±2.8 vs 33.4±3.4 capillaries/mm2, p=0.044), during postocclusive hyperemia (36.8±2.7 vs 40.0±4.3 capillaries/mm2, p=0.037) and venous congestion (38.3±2.8 vs 41.5±3.5 capillaries/mm2, p=0.022). Conclusion Capillary density during postocclusive reactive hyperemia and after venous congestion is lower in diabetic compared to non-diabetic CKD patients, a finding indicative that diabetes is an additional factor contributing to microcirculatory functional impairment in CKD. These differences are more prominent in CKD stage 3b, and less prominent in earlier and later stages.

1518-P: Worsening of Microvascular Reactivity and Markers of Endothelial Activation and Oxidative Stress in Patients with Stabilized Type 1 Diabetes: 3-Year Follow-Up

Endothelial activation accelerated by oxidative stress (OxS) is believed to be the major step in development of diabetes angiopathy. The aim of this follow-up study was to measure microvascular reactivity (MVR) and markers of OxS. Our study involved 87 patients with type 1 diabetes (aged 37 ± 15 yrs, HbA1C 7.8 ± 1.5 % DCCT, DM duration 18 ± 11 yrs). MVR was evaluated from post-occlusive reactive hyperemia (PORH) by Laser-Doppler fluxmetry (Perimed) and skin autofluorescence (SAF), reflecting advanced glycation endproducts (AGEs) accumulation, was assessed by AGE-Reader (Diagnoptics). OxS was evaluated by malondialdehyde (MDA), derivatives of reactive oxygen metabolites (d-ROMs) test and plasma antioxidant test (PAT) (FRAS4). Markers of endothelial activation (ICAM-1, VCAM-1, vWF) and routine biochemical and biometrical parameters were evaluated in all patients during 3 years of follow-up. Diabetes control slightly improved during the study period (HbA1c 7.8 ± 1.5 vs. 7.5 ± 1.4 % DCCT, p&amp;lt;0.05), while SAF remained almost unchanged (2.1 ± 0.5 vs. 2.3 ± 0.5 AU, ns). Worsening of MVR was observed (Time to max PORH 12.7 vs. 17.5 s, p&amp;lt;0.05). Significant increase in VCAM-1 was present (718 ± 186 vs. 918 ± 550 pg/L, p&amp;lt;0.005), while ICAM-1 and vWF did not change significantly. Both higher MDA (0.70 ± 0.26 vs. 0.81 ± 0.23 µmol/L, p&amp;lt;0.05) and PAT (2431 ± 645 vs. 2944 ± 466 U Cor, p&amp;lt;0.0001) were observed. Skin autofluorescence was positively associated with vibration perception threshold (r=0.45, p&amp;lt;0.0001) and HbA1c (r=0.24, p&amp;lt;0.005). Although diabetes control slightly improved, we observed further progression of endothelial dysfunction and oxidative stress in our T1D patients. Higher AGEs accumulation in patients with worse glucose control was associated with impaired vibration perception threshold. It is questionable whether boosted human antioxidant capacity in subject with increased OxS could be considered protective and beneficial. Disclosure J. Skrha: Advisory Panel; Self; Boehringer Ingelheim International GmbH. Speaker’s Bureau; Self; Eli Lilly and Company, Merck Sharp &amp; Dohme Corp. J. Soupal: Advisory Panel; Self; Abbott. Consultant; Self; Medtronic, Roche Diabetes Care. Speaker’s Bureau; Self; Dexcom, Inc. M. Prazny: Speaker’s Bureau; Self; Novartis Pharmaceuticals Corporation, Roche Diabetes Care. Other Relationship; Self; Abbott, Boehringer Ingelheim International GmbH, Lilly Diabetes, Medtronic, Novo Nordisk A/S, Sanofi, Teva Pharmaceutical Industries Ltd. Funding RVO VFN64165, Progres Q25

P1161CUTANEOUS MICROCIRCULATORY DYSFUNCTION IN PERITONEAL DIALYSIS PATIENTS

Abstract Background and Aims Microvascular impairment is an early step in cardiovascular disease (CVD), the major cause of morbidity and mortality in patients with CKD. Changes in skin microvascular reactivity have been shown to reflect more widespread changes in the systemic and coronary microcirculation. Microvascular function is attenuated by advancing age and conditions that commonly coexist with CKD such as diabetes and hypertension. We investigated whether skin microvascular reactivity is impaired in peritoneal dialysis (PD) patients compared with healthy controls and whether this impairment is independent of comorbidity. Method Forearm skin vasculature was examined in 27 healthy controls, 27 patients on PD and 27 controls matched to the PD patients for age, gender, diabetes and previous CV events. Microvascular function was assessed using laser Doppler flowmetry in combination with post-occlusive reactive hyperaemia (a test of generalised microvascular function) and iontophoretic application of acetylcholine (ACh) and sodium nitroprusside (SNP) to investigate endothelium dependant and non-endothelium dependant vasodilation respectively. Results Peak post-occlusive flow was lower in the PD patients than in both the healthy controls and the co-morbidity matched group; 90.45 AU (60.9-128.35) in healthy controls, 73AU (58.8-134.4) in matched controls and 56.95AU (45.1-89.8) in PD patients (p=0.0239 healthy controls versus patients, p=0.0373 matched controls versus patients). SNP-mediated vasodilatation was statistically lower in the PD group compared with healthy controls (p= 0.016), ACh response was lower but did not reach statistical significance (p= 0.076). ACh and SNP-mediated vasodilatation trended towards being lower in PD patients than matched controls but did not reach statistical significance. Conclusion The PD patients were characterised by a generalised dysfunction of the skin microcirculation compared with healthy controls and controls matched for factors known to affect the microcirculation. This appears to be the result of impaired endothelium dependant and independent vasodilatory mechanisms.

Micro- and macrovascular function in patients suffering from primary adrenal insufficiency: a cross-sectional case\u2013control study

BackgroundDespite adequate glucocorticoid (GC) and mineralocorticoid (MC) replacement therapy, patients suffering from primary adrenal insufficiency (AI) have an increased mortality, mainly due to cardiovascular diseases. Only little knowledge exists on the contribution of MC substitution to the cardiovascular risk. Therefore, this study investigates the impact of plasma renin concentration on parameters of micro- and macrovascular function.Methods26 patients with primary AI [female = 18, age: 51 (28; 78) years; BMI: 24 (18; 40) kg/m2; disease duration: 18 (5; 36) years] were included in this cross-sectional analysis. Intima media thickness (IMT) and pulse wave velocity (PWV) were investigated to assess macrovascular remodeling and arterial stiffness. Microvascular function was estimated by post-occlusive reactive hyperemia using laser Doppler fluxmetry. Baseline perfusion, biological zero, peak perfusion, time to peak and recovery time were recorded. Patients were grouped according to their median plasma renin concentration of previous visits (Reninhigh vs Reninlow) and were compared to a group of healthy women [age: 44 (43; 46) years; BMI: 24.2 (21.8; 27.5)].ResultsPWV was significantly higher in AI patients compared to controls [9.9 (5; 18.5) vs 7.3 (6.8; 7.7) m/s; p < .01], whereas no differences in microvascular function could be found. In Reninlow time to peak perfusion was significantly longer [6.0 (3; 15) vs 3.5 (1.5; 11) s; p < .05], whereas no differences in IMT and PWV were observed between Reninhigh and Reninlow. No impact of GC dose was observed.ConclusionsMicrovascular function is not impaired in patients with primary AI under adequate replacement therapy, although higher renin concentrations are associated with subclinical improvements. No relation between RAAS activity and macrovascular function is observed, while arterial stiffness might be increased in primary AI.

Postocclusive reactive hyperemia and thermal response in the skin microcirculation of subjects with spinal cord injury

The response of skin blood cell flux (SBF) to locally applied pressure was evaluated by laser Doppler fluxmetry over the sacrum and the gluteus maximus muscle in twenty patients with spinal cord injuries (SCI)-ten with tetraplegia, ten with paraplegia-and ten healthy subjects. The SCI patients were further divided into two subgroups, one with sensation and the other without sensation over the sacrum area. The SBF over the sacrum, without applied pressure, showed somewhat higher values among the patients. The ten paraplegic patients (p less than 0.05) and the subgroup of patients without sensation over the sacrum (p less than 0.05) showed the highest values. Occlusion of the SBF was reached at a lower external skin pressure over the sacrum than over the gluteus maximus muscle in the group with spinal cord injuries (p less than 0.01). During the postocclusive reactive hyperemia we found a much shorter time to peak SBF over the gluteus muscle for the patients compared to the healthy subjects (p less than 0.01). In the subgroup of patients without sensation over the sacrum a prolonged time to peak SBF was found (p less than 0.01) over the sacrum compared to patients with sensation and to healthy subjects. The increase of the SBF during postocclusive hyperemia response was lower over both the sacrum and the gluteus maximus muscle areas in the patients with spinal cord injuries (p less than 0.01).

Sirt1 during childhood is associated with microvascular function later in life.

Microvascular dysfunction often precedes other age-related macrovascular conditions and predicts future cardiovascular risk. Sirtuin 1 (Sirt1) has recently emerged as a protein that protects the vasculature and reduces the risk of cardiovascular diseases. We tested the hypothesis that lower Sirt1 during childhood is associated with a reduced microvascular function during adulthood. Thirty-four adults (34 ± 3 yr) from the Augusta Heart Study returned to participate in the present clinical observational study. Sirt1 was assessed in samples collected during both adulthood and participants' childhood (16 ± 3 yr), and data were divided based on childhood Sirt1 concentrations: <3 ng/dL (LowCS; n = 16) and ≥3 ng/dL (HighCS; n = 18). MVF was evaluated in all of the adults using laser-Doppler flowmetry coupled with three vascular reactivity tests: 1) local thermal hyperemia (LTH), 2) post-occlusive reactive hyperemia (PORH), and 3) iontophoresis of acetylcholine (ACh). The hyperemic response to LTH was significantly (P ≤ 0.044) lower in the LowCS than in the HighCS group. Similarly, the LowCS also exhibited an ameliorated (P ≤ 0.045) response to the PORH test and lower (P ≤ 0.008) vasodilation in response to iontophoresis of ACh when compared with the HighCS. Positive relationships were identified between childhood Sirt1 and all MVF reactivity tests (r≥0.367, P ≤ 0.004). Novel observations suggest that lower Sirt1 during childhood is associated with premature microvascular dysfunction in adulthood. These findings provide evidence that Sirt1 may play a critical role in microvascular function and have therapeutic potential for the prevention of age-associated vascular dysfunction in humans.NEW & NOTEWORTHY With a longitudinal cohort, novel observations from the present study demonstrate that individuals who had lower Sirt1 early in life exhibit premature microvascular dysfunction during adulthood and may be at higher risk to develop CVD. These results provide experimental evidence that Sirt1 may play an important role in microvascular function with age and represent a potential therapeutic target to prevent premature vascular dysfunction.

Reproducibility of Novel Indices of Reactive Hyperemia Using Laser Speckle Contrast Imaging

Post‐occlusive reactive hyperemia (PORH) is an indicator of microvascular function, but lack of standardization and reliability of measurement have limited its use clinically. The purpose of this study was to assess the intra‐ and inter‐day reliability of conventional and novel parameters of PORH using laser speckle contrast imaging (LSCI). Seventeen healthy adults (age = 24±3 years) completed three PORH bouts over two randomly assigned lab visits that were interspaced by 4–14 days. LSCI region of interest was a standardized 10 cm region below the antecubital fossa on the dominant ventral forearm. A 5‐min brachial artery occlusion period induced by inflating an arm cuff to 200 mmHg, preceded a 4‐min hyperemic period. LSCI flux was expressed as cutaneous vascular conductance (CVC; flux/mean arterial pressure). Reliability and reproducibility were assessed using intraclass correlation (ICC) and coefficient of variation (CV). Maximal flow (peak) and area under the curve (AUC) normalized to zero perfusion showed intra‐ and inter‐day reliability of ICC &gt; 0.70. Inter‐day ICC was lower when AUC was expressed as a function of resting flow (ICC=0.50) or biological zero (ICC=0.66). Time to maximal flow (TMF) had lower intra‐day (CV=12%) and inter‐day (CV=18%) reproducibility. When representing velocity (overshoot rate of change, ORC) within defined time ranges (5s, 10s, 15s, and 20s into hyperemia) as a piecewise function, the inter‐day reproducibility was &lt;11%. Thus, depending on data normalization, PORH using LSCI is a reliable method to assess microvascular function. TMF should be interpreted with caution, but an alternative temporal index may be the ORC.Support or Funding InformationThis research did not receive any specific grant from funding agencies in the public, commercial, or non‐profit sectors.Commonly examined post‐occlusive reactive hyperemia parameters are illustrated. Resting flow (RF), maximal flow (MF), time to maximal flow (TMF), amplitude of the MF normalized to RF and BZ (AMPRF and AMPBZ) and 4‐min post cuff‐deflation area under hyperemic curve (4‐min AUC) normalized to zero perfusion are shown. Time = 0 corresponds to cuff deflation. Magnified tracing at the top right shows the hyperemic response 30s post‐cuff deflation.Figure 1 Statistics for the PORH parameters are shown as mean ± SD, ICC, 95% limits of agreement, and coefficient of variation for the three PORH responses (VA, VB1, VB2). ICC values less than 0.5, between 0.5–0.75, between 0.75–0.9, and above 0.9 are classified as having poor, moderate, good, and excellent reliability. CV values less than 10%, between 10–25%, and above 25% are considered having good, moderate, and poor reproducibility. Descriptive Statistics (CVC) Reproducibility Statistics (CVC) Mean ± SD INTRADAY (VB1 &amp; VB2) INTERDAY (VA &amp; VB1) VA VB1 VB2 ICC (LOA) CV (%) ICC (LOA) CV (%) RF 0.62 ± 0.17 0.62 ± 0.14 0.60 ± 0.15 0.89 (0.73, 0.96) 6.47 0.89 (0.72, 0.96) 6.72 MF 2.41 ± 0.70 2.32 ± 0.56 2.35 ± 0.73 0.88 (0.70 0.95) 5.13 0.77 (0.48,0.91) 9.49 TMF 19.3 ± 5.68 19.0 ± 6.82 18.9 ± 5.11 0.65 (0.25, 0.86) 11.71 0.52 (0.06, 0.80) 17.75 4‐min AUC 282 ± 88.5 274 ± 70.4 262 ± 67.2 0.93 (0.79, 0.97) 4.88 0.73 (0.39, 0.89) 9.33 PI 300 ± 74.0 282 ± 62.6 285 ± 53.2 0.70 (0.34, 0.88) 10.74 0.51 (0.07, 0.79) 12.65 AMPRF 1.81 ± 0.60 1.71 ±0.46 1.75 ± 0.60 0.85 (0.64, 0.94) 6.65 0.66 (0.28, 0.86) 12.61 AMPBZ 2.18 ± 0.67 2.10 ± 0.51 2.13 ± 0.67 0.86 (0.66, 0.95) 5.53 0.75 (0.45, 0.90) 10.27 AUCRF 134 ± 60.1 125 ± 48.8 117 ± 40 0.88 (0.70, 0.95) 10.63 0.50 (0.04, 0.79) 16.64 AUCBZ 231 ±83.3 219 ± 63.2 207 ± 55.8 0.91 (0.74, 0.97) 6.46 0.66 (0.27, 0.86) 11.97 1‐min AUC 114 ± 34.0 112 ± 30.9 111 ± 32.2 0.94 (0.83, 0.98) 4.83 0.77 (0.47, 0.91) 9.70 AUC index 3.15 ± 0.53 3.06 ± 0.54 3.04 ± 0.39 0.84 (0.62, 0.94) 4.82 0.33 (−0.18, 0.69) 9.35 ORC5 0.37 ± 0.10 0.36 ± 0.10 0.35 ± 0.10 0.89 (0.72, 0.96) 6.95 0.73 (0.4, 0.89) 9.52 ORC10 0.21 ± 0.05 0.20 ± 0.04 0.20 ± 0.06 0.83 (0.58, 0.93) 6.33 0.71 (0.38, 0.89) 8.39 ORC15 0.15 ± 0.04 0.14 ± 0.03 0.15 ± 0.04 0.85 (0.64, 0.94) 5.13 0.74 (0.43, 0.90) 8.65 ORC20 0.11 ± 0.03 0.11 ± 0.03 0.11 ± 0.04 0.87 (0.69, 0.95) 4.83 0.69 (0.34, 0.88) 10.70 ORCMF 0.12 ± 0.05 0.12 ± 0.04 0.12 ± 0.05 0.74 (0.41, 0.90) 15.27 0.22 (−0.31, 0.63) 22.90

NIRS‐derived Microvascular Oxygen Saturation Kinetics Related to Skeletal Muscle Metabolic Rate

IntroductionSkeletal muscle tissue oxygen hemoglobin/myoglobin saturation (STO2) measured during post occlusive reactive hyperemia (PORH) provides a kinetic parameter (STO2 upslope (%/time)) that has increasingly been used as a measure of microvascular responsiveness. The magnitude of the oxygen saturation prior to cuff release (STO2 min) often correlates to STO2 upslope but the physiological variable associated with variability in STO2 min is most likely muscle metabolic rate (MR). This physiologic variable likely influences the rate of reperfusion after cuff release. The purpose of this study, therefore, was to isolate variables contributing to differences in STO2 upslope through their influence on STO2 min. Our hypothesis was that MR would significantly affect STO2 upslope.MethodsThe anterior antebrachium of twenty‐two (11 male, 11 female), 18–26 years, normoglycemic subjects was monitored continuously by near infrared spectroscopy during three upper limb PORH tests. Tissue oxygenation variables were determined prior to, during the cuff and for 2.5 min. post‐cuff release. MR was calculated in ml O2/100 g lean tissue/min and used both corrected and uncorrected for ATT (MRC). Body fat and abdominal adiposity (%) were quantified by dual energy‐ray absorptiometry. Forearm adipose tissue thickness (ATT) (3.32 + 1.43 mm, range 2.8–6.7 mm) was measured by ultrasound.ResultsSTO2 min and STO2 upslope were significantly negatively correlated (r=−0.47, P= 0.03) and both were significantly negatively correlated with MR (r = −0.75, P = &lt;0.001 and r = −0.52, P = 0.01, respectively). In a multiple, forward step‐wise regression analysis with a dependent variable of STO2 upslope and independent variables of ATT, MR or MRC, STO2min, and total body fat, only ATT entered the equation (R squared 0.334, P= 0.006); no other variable statistically added any independent predictive power to the regression equation.ConclusionsTo our knowledge, this is the first study to assess the effects of MR on NIRS STO2 upslope. In contrast to our hypothesis, MR did not affect STO2 upslope but ATT did. This finding suggests that ATT must be taken into account when assuming differences in STO2 upslope reflect differences in microvascular reactivity even in largely lean subjects.Support or Funding InformationAmerican Heart Association, Grant/Award Number: 0151183ZWheaton College Alumni Summer Research Support

Changes in Microvascular Reactivity and Systemic Vascular Resistance in Patients With Psoriasis

The aim: of this pilot study was to explore local blood flow in psoriatic plaques and normal skin before and after provocations known to alter cutaneous vascular resistance in order to test whether the increased flow was caused by a failure of normal vascular control processes in plaque skin and what association it has with cardiovascular parameters. Material and methods: 11 patients who had a diagnosis of psoriasis vulgaris were enrolled in the study. Cutaneous blood flow was recorded over plaque and clinically normal skin. 10 healthy sex and age matched subjects were selected as controls. Blood flow in psoriatic and normal skin was measured by a single- channel Laser Doppler blood flowmeter (Blood Flow meter, AD Instruments Ltd., Oxford, UK). Post-occlusive reactive hyperaemia was assessed on the plaque and non-plaque site. Cardiovascular parameters: heart rate, systolic and diastolic pressure, cardiac output, and vascular resistance were continuously monitored by a Finapres (FINAPRES Medical Systems, The Netherlands). Results: In patients, basal-LD flow was significantly higher in psoriatic skin compared to nonpsoriatic skin and significantly higher than in the controls. However, the post-occlusive hyperaemia test did not reveal significant differences between the patients and control subjects. Systemic vascular resistance was significantly lower in patients with psoriasis compared to healthy individuals. Conclusions: The results suggest that reduced microvascular resistance is associated with a significant increase in blood flow of psoriatic plaques and with lower systemic vascular resistance.

Enhanced Antioxidative Defense by Vitamins C and E Consumption Prevents 7-Day High-Salt Diet-Induced Microvascular Endothelial Function Impairment in Young Healthy Individuals.

This study aimed to examine whether the oral supplementation of vitamins C and E during a seven-day high salt diet (HS; ~14 g salt/day) prevents microvascular endothelial function impairment and changes oxidative status caused by HS diet in 51 (26 women and 25 men) young healthy individuals. Laser Doppler flowmetry measurements demonstrated that skin post-occlusive reactive hyperemia (PORH), and acetylcholine-induced dilation (AChID) were significantly impaired in the HS group, but not in HS+C+E group, while sodium nitroprusside-induced dilation remained unaffected by treatments. Serum oxidative stress markers: Thiobarbituric acid reactive substances (TBARS), 8-iso prostaglandin-F2α, and leukocytes’ intracellular hydrogen peroxide (H2O2) production were significantly increased, while ferric-reducing ability of plasma (FRAP) and catalase concentrations were decreased in the HS group. All these parameters remained unaffected by vitamins supplementation. Matrix metalloproteinase 9, antioxidant enzymes Cu/Zn SOD and glutathione peroxidase 1, and leukocytes’ intracellular superoxide production remained unchanged after the protocols in both HS and HS+C+E groups. Importantly, multiple regression analysis revealed that FRAP was the most powerful predictor of AChID, while PORH was strongly predicted by both FRAP and renin-angiotensin system activity. Hereby, we demonstrated that oxidative dis-balance has the pivotal role in HS diet-induced impairment of endothelial and microvascular function in healthy individuals which could be prevented by antioxidative vitamins consumption.

Assessment of tissue perfusion and vascular function in mice by scanning laser Doppler perfusion imaging

Post-occlusive reactive hyperemia (PORH) is a key feature of physiological vasomotion to appropriately match the supply/demand ratio of tissues. This adaptive mechanism is severely disturbed in endothelial dysfunction with a reduced flow-mediated dilation (FMD). Reduced PORH and FMD are powerful prognostic risk factors in cardiovascular diseases. While these parameters are frequently determined in human beings, comparable methods applicable to mouse models are sparse. We aimed to evaluate the applicability and accuracy of scanning laser Doppler perfusion imaging (LDPI) to measure PORH in the mouse hindlimb. Changes in mean perfusion in response to vasoactive drugs and PORH (assessed by scanning LDPI) were compared with changes in diameter and blood flow in the femoral artery, as assessed by high-resolution ultrasound. We found that the measured LDPI signal significantly correlated with changes of inflow into the femoral artery. Vasodilation induced by administration of nitroglycerine and acetylcholine increased vessel diameter, blood flow and mean perfusion, while vasoconstriction following administration of epinephrine decreased all three parameters. PORH was induced by temporal occlusion of the femoral artery with an external cuff. During occlusion, mean perfusion decreased to a condition of zero-perfusion and release of the cuff induced an immediate increase in blood flow that was followed by femoral artery dilation driving PORH/perfusion. Surgical removal of the femoral artery decreased mean perfusion to a zero-perfusion level and fully abolished PORH. Importantly, the measurement of the PORH response by scanning LDPI is highly reproducible as determined by repeated measurements and intra/interobserver variation analysis. Last, we found that the PORH response was dependent on nitric oxide synthase and cyclooxygenase and declined with age. Thus, we here provide novel and robust non-invasive methods to serially measure tissue perfusion at baseline and during physiological and pharmacological modulation of vasomotor tone in the hindlimb of mice. The application of these LDPI scanning and ultrasound-based methods may be useful for testing the effects of drugs affecting vasomotor function or future elucidation of mechanisms leading to vasomotor dysfunction in mice in vivo.

Assessing Renal Microvascular Reactivity by Laser Speckle-Contrast Imaging in Angiotensin-II-Treated Mice.

IntroductionThe kidney is one of the main organs affected by microvascular damage wrought by hypertension. We developed an approach to investigate renal microcirculatory disturbance in live mice by measuring post-occlusive reactive hyperemia (PORH), a reactivity test exploring endothelial and neuro-microvascular functioning. Laser speckle-contrast analysis (LASCA) assesses microvascular blood flow; it provides real-time images of spatial and temporal blood flow dynamics. We compared basal blood flow and PORH test between control and angiotensin-II-treated mice (Ang-II) to validate the model.ObjectiveThe study objective was to develop an approach to investigate renal microcirculation, and then to compare microvascular reactivity assessed on LASCA in control versus Ang-II mice.MethodsThirty 7-week-old wild-type C57BL/6J mice were allocated into two groups. One received angiotensin-II via osmotic minipumps (Ang-II; n=15); the other served as control (n=15). Basal blood flow was measured on LASCA. The PORH test was then performed in the two groups.ResultsControl mice had significantly lower basal renal microcirculatory flow, expressed in perfusion units (PU), than Ang-II-treated mice (1448 ± 96 vs 1703 ± 185 PU, respectively; P < 0.05). Peak flow was lower in controls than in Ang-II mice (1617±104 vs.1724 ± 205 PU, respectively; P=0.21). Control mice had significantly higher kidney PORH than Ang-II mice (8±3 vs 1±4%, respectively; P < 0.05).ConclusionWe developed an innovative technique to study renal microcirculation in mice. Ang-II-treated mice showed significantly higher basal blood flow than controls, while PORH was significantly higher in controls than in Ang-II mice.

Stable laser-Doppler flow-motion patterns in the human cutaneous microcirculation: Implications for prospective geroscience studies.

Microvascular function has been assessed by determining the rhythmic oscillations in blood flow induced by the vasomotion of resistance vessels. Although laser-Doppler flowmetry (LDF) allows simple, non-invasive evaluation of this flow-motion in the cutaneous microcirculation, the temporal and spatial reproducibility of such assessments remains unclear.In the present study, we investigated cutaneous flow-motion in three consecutive years in eight skin regions using LDF in six healthy young volunteers. The characteristic flow-motion frequency was determined using fast-Fourier transformation. Additionally, in two years a more traditional measure of microvascular reactivity, postocclusive reactive hyperemia (PORH) was evoked in the forearm after transient brachial artery occlusion (1-2-3 min) induced by cuff inflation.Well-defined flow-motion was found in six regions showing significant differences in frequency: the highest flow-motion frequency was found in the frontal and temporal regions (8.0 ± 1.1 and 8.5 ± 1.0 cycles/min, cpm, respectively, mean ± SD) followed by the scapular, infraclavicular and coxal regions (7.5 ± 1.3; 6.7 ± 1.1 and 6.5 ± 1.2 cpm, respectively). The lowest, stable flow-motion was found in the posterior femoral region (5.5 ± 1.0 cpm), whereas flow-motion was detectable only sporadically in the limbs. The region-dependent flow-motion frequencies were very stable within individuals either between the body sides, or among the three measurements, only the infraclavicular region showed a small difference (114 ± 17%∗, % of value in 1st year; ∗P < 0.05). However, PORH indices differed after 2-3 min occlusions significantly in consecutive years.We report that flow-motion frequencies determined from LDF signals show both region-specificity and excellent intra-individual temporal and spatial reproducibility suggesting their usefulness for non-invasive follow-up of microvascular reactivity.

The effect of ivabradine as part of standard therapy on vascular endothelial function and cardiac electrical instability in patients with post-infarction cardiosclerosis and heart failure

Aim. To reveal the equivalence of nebivolol replacement with ivabradine in the prevention of endothelial dysfunction and cardiac electrical instability in patients with heart failure with reduced ejection fraction (HFrEF).Material and methods. In current observational study, 126 patients with HFrEF in the postinfarction period were randomized into two groups for six-month treatment: group 1 (n=62) — standard therapy (acetylsalicylic acid 0,1 g/day, clopidogrel 75 mg/day, veroshpiron 50 mg/day, nebivolol 5 mg/day, perindopril 5 mg/day and rosuvastatin 20 mg/day; group 2 (n=66) — the same therapy with nebivolol replacement with ivabradine 10 mg/day. Initially and after 6 months, 24-hour Holter monitoring was performed, heart rate variability was determined. We also investigated endothelial dysfunction using the photoplethysmographic technique with post-occlusive reactive hyperemia (PORH) test.Results. The heart rate, the number of episodes and the duration of symptomatic and silent myocardial ischemia, total myocardial ischemia were significantly decreased in both groups (p&lt;0,001). The decrease of supraventricular extrasystole frequency in both groups had not statistical significance (p&gt;0,05). In both groups, after therapy, parameters of heart rate variability were improved with the parasympathetic predominance (p&lt;0,01). In both groups, the PORH test revealed the increase of brachial artery diameter (group 1 — 5,90Ѓ}3,15% and group 2 — 5,88Ѓ}1,82%) and pulse wave amplitude (group 1 — 1,81Ѓ}0,78 and group 2 — 1,73Ѓ}0,90 times), which indicates a trend towards an improvement in endothelial function. Intergroup comparisons did not reveal significant differences.Conclusion. Ivabradine is equivalent to nebivolol in preventing ventricular extrasystole and reducing heart rate, number of episodes of symptomatic and silent ischemia and the duration of total myocardial ischemia in patients with HFrEF. Ivabradine equivalently to nebivolol improves endothelial function and heart rate variability with reducing the sympathetic activity.