Severely impaired microvascular reactivity in diabetic patients with an acute coronary syndrome

Skin microvascular reactivity and subendocardial viability ratio in relation to dyslipidemia and signs of insulin resistance in non-diabetic hypertensive patients

OBJECTIVE

The aim of this study was to evaluate the influence of dyslipidemia and insulin resistance for the development of microvascular dysfunction in non-diabetic primary hypertension.

METHODS

Seventy-one patients with untreated primary hypertension were included. Skin microvascular reactivity was evaluated by laser Doppler fluxmetry with iontophoresis (acetylcholine, ACh and sodium nitroprusside, SNP) and heat-induced hyperemia. Myocardial microvascular function was estimated by the subendocardial viability ratio (SEVR) calculated from pulse wave analysis and applanation tonometry. Triglyceride x glucose (TyG index) and triglyceride/HDL cholesterol ratio were used as measurements of insulin resistance.

RESULTS

Skin microvascular dysfunction was associated with low HDL cholesterol, where Ach-mediated peak flux (r = .27, p = .025) and heat-induced peak flux (r = .29, p = .017) related to HDL cholesterol levels. ACh peak flux was inversely related to TG/HDL ratio (r = -.29, p = .016), while responses to local heating and SNP did not. SEVR did not relate to HDL and was unrelated to markers of insulin resistance. These findings were confirmed by multivariable analyses, including potential confounders.

CONCLUSIONS

Early microvascular dysfunction can be detected in non-diabetic hypertensive patients and is related to dyslipidemia and to signs of insulin resistance, thus predicting future cardiovascular risk.

Assessment of Microcirculation in the Type 2 Diabetic and Impaired Glucose Tolerance Feet of Elderly Men by CEUS

OBJECTIVE

To evaluate the foot microcirculation in type 2 diabetes mellitus (T2DM) and impaired glucose tolerance patients (IGT) with contrast-enhanced ultrasound (CEUS).

METHODS

The study included 37 patients with T2DM but without diabetic foot (DM group), 15 patients with impaired glucose tolerance (IGT group) and 10 elderly males with normal fasting blood glucose (FBS) and negative glucose tolerance tests (control group). Color Doppler flow imaging (CDFI) and CEUS were performed on the right foot great toes for detecting the blood perfusion performance. CEUS images were recorded and parameters of CDFI and flow time-intensity curves (TICs) were analyzed by the Student's t-test.

RESULTS

There was no significant difference in CDFI parameters pulse index and peak systolic blood flow velocity (PSV) among the three groups (P >0.05). Compared with control group, CEUS images of IGT and DM groups showed lower microvascular density and were pale. Peak intensity (PI) and area under time-intensity curve (AUC) in control, IGT and DM groups were decreased gradually (PI 46.36±10.96 vs 35.26±11.65 vs 28.15±7.94, P = 0.001, AUC 5.12±1.02 vs 3.25±1.60 vs 2.81±1.20, P = 0.001). The arrival times (AT) and time to peak (TTP) tended to be increased with the extension of DM course, but the difference was not statistically significant (AT, P = 0.260, TTP, P = 0.481).

CONCLUSION

CEUS, as a noninvasive and valuable technique, could detect the alterations in foot microcirculation of DM and IGT patients.

Effects of exenatide on microvascular reactivity in patients with type 2 diabetes and coronary artery disease: A randomized controlled study

OBJECTIVE

We studied the effect of the GLP-1RA exenatide on skin microvascular function in patients with T2DM and CAD.

METHODS

Thirty-five patients with T2DM, CAD, and HbA1C 42-86 mmol/mol were randomized to treatment with exenatide or conventional non-GLP-1-based therapy for 12 weeks. Skin microvascular function was examined in the forearm by LDF and iontophoretic application of acetyl choline and SNP, and by PORH at baseline and after 12 weeks. Blood samples for fasting plasma glucose, HbA1C, and lipid profile were collected.

RESULTS

At 12 weeks, patients on exenatide showed reductions in HbA1C (from 63.5 ± 13 to 60.7 ± 14 mmol/mol, p = .065), body weight (from 92.6 ± 16 to 89 ± 16 kg, p < .001), and systolic blood pressure (from 141 ± 13 to 134 ± 16 mm Hg, p < .05) as compared to the conventionally treated group. There were no significant changes in skin microvascular function between or within the two groups at follow-up.

CONCLUSIONS

Three months' daily treatment with the GLP-1RA exenatide in T2DM patients with CAD showed no significant effects on skin microvascular function or blood glucose control, while this study confirms a reduction in body weight and blood pressure by exenatide, as compared to conventional antidiabetic drug treatment.

Relationship of Sarcopenia with Microcirculation Measured by Skin Perfusion Pressure in Patients with Type 2 Diabetes

BACKGROUND

Few studies have examined the relationship of sarcopenia with the microcirculation. The current study investigated the relationship of sarcopenia with microcirculatory function, as assessed by skin perfusion pressure (SPP), in type 2 diabetes mellitus (T2DM) patients.

METHODS

In total, 102 T2DM patients who underwent SPP measurements and bioelectrical impedance analysis (BIA) were enrolled in this cross-sectional study. SPP was assessed using the laser Doppler technique. Sarcopenia was defined as low height-adjusted appendicular muscle mass (men, &lt;7 kg/m2; women, &lt;5.7 kg/m2) using BIA. We divided the participants into two groups based on SPP (≤50 and &gt;50 mm Hg), and an SPP below 50 mm Hg was considered to reflect impaired microcirculation.

RESULTS

Fourteen patients (13.7%) were diagnosed with impaired microcirculatory function of the lower limb based on SPP. The prevalence of sarcopenia in all subjects was 11.8%, but the percentage of patients with an SPP ≤50 mm Hg who had sarcopenia was more than triple that of patients with an SPP &gt;50 mm Hg (28.6% vs. 9.1%, P=0.036). A significant positive correlation was found between SPP and appendicular muscle mass adjusted for height (P=0.041 for right-sided SPP). Multiple logistic regression analysis showed that patients with sarcopenia had an odds ratio of 4.1 (95% confidence interval, 1.01 to 24.9) for having an SPP ≤50 mm Hg even after adjustment for confounding factors.

CONCLUSION

These results suggest that sarcopenia may be significantly associated with impaired microcirculation in patients with T2DM. Nonetheless, the small number of patients and wide CI require cautious interpretation of the results.

Individual cell motion in healthy human skin microvasculature by reflectance confocal video microscopy

OBJECTIVE

To describe upper dermal microvasculature of healthy human skin in terms of density and size of cutaneous blood vessels, leukocyte velocity, and leukocyte interactions with the endothelium.

METHODS

We used a reflectance confocal microscope, the VivaScope 1500, to acquire videos of individual cell motion.

RESULTS

We found no rolling leukocytes in the upper microvasculature of ten healthy subjects. We observed "paused" leukocytes, that is, leukocytes that temporarily stop, coinciding with the simultaneous stopping of the rest of the blood flow. We imaged more paused (median: 1.0 per subject) and adherent (1.5) leukocytes in the forearm than in the chest (median 0 paused and 0 adherent per subject) per 5 minutes of videos per body site. Leukocytes were paused for a median of 7 seconds in the forearm and 3 seconds in the chest, and we found no correlation between this parameter and the blood vessel or leukocyte size. We visualized blood flow change direction. Flowing leukocyte velocities followed a lognormal distribution and were on average higher in the chest (117 µm/s) than in the forearm (66 µm/s).

CONCLUSION

The proposed method and reported values in healthy skin provide new insights into intact human skin microcirculation.

Chronic Diabetes Complications: The Need to Move beyond Classical Concepts

Chronic-diabetes-related complications simultaneously compromise both the micro- and macrovascular trees, with target organs considered as the paradigm of large vessel injury also entailing microangiopathic changes. However, complications independent or partially independent from vascular damage are often overlooked. This includes neuronal dysfunction (e.g., retinal neurodegeneration), interstitial injury (e.g., tubulointerstitial disease), metabolic damage (e.g., in the heart and liver), and nonclassical conditions such as cognitive decline, impaired pulmonary function, or increased risk of cancer. In this scenario, researchers, endocrinologists and primary care physicians should have a holistic view of the disease and pay further attention to all organs and all potential clinical repercussions, which would certainly contribute to a more rational and integrated patient health care.

Influence of 8-Week Aerobic Training on the Skin Microcirculation in Patients with Ischaemic Heart Disease

Materials and Methods

In the study, 48 men took part with a stabilized and pharmacologically controlled ischaemic disease. The participants were randomly divided into two groups with 24 people in each of them. The research group participated in an aerobic march training. The march was taking place 3 times a week for 30-40 minutes over a period of 8 weeks. In the time of training, the subjects did not practise any other physical activity for 8 weeks. The measurement of skin microcirculation was done by using the laser Doppler flowmeter estimating the values of regular flow and the reactions provoked in response to occlusion and temperature. Signal frequency was also analysed which was received by means of laser Doppler flowmetry in the range from 0.01 to 2 Hz during the regular flow.

Results

During the first measurement in relation to the initial values, a decrease in body mass was noted by 2.21 kg on average as well as reduction of systolic and diastolic pressure by 10.4 mmHg and 3.68 mmHg, respectively. The regular flow (RF) increased after the training by 2.21%. The provoked reactions were as follows: hyperemic (PRHmax): an increase occurred by 8.76% and hyperthermic (THmax): an increase occurred by 5.38%. The time needed to achieve PRHmax was reduced by 42% and to achieve THmax, by 22%. The heart rhythm and the signal strength of neurogenic rhythm decreased by approximately 8% and 24%, respectively. The signal strength of endothelial rhythm increased by 19%. In the second measurement, a recourse was noted in the values of indicators under investigation, which were assuming values close to the initial ones. In the control group, the measurement values did not change significantly.

Conclusions

8 weeks of systematic aerobic training provides a significant improvement of endothelium functioning, expressed by reactivity improvement in skin microcirculation in patients suffering from ischaemic heart disease. It points to aerobic training as a nonpharmacological effective cardioprotective factor. The improvement effects of skin vascular bed functioning in the group of patients with IHD are impermanent, and they disappear after the period in which patients did not exercise physical activity.

Contactless Monitoring of Microcirculation Reaction on Local Temperature Changes

Assessment of skin blood flow is an important clinical task which is required to study mechanisms of microcirculation regulation including thermoregulation. Contactless assessment of vasomotor reactivity in response to thermal exposure is currently not available. The aim of this study is to show the applicability of the imaging photoplethysmography (IPPG) method to measure quantitatively the vasomotor response to local thermal exposure. Seventeen healthy subjects aged 23 ± 7 years participated in the study. A warm transparent compress applied to subject’s forehead served as a thermal impact. A custom-made IPPG system operating at green polarized light was used to monitor the subject’s face continuously and simultaneously with skin temperature and electrocardiogram (ECG) recordings. We found that the thermal impact leads to an increase in the amplitude of blood pulsations (BPA) simultaneously with the skin temperature increase. However, a multiple increase in BPA remained after the compress was removed, whereas the skin temperature returned to the baseline. Moreover, the BPA increase and duration of the vasomotor response was associated with the degree of external heating. Therefore, the IPPG method allows us to quantify the parameters of capillary blood flow during local thermal exposure to the skin. This proposed technique of assessing the thermal reactivity of microcirculation can be applied for both clinical use and for biomedical research.

Multi-domain analysis of microvascular flow motion dynamics in NAFLD

OBJECTIVE

To determine whether analysis of microvascular network perfusion using complexity-based methods can discriminate between groups of individuals at an increased risk of developing CVD.

METHODS

Data were obtained from laser Doppler recordings of skin blood flux at the forearm in 50 participants with non-alcoholic fatty liver disease grouped for absence (n = 28) or presence (n = 14) of type 2 diabetes and use of calcium channel blocker medication (n = 8). Power spectral density was evaluated and Lempel-Ziv complexity determined to quantify signal information content at single and multiple time-scales to account for the different processes modulating network perfusion.

RESULTS

Complexity was associated with dilatory capacity and respiration and negatively with baseline blood flux and cardiac band power. The relationship between the modulators of flowmotion and complexity of blood flux is shown to change with time-scale improving discrimination between groups. Multiscale Lempel-Ziv achieved best classification accuracy of 86.1%.

CONCLUSIONS

Time and frequency domain measures alone are insufficient to discriminate between groups. As cardiovascular disease risk increases, the degree of complexity of the blood flux signal reduces, indicative of a reduced temporal activity and heterogeneous distribution of blood flow within the microvascular network sampled. Complexity-based methods, particularly multiscale variants, are shown to have good discriminatory capabilities.

The interrelation of endothelial function and microvascular reactivity in different vascular beds, and risk assessment in hypertension: results from the Doxazosin-ramipril study

There are several non-invasive methods to study endothelial function, but their interrelation and association to cardiovascular risk have not been well evaluated. We studied macrovascular and microvascular endothelial function simultaneously in different vascular beds in relation to cardiovascular mortality risk (Systematic Coronary Risk Evaluation, SCORE) and hypertension induced cardiac organ damage, and their interrelationship. The study investigated 71 hypertensive patients by forearm post-ischemic flow-mediated vasodilation, pulse wave analysis (applanation tonometry) and beta 2-adrenoceptor agonist stimulation for changes in reflection index, skin microvascular reactivity by laser Doppler fluxmetry with iontophoresis and heat-induced hyperaemia, and coronary microvascular function by subendocardial viability ratio (derived from pulse wave analysis). Flow mediated vasodilation related inversely to SCORE (r =  0.34, P = 0.011). Adding microalbuminuria and pulse wave velocity strengthened the associations. Pulse wave reflection changes did not relate to SCORE. Skin microvascular reactivity related inversely to SCORE (peak flux change to sodium nitroprusside r =  0.29, P = 0.033, and to heating r =  0.31, P = 0.018). Subendocardial viability ratio did not relate to SCORE. Endothelial function indices showed no consistent relation to cardiac target organ damage. The agreement between the different methods for evaluating indices of macrovascular and microvascular endothelial function was weak. In conclusion, indices of macrovascular and microvascular endothelial function relate to cardiovascular mortality risk. Their use may improve cardiovascular risk prediction in hypertension. However, methods representing different vascular beds show little interrelationship and are not interchangeable, which may depend on different pathogenetic mechanisms representing different aspects of future cardiovascular risk.

Trial registry: NCT02901977

Feasibility of using thermal response to Ka band millimeter wave heating to assess skin blood flow

OBJECTIVE

Implementation of clinical guidelines for diagnosing peripheral artery disease will demand screening many millions of patients who are considered at-risk. This will require faster, easier screening technologies to identify patients with compromised blood flow to the extremities.

APPROACH

The feasibility of using surface temperature response to K_a band (26.5-40 GHz) near-field irradiation to assess skin blood flow was explored using an animal model. Ears of domestic rabbits were subjected to low-power continuous wave radio frequency heating from an open-ended waveguide (WR-28) at f  =  35 GHz. Three flow conditions were evaluated: (1) a baseline flow condition, (2) occluded flow and (3) reactive hyperemia. Surface temperatures were monitored continuously by means of an infrared thermography camera during each 2 min exposure.

MAIN RESULTS

Ensemble average results showed significant differences (p  <  .05) at exposure times 30, 60, 90 and 120 s between baseline and occluded conditions, and between baseline and reactive hyperemia conditions. The occluded condition (N  =  12) resulted in an average temperature increase of 21.4 °C  ±  3.9 after 2 min, compared with an average increase of 12.1 °C  ±  1.6 for baseline conditions (N  =  9) and 4.7 °C  ±  3.6 for post-occlusion/hyperemic conditions (N  =  8).

SIGNIFICANCE

Results are compared with the results of a simple two parameter mathematical model. These results suggest a method for non-invasive skin blood flow assessment to screen for peripheral artery disease and associated risk of cardiovascular events.

Diabetes, cardiovascular disease and the microcirculation

Cardiovascular disease (CVD) is the leading cause of mortality in people with type 2 diabetes mellitus (T2DM), yet a significant proportion of the disease burden cannot be accounted for by conventional cardiovascular risk factors. Hypertension occurs in majority of people with T2DM, which is substantially more frequent than would be anticipated based on general population samples. The impact of hypertension is considerably higher in people with diabetes than it is in the general population, suggesting either an increased sensitivity to its effect or a confounding underlying aetiopathogenic mechanism of hypertension associated with CVD within diabetes. In this contribution, we aim to review the changes observed in the vascular tree in people with T2DM compared to the general population, the effects of established anti-diabetes drugs on microvascular outcomes, and explore the hypotheses to account for common causalities of the increased prevalence of CVD and hypertension in people with T2DM.

The impact of cardiovascular co-morbidities and duration of diabetes on the association between microvascular function and glycaemic control

BACKGROUND

Good glycaemic control in type 2 diabetes (T2DM) protects the microcirculation. Current guidelines suggest glycaemic targets be relaxed in advanced diabetes. We explored whether disease duration or pre-existing macrovascular complications attenuated the association between hyperglycaemia and microvascular function.

METHODS

743 participants with T2DM (n = 222), cardiovascular disease (CVD = 183), both (n = 177) or neither (controls = 161) from two centres in the UK, underwent standard clinical measures and endothelial dependent (ACh) and independent (SNP) microvascular function assessment using laser Doppler imaging.

RESULTS

People with T2DM and CVD had attenuated ACh and SNP responses compared to controls. This was additive in those with both (ANOVA p < 0.001). In regression models, cardiovascular risk factors accounted for attenuated ACh and SNP responses in CVD, whereas HbA₁c accounted for the effects of T2DM. HbA₁c was associated with ACh and SNP response after adjustment for cardiovascular risk factors (adjusted standardised beta (β) -0.096, p = <0.008 and -0.135, p < 0.001, respectively). Pre-existing CVD did not modify this association (β -0.099; p = 0.006 and -0.138; p < 0.001, respectively). Duration of diabetes accounted for the association between HbA₁c and ACh (β -0.043; p = 0.3), but not between HbA₁c and SNP (β -0.105; p = 0.02).

CONCLUSIONS

In those with T2DM and CVD, good glycaemic control is still associated with better microvascular function, whereas in those with prolonged disease this association is lost. This suggests duration of diabetes may be a better surrogate for "advanced disease" than concomitant CVD, although this requires prospective validation.

The association between diabetes and dermal microvascular dysfunction non-invasively assessed by laser Doppler with local thermal hyperemia: a systematic review with meta-analysis

Background/Introduction

Diabetes and cardiovascular disease develop in concert with metabolic abnormalities mirroring and causing changes in the vasculature, particularly the microcirculation. The microcirculation can be affected in different parts of the body of which the skin is the most easily accessible tissue.

Purpose

The association between diabetes and dermal microvascular dysfunction has been investigated in observational studies. However, the strength of the association is unknown. Therefore we conducted a systematic review with meta-analysis on the association between diabetes and dermal microvascular dysfunction as assessed by laser Doppler/laser speckle contrast imaging with local thermal hyperaemia as non-invasive indicator of microvascular functionality.

Methods

PubMed and Ovid were  systematically searched for eligible studies through March 2015. During the first selection, studies were included if they were performed in humans and were related to diabetes or glucose metabolism disorders and to dermal microcirculation. During the second step we selected studies based on the measurement technique, measurement location (arm or leg) and the inclusion of a healthy control group. A random effects model was used with the standardised mean difference as outcome measure. Calculations and imputation of data were done according to the Cochrane Handbook.

Results

Of the 1445 studies found in the first search, thirteen cross-sectional studies were included in the meta-analysis, comprising a total of 857 subjects. Resting blood flow was similar between healthy control subjects and diabetes patients. In contrast, the microvascular response to local skin heating was reduced in diabetic patients compared to healthy control subjects [pooled effect of −0.78 standardised mean difference (95% CI −1.06, −0.51)]. This effect is considered large according to Cohen’s effect size definition. The variability in effect size was high (heterogeneity 69%, p < 0.0001). However, subgroup analysis revealed no difference between the type and duration of diabetes and other health related factors, indicating that diabetes per se causes the microvascular dysfunction.

Conclusion

Our meta-analysis shows that diabetes is associated with a large reduction of dermal microvascular function in diabetic patients. The local thermal hyperaemia methodology may become a valuable non-invasive tool for diagnosis and assessing progress of diabetes-related microvascular complications, but standardisation of the technique and quality of study conduct is urgently required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0487-1) contains supplementary material, which is available to authorized users.