Brachial flow-mediated vasodilator responses in population-based research: methods, reproducibility and effects of age, gender and baseline diameter

Rho-kinase inhibition reduces systolic blood pressure and forearm vascular resistance in healthy older adults: a double-blind, randomized, placebo-controlled pilot study

Rho-kinase has been implicated in the development of hypertension in preclinical studies and may contribute to age-related blood pressure elevation. This study tested the hypothesis that Rho-kinase contributes to elevated systolic blood pressure (SBP) in healthy older adults. Young (18-30 years, 6F/6M) and older (60-80 years, 7F/6M) adults were enrolled in a double-blind, placebo-controlled crossover study using intravenous fasudil infusion to inhibit Rho-kinase. Fasudil lowered SBP in older adults compared to placebo (saline) (2-h post-infusion: 125 ± 4 vs. 133 ± 4 mmHg, P < 0.05), whereas fasudil had no impact on SBP in young adults. Immediately following fasudil infusion, there was a transient reduction in mean arterial pressure (MAP) in young adults that was no longer evident 1-h post-infusion. In older adults, MAP remained lower throughout the fasudil visit compared to placebo (2-h post-infusion: 93 ± 3 vs. 100 ± 3 mmHg, P < 0.05) such that age-related differences in SBP and MAP were abolished. Aortic stiffness (carotid-femoral pulse wave velocity) was not altered by fasudil when central MAP was included as a covariate in analyses. Fasudil reduced forearm vascular resistance in older (2-h post-infusion: 3.3 ± 0.4 vs. 4.8 ± 0.6 mmHg/ml/min, P < 0.05) but not young (4.0 ± 0.6 vs. 3.8 ± 0.5 mmHg/ml/min) adults, which was accompanied by an increase in brachial artery diameter only in older adults. Brachial artery flow-mediated dilation was not affected by fasudil in either group. These findings indicate that Rho-kinase inhibition reduces SBP in healthy older but not young adults, which is associated with a concomitant reduction in forearm vascular resistance.

Acute Effects of Cocoa Flavanols on Blood Pressure and Peripheral Vascular Reactivity in Type 2 Diabetes Mellitus and Essential Hypertension

Background: Type 2 diabetes mellitus (T2DM) is associated with a high risk of vascular complications. Interestingly, cocoa flavanols (CF) can exert beneficial vascular effects in non-diabetic subjects. However, these effects have only been scarcely studied in T2DM. Therefore, we performed a study to assess the effects on vascular reactivity of a single dose of CF (790 mg) in T2DM and whether certain antihypertensive drugs may modulate these effects. Methods: 24 non-diabetic and 11 T2DM subjects were studied in a cross-over design. Fasting blood samples, blood pressure (BP), and arterial vasoreactivity (flow-mediated dilation) were assessed before and 70 min after capsule ingestion. Muscle microvascular reactivity was only assessed after capsule ingestion. Age, waist-to-hip ratio, BP at baseline, and the use of antihypertensive drugs were regarded as covariates in a mixed models analysis. Results: CF ingestion did not affect any parameter. However, independent of the type of capsules ingested, a decrease in diastolic BP by 3 mmHg (95% CI: −4.0; −2.0) and an increase in the change in brachial artery diameter (pre vs. post occlusion) by 0.06 mm (95% CI: 0.01; 0.12) were detected in the non-diabetic group, while they remained unchanged in the T2DM group. Conclusion: No beneficial effects of CF were detected on vascular reactivity parameters in T2DM and non-diabetic participants.

Carotid artery vasoreactivity correlates with abdominal aortic vasoreactivity in young healthy individuals but not in patients with abdominal aortic aneurysm

Background

Sympathetic stimulation of central arteries, such as coronary and carotid arteries, cause vasodilation in healthy subjects, but vasoconstriction in those with increased cardiovascular risk. This study compared vasoreactivity to sympathetic stimulation between abdominal aorta and carotid artery in healthy young individuals (young group, n = 20), in patients with abdominal aortic aneurysm (AAA group, n = 20) and in a healthy older group, age- and gender matched with AAA group (matched group, n = 18).

Method

All subjects underwent cold pressor test, while performing concomitantly duplex ultrasound of abdominal aorta and carotid artery vasoreactivity. Observer-independent software was used to analyze and calculate magnitude and timing of maximum vasodilation or vasoconstriction. Pearson's correlation coefficient was calculated to investigate vasoreactivity between arteries.

Results

Carotid artery reactivity [Interquartile range 25%, Interquartile range 75%] did not significantly differ between the young, matched and AAA group (3.5% [1.4, 4.7], 2.6% [2.0, 4.1] and 2.2% [-1.9, 3.7], respectively, p = 0.301). Abdominal aortic responsiveness demonstrated larger differences between young (4.9% [-0.2, 8.4]), matched (3.3% [-2.5, 4.4]) and individuals with AAA (0.5% [-3.9, 4.1], p = 0.059). Pooled analysis showed a significant correlation between carotid and abdominal aortic vasoreactivity (r = 0.444, p = 0.001). Subgroup analyses demonstrated significant correlation between both arteries in young (r = 0.636, p = 0.003), but not matched (r = −0.040, p = 0.866) or AAA group (r = 0.410, p = 0.129).

Conclusions

Sympathetic stimulation induces powerful vasodilation of the carotid artery and abdominal aorta, which is significantly correlated in healthy individuals. No such correlation is present in abdominal aortic aneurysm patients. This suggests the aneurysm alters local abdominal aorta vasoreactivity, but not the carotid artery.

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Vasoreactivity is significantly correlated between carotid and abdominal aorta.

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Presence of abdominal aneurysm was associated with local impaired vasoreactivity.

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Abdominal aorta demonstrates a stronger vasoreactivity than the carotid artery.

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Vasoreactivity of the carotid artery did not differ between groups.

Effects of resistance training on endothelial function: A systematic review and meta-analysis

BACKGROUND AND AIMS

The effects of resistance training on flow-mediated dilation (FMD), which has been the gold standard non-invasive assessment of endothelial function and is associated with the risk of cardiovascular events, are not well known. We conducted a systematic review to analyze the effects of resistance training on FMD.

METHODS

We searched Pubmed, Embase, CINAHL, SPORTDiscuss, Scopus, Web of Science and PEDro databases for studies that met the following criteria: (a) randomized controlled trials of resistance exercise with a comparative non-exercise group or contralateral untrained limb in adults and/or elderly; (b) studies that measured post-occlusion brachial artery FMD by ultrasonography, before and after intervention. Mean differences (MDs) with 95 % confidence interval (95 % CI) were calculated using an inverse variance method with a random effects model.

RESULTS

Twenty-three studies were included in the meta-analysis (n = 785 participants; 53 % females). Resistance training on FMD responses showed a favorable result for the resistance training group (n = 366) compared to the control group (n = 358) (MD 2.39, 95%CI 1.65, 3.14; p<0.00001). Subgroup analysis indicated favorable results for the dynamic resistance training (n = 545; MD 2.12, 95 % CI 1.26, 2.98; p<0.00001) and isometric handgrip training (n = 179; MD 3.32, 95 % CI 1.68, 4.96; p<0.0001) compared to the control group. The effect of resistance training on FMD responses was also favorable regardless of the condition of the participants (Healthy [n = 261]: MD 2.11, 95 % CI 1.04, 3.18; p<0.0001; Cardiovascular disease [n = 310]: MD 2.89, 95 % CI 0.88, 4.90; p = 0.005; metabolic disease [n = 153]: MD 2.40, 95 % CI 1.59, 3.21; p<0.00001).

CONCLUSIONS

Resistance training improves FMD in healthy individuals and patients with cardiovascular and metabolic diseases.

Serum Non-Esterified Fatty Acids, Carotid Artery Intima-Media Thickness and Flow-Mediated Dilation in Older Adults: The Cardiovascular Health Study (CHS)

Backgrounds and aims: Elevated common carotid artery intima-media thickness (carotid IMT) and diminished flow-mediated dilation (FMD) are early subclinical indicators of atherosclerosis. Serum total non-esterified fatty acid (NEFA) concentrations have been positively associated with subclinical atherosclerosis. The relations between individual NEFA, carotid IMT and FMD have as yet to be assessed. Methods: We investigated the associations between fasting serum individual NEFA, carotid IMT and FMD among Cardiovascular Health Study (CHS) participants with (n = 255 for carotid IMT, 301 for FMD) or without (n = 1314 for carotid IMT, 1462 for FMD) known atherosclerotic cardiovascular disease (ASCVD). Using archived samples (fasting) collected from 1996-1997 (baseline), 35 individual NEFAs were measured using gas chromatography. Carotid IMT and estimated plaque thickness (mean of maximum internal carotid IMT) were determined in 1998-1999. FMD was measured in 1997-1998. Linear regression adjusted by the Holm-Bonferroni method was used to assess relations between individual NEFA, carotid IMT and FMD. Results: In multivariable adjusted linear regression models per SD increment, the non-esterified trans fatty acid conjugated linoleic acid (trans-18:2 CLA) was positively associated with carotid IMT [β (95% CI): 44.8 (19.2, 70.4), p = 0.025] among participants with, but not without, ASCVD [2.16 (-6.74, 11.5), p = 1.000]. Non-esterified cis-palmitoleic acid (16:1n-7c) was positively associated with FMD [19.7 (8.34, 31.0), p = 0.024] among participants without, but not with ASCVD. No significant associations between NEFAs and estimated plaque thickness were observed. Conclusions: In older adults, serum non-esterified CLA and palmitoleic acid were positively associated with carotid IMT and FMD, respectively, suggesting potential modifiable biomarkers for arteriopathy.

Reliability of the hyperaemic response to passive leg movement in young, healthy women

NEW FINDINGS

What is the central question of this study? This is the first study to assess the day-to-day reliability of passive leg movement-induced hyperaemia (PLM-H), an index of lower-limb microvascular function, in young, healthy women. What is the main finding and its importance? Passive leg movement-induced hyperaemia demonstrated good day-to-day reliability, comparable to other common indices of endothelial function, supporting the use of PLM-H to assess lower-limb microvascular function in women.

ABSTRACT

Passive leg movement-elicited hyperaemia (PLM-H) provides an index of lower-limb microvascular function. However, there is currently limited information regarding the reliability of PLM-H and no reliability information specific to women. The purpose of this study was to determine the reliability of PLM-H in women on two separate days. Seventeen young, healthy women [22 ± 3 years old (mean ± SD)] participated in two identical visits including three trials of PLM. Using duplex ultrasound, PLM-H was characterized by six indices: peak leg blood flow (LBF) and vascular conductance (LVC), peak change above baseline (Δpeak) for LBF and LVC, and area under the curve above baseline (AUC) during the first 60 s of PLM for LBF and LVC. The results demonstrated good day-to-day reliability of PLM-H characterized as peak LBF [r = 0.84, P < 0.001; intraclass correlation coefficient (ICC) = 0.84; coefficient of variation (CV) = 13.2%], peak LVC (r = 0.82, P < 0.001; ICC = 0.79; CV = 14.4%), Δpeak LBF (r = 0.83, P < 0.001; ICC = 0.82; CV = 17.8%) and Δpeak LVC (r = 0.83, P < 0.001; ICC = 0.80; CV = 16.5%). Characterization of PLM as AUC demonstrated moderate day-to-day reliability: AUC LBF (r = 0.71, P < 0.05; ICC = 0.70; CV = 31.2%) and AUC LVC (r = 0.78, P < 0.001; ICC = 0.74; CV = 27.1%). In conclusion, this study demonstrates that PLM-H has good reliability as an index of microvascular function; however, characterization of PLM-H as peak, Δpeak LBF and LVC is more reliable than AUC.

Age- and sex-related profiles for macro, macro/micro and microvascular reactivity indexes: Association between indexes and normative data from 2609 healthy subjects (3-85 years)

Vascular reactivity (VR), defined as blood vessels’ capability to actively modify the diameter and flow resistances can be non-invasively assessed analyzing vascular response to forearm occlusion. Several VR indexes can be quantified: (i) ´microvascular´, which consider variables that depend almost exclusively on changes in distal resistances, (ii)´ macrovascular´, that evaluate the changes in brachial artery (BA) diameter, adjusting for blood flow stimulus, and (iii) ´macro/micro´, whose values depend on the micro and macrovascular response without discriminating each one´s contribution. VR indexes could not be associated. Many VR indexes have been used without availability of adequate normative data (reference intervals, RIs). Aims: (1) to evaluate macro, macro/micro and micro VR indexes obtained in a cohort of healthy children, adolescents and adults, (2) to evaluate the association between VR indexes, (3) to determine the need for age and/or sex-specific RIs, and (4) to define RIs for VR indexes. Methods: Ultrasound (B-mode/Doppler) and automatic computerized analysis were used to assess BA diameter, blood flow velocity and distal resistances, at rest and in conditions of decreased and increased blood flow. Macro, macro/micro and micro VR indexes were quantified (n = 3619). RIs-subgroups were defined according to European Reference Values for Arterial Measurements Collaboration Group (n = 1688, 3–84 years) and HUNT3-Fitness Study Group (n = 2609, 3–85 years) criteria. Mean value and standard deviation equations were obtained for VR indexes. The need for age or sex-specific RIs was analyzed. Percentile curves were defined and data were compared with those obtained in other populations. Conclusion: Macro and macro/micro VR indexes showed no association (or it was very weak) with microvascular indexes. Age- and sex-related profiles and RIs for macro, macro/micro and micro VR indexes were defined in a large population of healthy subjects (3–85 y). Equations for mean, standard deviation and percentiles values (year-to-year) were included in text and spreadsheet formats.

Reference Intervals for Brachial Artery Flow-Mediated Dilation and the Relation With Cardiovascular Risk Factors

[Figure: see text].

Brachial Flow-Mediated Dilation and Risk of Atrial Fibrillation in Older Adults: The Cardiovascular Health Study

Background

Endothelial dysfunction is associated with common risk factors for AF and has been implicated in the pathophysiology of atrial fibrillation (AF) through a variety of mechanisms. We determined the prospective association of brachial flow-mediated dilation (FMD) with incident AF among older adults.

Methods

We included 2027 Cardiovascular Health Study participants (mean age=78.3 years, male=39%, Black=17%) who underwent brachial FMD measurement at the 1997 to 1998 clinic visit. Incident AF was ascertained by study electrocardiograms, hospital discharge diagnosis coding and Medicare claims data. Cox regression models were used to examine the association between FMD and incident AF.

Results

We identified 754 incident of AF cases (37%) over a median follow-up of 11.0 years. After adjusting for age, sex, race, height, weight, cardiovascular disease, cigarette smoking, hypertension, diabetes, kidney function, c-reactive protein, physical activity, alcohol consumption, and statins, the risk of AF did not differ according to brachial FMD response (4th vs 1st quartile hazard ratio (HR)=1.01, 95% confidence interval (CI): 0.81, 1.26; per FMD unit increment HR=1.01, 95% CI: 0.97, 1.05).

Conclusion

We found no relationship between brachial FMD and the risk of developing AF in this elderly cohort. Our findings suggest that the utility of brachial FMD as a risk marker for AF in older individuals is minimal.

Increased Platelet Aggregation in Children and Adolescents with Sleep-disordered Breathing

Rationale: Sleep-disordered breathing (SDB) is associated with increased vascular resistance in children and adults. Persistent increased vascular resistance damages vascular endothelial cells-a marker of which is increased platelet activation.Objectives: This study compared whole-blood impedance platelet aggregation in children with clinically diagnosed SDB warranting adenotonsillectomy and healthy control subjects.Methods: Thirty children who had SDB warranting intervention clinically diagnosed by experienced pediatric otolaryngologists were recruited from adenotonsillectomy waitlists, and 20 healthy children from the community underwent overnight polysomnography to determine SDB severity (obstructive apnea-hypopnea index). Snoring frequency was collected from parents. In the morning, a fasting blood sample was taken, and whole-blood platelet aggregation was measured.Measurements and Main Results: Children with SDB exhibited increased platelet aggregation to TRAP (thrombin receptor-activating peptide) (children with SDB = 114.8 aggregation units [AU] vs. control subjects = 98.0 AU; P < 0.05) and COL antibody (96.7 vs. 82.2 AU; P < 0.05) and an increased trend in ADP antibody (82.3 vs. 69.2 AU; P < 0.07) but not aspirin dialuminate (82.1 vs. 79.5 AU; P > 0.05). No significant association was observed between either the obstructive apnea-hypopnea index and any aggregation parameter, but parental report of snoring was positively associated with TRAP aggregation (Kendall's τ-c = 0.23; P < 0.05).Conclusions: The finding of increased platelet aggregation is consistent with endothelial damage. This suggests that the profile of cardiovascular changes noted in adults with SDB may also occur in children with SDB.

Hourly staircase sprinting exercise "snacks" improve femoral artery shear patterns but not flow-mediated dilation or cerebrovascular regulation: a pilot study

Healthy males (n = 10; age: 24 ± 4 years; body mass index: 24 ± 2 kg·m^-2) completed 2 randomized conditions separated by ≥48 h involving 6-8.5 h of sitting with ("stair snacks") and without (sedentary) hourly staircase sprint interval exercise (∼14-20 s each). Resting blood flow and shear rates were measured in the femoral artery, internal carotid artery, and vertebral artery (Duplex ultrasound). Flow-mediated dilation (FMD) was quantified as an index of peripheral endothelial function in the femoral artery. Neurovascular coupling (NVC; regional blood flow response to local increases in cerebral metabolism) was assessed in the posterior cerebral artery (transcranial Doppler ultrasound). Femoral artery hemodynamics were higher following the active trial with no change in the sedentary trial, including blood flow (+32 ± 23% vs. -10 ± 28%; P = 0.015 and P = 0.253, respectively), vascular conductance (+32 ± 27% vs. -15 ± 26%; P = 0.012 and P = 0.098, respectively), and mean shear rate (+17 ± 8% vs. -8 ± 28%; P = 0.004 and P = 0.310, respectively). The change in FMD was not different within or between conditions (P = 0.184). Global cerebral blood flow (CBF), conductance, shear patterns, and NVC were not different within or between conditions (all P > 0.05). Overall, exercise "stair snacks" improve femoral artery blood flow and shear patterns but not peripheral (e.g., FMD) or cerebral (e.g., CBF and NVC) vascular function following prolonged sitting. The study was registered at ClinicalTrials.gov (NCT03374436). Novelty: Breaking up 8.5 h of sitting with hourly staircase sprinting exercise "snacks" improves resting femoral artery shear patterns but not FMD. Cerebral blood flow and neurovascular coupling were unaltered following 6 h of sitting with and without hourly exercise breaks.

Nonalcoholic Fatty Liver Disease-Evidence for a Thrombophilic State?

Nonalcoholic fatty liver disease is the leading cause of liver disease worldwide. It has expansive extrahepatic morbidity and mortality including increased rates of both cardiovascular disease and venous thromboembolism. Derangements in primary, secondary and tertiary hemostasis are found in nonalcoholic fatty liver disease independent of those ascribed to end-stage liver disease. The abnormalities across all stages of hemostasis explain the increased rates of clinically relevant thrombotic events, including pulmonary embolism, deep vein thrombosis and portal vein thrombosis, which on an epidemiologic basis appears to be independent of obesity and other traditional venous thromboembolic risk factors. However, given the complex interaction between obesity, body composition and nonalcoholic fatty liver disease and the potential for exercise to benefit all three, more research is needed to further define the role of each in contributing to the prohemostatic state of nonalcoholic fatty liver disease in order to improve patient oriented outcomes.

Endothelial dysfunction and the risk of heart failure in a community-based study: the Multi-Ethnic Study of Atherosclerosis

Aims

We aimed to investigate the association between endothelial dysfunction, assessed by brachial flow‐mediated dilation (FMD), and the incidence of heart failure (HF) in the community‐based Multi‐Ethnic Study of Atherosclerosis.

Methods and results

Brachial artery FMD was measured in a nested case‐cohort sample including 3496 of 6814 Multi‐Ethnic Study of Atherosclerosis participants without prevalent cardiovascular disease (mean age 61 years, 50% women). Multivariable probability‐weighted Cox proportional hazards analysis was used to examine the association between FMD and incident HF. We also investigated the association between FMD and HF with reduced vs. preserved ejection fraction [HFrEF (left ventricular ejection fraction <45%) vs. HFpEF (left ventricular ejection fraction ≥45%)]. During follow‐up (median 12 years), 149 participants developed incident HF (incidence rate 3.7 events per 1000 person years). There were 56 HFrEF and 69 HFpEF events (incidence rates 1.4 and 1.7 events per 1000 person years, respectively). In multivariable models adjusted for established HF risk factors (age, sex, race/ethnicity, body mass index, systolic blood pressure, antihypertensive treatment, heart rate, diabetes mellitus, history of myocardial infarction, current smoker, and former smoker status), individuals in the highest quartile of FMD (reflecting better endothelial function) had a lower HF risk compared with individuals in the lowest quartile [hazard ratio 0.53, 95% confidence interval (CI) 0.31–0.95]. Lower risk according to higher FMD was particularly evident for HFrEF, but not for HFpEF (hazard ratio per standard deviation increase 0.79, 95% CI 0.64–0.97 vs. 0.99, 95% CI 0.78–1.26, respectively). Results remained similar after adjustment for baseline natriuretic peptide levels. The addition of FMD to established HF risk factors generally rendered no or only modest improvement in C‐statistics [C‐statistics for model with established HF risk factors: 0.774, and with the addition of FMD: 0.776 (delta C 0.002, 95% confidence interval −0.002 to 0.006)].

Conclusions

Endothelial dysfunction was independently associated with HF in this community cohort, suggesting a pathophysiological contribution of endothelial function to the development of HF, in particular HFrEF. However, the value of FMD measurements for HF risk prediction seems limited.

Effects of Low-Fat and High-Fat Meals, with and without Dietary Fiber, on Postprandial Endothelial Function, Triglyceridemia, and Glycemia in Adolescents

The consumption of fiber-rich foods may negate the deleterious effects of high-fat meals on postprandial triglyceridemia and endothelial function. Despite supportive data in adults, little is known about the effects of high-fat and high-fiber foods on cardiovascular health parameters in pediatric populations. In this crossover trial, male and female adolescents (n = 10; 14.1 + 2.6 years; range 10–17 years) consumed (1) low-fat, low-fiber, (2) low-fat, high-fiber, (3) high-fat, low-fiber, and (4) high-fat, high-fiber breakfast meals in randomized order, each following an overnight fast. Baseline and 4 h post-meal blood was obtained for determination of glucose, insulin and triglyceride concentrations. Endothelial function was assessed via brachial artery flow-mediated dilation (FMD). Postprandial FMD was not significantly changed after any meal. However, regression analyses revealed a significant inverse relationship between the change in 4 h triglyceride concentration and change in 4 h FMD for the high-fat, low-fiber meal (β = −0.087; 95% CI = −0.138 to −0.037; p = 0.001) that was no longer significant in the high-fat, high-fiber meal (β = −0.044; 95% CI = −0.117 to 0.029; p = 0.227). Interpretation of these analyses must be qualified by acknowledging that between-meal comparison revealed that the two regression lines were not statistically different (p = 0.226). Addition of high-fiber cereal to the high-fat meal also reduced 4 h postprandial triglyceride increases by ~50% (p = 0.056). A high-fiber breakfast cereal did not attenuate postprandial glucose and insulin responses after consumption of a low-fat meal. While further work is needed to confirm these results in larger cohorts, our findings indicate the potential importance of cereal fiber in blunting the inverse relationship between postprandial hypertriglyceridemia and FMD after consumption of a high-fat meal in adolescents.

Subclinical Markers of Cardiovascular Disease Among Police Officers: A Longitudinal Assessment of the Cortisol Awakening Response and Flow Mediated Artery Dilation

OBJECTIVE

To examine the association of the cortisol awakening response (CAR) with change in brachial artery flow-mediated dilation (FMD%) in police officers over a 7-year period.

METHODS

Baseline CAR was obtained from four saliva samples taken 15 minutes apart immediately after awakening. Analysis of covariance was used to compare the change in FMD% (FMD%Follow-up-FMD%Baseline) across tertiles of area under the cortisol curve with respect to increase (AUCI). Regression analysis was use to assess trend.

RESULTS

Officers (n = 172; 81% men) had a mean ± SD age of 41 ± 7.6 years. Men in the lowest AUCI tertile (ie, atypical waking cortisol pattern) had a significantly larger 7-year mean decline in FMD% (mean ± SE: -2.56 ± 0.64) compared with men in the highest tertile (-0.89 ± 0.69) (P = 0.0087).

CONCLUSIONS

An awakening cortisol AUCI predicted worsening of FMD% approximately 7 years later among male officers.

The Role of Inflammation in the Endothelial Dysfunction in a Cohort of Pediatric Patients With Inflammatory Bowel Disease

OBJECTIVES

Chronic inflammation plays a central role in the etiology of endothelial damage. Endothelial dysfunction (ED) is the inability of the artery to dilate in response to an endothelial stimulus. We assessed the ED by measuring the reactive hyperaemia index (RHI) and the flow-mediated dilation (FMD) in a cohort of pediatric patients affected by inflammatory bowel disease (IBD) and comparing these parameters to a group of healthy controls (HC).

METHODS

Forty-one patients were consecutive enrolled. ED was evaluated by both the plethysmographic RHI method and the measurement of the FMD of brachial artery after occlusion of the blood flow. Differences between patients and controls were assessed by the Mann-Whitney test. In each patient with IBD, the main inflammation markers were detected and correlated to RHI and FMD by a linear regression test.

RESULTS

We enrolled 26 (59%) patients with IBD and 18 (41%) HC. When comparing FMD value at diagnosis it was significantly lower in IBD patients than in HC (P = 0.04). This result was confirmed at follow-up, when this difference became even more significant (P = 0.004). A significant indirect correlation was found between FMD and fecal calprotectin (r: 0.17; P = 0.04). No differences were found when comparing RHI.

CONCLUSIONS

Our results suggest that inflammation could lead to ED assessed by ultrasound FMD. These data were not confirmed by RHI; however, this could be due to the lack of a standardized pediatric cut-off. More studies are necessary to confirm our data.

Expert consensus and evidence-based recommendations for the assessment of flow-mediated dilation in humans

Endothelial dysfunction is involved in the development of atherosclerosis, which precedes asymptomatic structural vascular alterations as well as clinical manifestations of cardiovascular disease (CVD). Endothelial function can be assessed non-invasively using the flow-mediated dilation (FMD) technique. Flow-mediated dilation represents an endothelium-dependent, largely nitric oxide (NO)-mediated dilatation of conduit arteries in response to an imposed increase in blood flow and shear stress. Flow-mediated dilation is affected by cardiovascular (CV) risk factors, relates to coronary artery endothelial function, and independently predicts CVD outcome. Accordingly, FMD is a tool for examining the pathophysiology of CVD and possibly identifying subjects at increased risk for future CV events. Moreover, it has merit in examining the acute and long-term impact of physiological and pharmacological interventions in humans. Despite concerns about its reproducibility, the available evidence shows that highly reliable FMD measurements can be achieved when specialized laboratories follow standardized protocols. For this purpose, updated expert consensus guidelines for the performance of FMD are presented, which are based on critical appraisal of novel technical approaches, development of analysis software, and studies exploring the physiological principles underlying the technique. Uniformity in FMD performance will (i) improve comparability between studies, (ii) contribute to construction of reference values, and (iii) offer an easy accessible and early marker of atherosclerosis that could complement clinical symptoms of structural arterial disease and facilitate early diagnosis and prediction of CVD outcomes.

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Hypertension with primary aldosteronism is associated with increased carotid intima-media thickness and endothelial dysfunction

Patients with primary aldosteronism induced hypertension are more likely to experience cardiovascular events compared to patients with essential hypertension. Primary aldosteronism may therefore have distinct adverse effects on cardiovascular structure and function, independent of hypertension. However, current data on such effects of primary aldosteronism are conflicting. The aim of the present study was to investigate the influence of primary aldosteronism on vascular structure and endothelial function, using intima‐media thickness as a vascular remodeling index and flow‐mediated dilation as a functional parameter. In total, 70 participants were recruited from patients with resistant hypertension. Twenty‐nine patients diagnosed with primary aldosteronism and 41 patients with essential hypertension were prospectively enrolled. Primary aldosteronism was due to aldosterone‐producing adenoma in 10 cases and due to idiopathic adrenal hyperplasia in 19 cases. All patients underwent ultrasound of the common carotid intima‐media thickness and flow‐mediated dilation of the brachial artery. Primary aldosteronism patients had significantly lower flow‐mediated dilation (3.3 [2.4‐7.4] % vs 14.7 [10.3‐19.9] %, P < 0.01) and significantly higher carotid intima‐media thickness (0.9 [0.7‐1.0] mm vs 0.8 [0.6‐0.9] mm, P = 0.02) compared to patients with essential hypertension. These differences remained significant after adjusting for age, sex, diabetes mellitus, 24‐hours systolic blood pressure, and smoking (P < 0.01). No differences in either outcome were observed between the adenoma and adrenal hyperplasia groups (both P > 0.05). Hypertensive patients with hyperaldosteronism appear to exhibit deteriorative effects on both vascular structure and function, independent of hypertension.

Functional characterization of collaterals in the human gingiva by laser speckle contrast imaging

OBJECTIVE

The rate of blood flow between the various areas of the gingiva in resting position and under challenge is unknown. In this study, the LSCI method was used to map spatial and temporal changes in gingival blood flow after transient compression.

METHODS

Horizontal, vertical, and papilla base compressions were applied on the attached gingiva in 21 healthy patients (13 women, 8 men). LSCI was used to determine dynamic changes in regional blood flow during a five-second occlusion interval and subsequent reperfusion for twenty minutes.

RESULTS

Resting blood flow in the attached gingiva apical to the papillae was higher as compared to that in the midbuccal area of the teeth. During short-term horizontal compression, ischemia was greater coronal than apical to the occlusion line. Postocclusive hyperemia was observed not only in the regions affected by ischemia but encompassed a wider area. Hyperemic response was more pronounced and prolonged in male than in female patients.

CONCLUSIONS

Blood flow in the attached gingiva shows spatial differences. Our findings corroborate the apicocoronal orientation of blood circulation. Periodontal and papillary collaterals may have little role in the blood supply of the adjacent attached gingiva under physiological conditions.

Reliability of microvascular responsiveness measures derived from near-infrared spectroscopy across a variety of ischemic periods in young and older individuals

BACKGROUND

Cardiovascular disease (CVD) is associated with impairments in microvascular responsiveness. Therefore, reliably assessing microvascular function is clinically relevant. Thus, this study aimed to examine the reliability of the near-infrared spectroscopy (NIRS)-derived oxygen saturation (StO₂) reperfusion slope, a measure of microvascular responsiveness, to four different vascular occlusion tests (VOT) of different durations in young and older participants.

METHODS

Eight healthy young (29 ± 5 yr) and seven older (67 ± 4 yr) men participated in four NIRS combined with VOT (NIRS-VOT; 30 s, 1, 3, and 5 min) in the leg microvasculature on two visits separated by 1-2 weeks. Vascular responsiveness was determined by the StO₂ reperfusion slope. The coefficient of variation (CV), repeatability, reliability (ICC), and the limits of agreement (LOA) were calculated for the NIRS-derived reperfusion slopes for each occlusion duration and visit.

RESULTS

CV for the StO₂ reperfusion slope following 30 s, 1, 3 and 5 min of occlusion were 33 ± 29%, 19 ± 21%, 14 ± 12%, and 12 ± 10%, respectively. Repeatability values following 30 s, 1, 3 and 5 min occlusions were 20%, 1%, 4% and 21%, respectively. The ICC for the StO₂ reperfusion slopes for each occlusion duration were 0.29, 0.42, 0.84, and 0.88 following 30 s, 1, 3 and 5 min of occlusion, respectively. LOA values between visit 1 and 2 for occlusions were not different from zero. There were no age-related differences for all variables of the study.

CONCLUSION

NIRS-derived StO₂ reperfusion slope, has good reliability across a range of occlusion durations with the strongest reliability during longer occlusion durations.

Mechanisms of Dysfunction in the Aging Vasculature and Role in Age-Related Disease

Advancing age promotes cardiovascular disease (CVD), the leading cause of death in the United States and many developed nations. Two major age-related arterial phenotypes, large elastic artery stiffening and endothelial dysfunction, are independent predictors of future CVD diagnosis and likely are responsible for the development of CVD in older adults. Not limited to traditional CVD, these age-related changes in the vasculature also contribute to other age-related diseases that influence mammalian health span and potential life span. This review explores mechanisms that influence age-related large elastic artery stiffening and endothelial dysfunction at the tissue level via inflammation and oxidative stress and at the cellular level via Klotho and energy-sensing pathways (AMPK [AMP-activated protein kinase], SIRT [sirtuins], and mTOR [mammalian target of rapamycin]). We also discuss how long-term calorie restriction-a health span- and life span-extending intervention-can prevent many of these age-related vascular phenotypes through the prevention of deleterious alterations in these mechanisms. Lastly, we discuss emerging novel mechanisms of vascular aging, including senescence and genomic instability within cells of the vasculature. As the population of older adults steadily expands, elucidating the cellular and molecular mechanisms of vascular dysfunction with age is critical to better direct appropriate and measured strategies that use pharmacological and lifestyle interventions to reduce risk of CVD within this population.

Associations of sex, age and adiposity in endothelium-independent dilation in children

OBJECTIVE

To examine the association of age, sex, and obesity status on endothelial-independent dilation (EID) among children and adolescents.

STUDY DESIGN

This study examined 264 children (143 males) between 8 to 18 years old (mean  ±  SD: age  =  14.3  ±  2.7 years). Endothelial-independent dilation was assessed via ultrasound imaging of the brachial artery following administration of 0.3 milligrams of sublingual nitroglycerin. A one-way analysis of variance with Bonferroni post hoc comparisons assessed sex-differences in percent peak EID dilation (EID%-peak) and EID area under the curve (EID%-AUC), while analysis of covariance (ANCOVA) adjusted for race, age, body mass index percentile (BMI-percentile), and brachial artery diameter. Multiple linear regression evaluated the association of sex, age, BMI-percentile, percent body fat (%BF), and brachial artery diameter on EID.

RESULTS

Prior to adjustment, EID%-peak was significantly higher among females than males (mean  ±  SE: 26.9  ±  0.5% versus 22.9  ±  0.6%, p  <  0.001, respectively); similar findings for EID%-AUC (4214%  ±  105%·s versus 3398%  ±  97%·s, p  <  0.001) were observed. After adjusting for covariates, EID%-AUC remained consistent (p  =  0.03) while EID%-peak was not significantly different between sexes (p  =  0.21). EID%-peak was significantly higher among normal weight compared to obese participants (p  =  0.04), while no differences were observed between obesity status after adjustment for brachial artery diameter (p  =  0.64). Both unadjusted (p  =  0.16) and adjusted EID%-AUC (p  =  0.24) was not significantly different between obesity status. BMI-percentile was not associated with EID%-peak (p  =  0.76) or EID%-AUC (p  =  0.30). Additionally, %BF was not associated with EID%-peak (p  =  0.56) or EID%-AUC (p  =  0.15). After adjusting for brachial artery diameter, BMI-percentile, and age, males had lower EID%-AUC (p  =  0.03) and lower but not significant EID%-peak (p  =  0.21).

SIGNIFICANCE

Vascular smooth muscle function was significantly lower among male children and adolescents, which is suggestive that impaired EID and increased cardiovascular disease risk among males may begin in childhood. Interestingly, obesity status and BMI-percentile was not associated with EID in children and adolescents after adjusting for brachial artery diameter.

Physiological adaptation of endothelial function to pregnancy: systematic review and meta-analysis

OBJECTIVES

To establish reference values for flow-mediated dilatation (FMD) and brachial artery diameter (BAD) in pregnancy and to provide insight into the physiological and pathological course of endothelial adaptation throughout human singleton pregnancy.

METHODS

A meta-analysis was performed following a systematic review of current literature on FMD, as a derivative for endothelial function, and BAD, throughout uncomplicated and complicated pregnancy. PubMed (NCBI) and EMBASE (Ovid) electronic databases were used for the literature search, which was performed from inception to 9 June 2016. To allow judgment of changes in comparison with the non-pregnant state, studies were required to report both non-pregnant mean reference of FMD (matched control group, prepregnancy or postpartum measurement) and mean FMD at a predetermined and reported gestational age. Pooled mean differences between the reference and pregnant FMD values were calculated for predefined intervals of gestational age.

RESULTS

Fourteen studies that enrolled 1231 participants met the inclusion criteria. Publication dates ranged from 1999 to 2014. In uncomplicated pregnancy, FMD was increased in the second and third trimesters. Between 15 and 21 weeks of gestation, absolute FMD increased the most, by a mean (95% CI) of 1.89% (0.25-3.53%). This was a relative increase of 22.5% (3.0-42.0%) compared with the non-pregnant reference. BAD increased progressively, in a steady manner, by the second trimester but not significantly in the first half of the second trimester. We could not discern differences in FMD and BAD between complicated and uncomplicated pregnancies at 29-35 weeks' gestation, reported in the three studies that met our inclusion criteria. Despite the increase in FMD and BAD throughout gestation, both reference curves were characterized by wide 95% CIs.

CONCLUSION

During healthy pregnancy, endothelium-dependent vasodilatation and BAD increase. Women with a complicated pregnancy had FMD values within the lower range when compared with those with uncomplicated pregnancy but, as a group, did not differ from each other. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Coronary endothelial function is better in healthy premenopausal women than in healthy older postmenopausal women and men

BACKGROUND

Premenopausal women have fewer cardiovascular disease (CVD) events than postmenopausal women and age-matched men, but the reasons are not fully understood. Coronary endothelial function (CEF), a barometer of coronary vascular health, promises important insights into age and sex differences in atherosclerotic CVD risk, but has not been well characterized in healthy individuals because of the invasive nature of conventional CEF measurements. Recently developed magnetic resonance imaging (MRI) methods were used to quantify CEF (coronary area and flow changes in response to isometric handgrip exercise (IHE), an endothelial-dependent stressor) to test the hypothesis that healthy women have better CEF compared to men particularly at a younger age.

METHODS

The study participants were 50 healthy women and men with no history of coronary artery disease (CAD) or traditional CV risk factors and Agatston coronary calcium score (on prior CT) <10 for those ≥ 50 years. Coronary cross-sectional area (CSA) measurements and flow-velocity encoded images (CBF) were obtained at baseline and during continuous IHE using 3T breath-hold cine MRI-IHE. CEF (%change in CSA and CBF with IHE) comparisons were made according to age and sex, and all women ≥50 years were post-menopausal.

RESULTS

In the overall population, there were no differences in CEF between men and women. However, when stratified by age and sex the mean changes in CSA and CBF during IHE were higher in younger premenopausal women than older postmenopausal women (%CSA: 15.2±10.6% vs. 7.0±6.8%, p = 0.03 and %CBF: 59.0±37.0% vs. 30.5±24.5% p = 0.02). CBF change was also nearly two-fold better in premenopausal women than age-matched men (59.0±37.0% vs. 33.6±12.3%, p = 0.03).

CONCLUSIONS

Premenopausal women have nearly two-fold better mean CEF compared to postmenopausal women. CEF, measured by CBF change is also better in premenopausal women than age-matched men but there are no sex differences in CEF after menopause. Fundamental age and sex differences in CEF exist and may contribute to differences in the development and clinical manifestations of atherosclerotic CVD, and guide future trials targeting sex-specific mechanisms of atherogenesis.

Associations between endothelial dysfunction and clinical and laboratory parameters in children and adolescents with sickle cell anemia

Background

Hematological changes can drive damage of endothelial cells, which potentially lead to an early endothelial dysfunction in patients with sickle cell anemia (SCA). An association may exist between endothelial dysfunction and several clinical manifestations of SCA. The present study aims to evaluate the links between changes in endothelial function and clinical and laboratory parameters in children and adolescents with SCA.

Methods

This study included 40 children and adolescents with stable SCA as well as 25 healthy children; aged 6–18 years. All study subjects were evaluated for endothelial function using Doppler ultrasonography. In addition, a number of laboratory assays were performed, including reticulocyte and leukocyte counts as well as measurement of circulating levels of total bilirubin, C-reactive protein (CRP), glucose, lipoproteins and peripheral oxyhemoglobin saturation. These parameters were also compared between SCA patients who were undertaking hydroxyurea (HU) and those who were not.

Results

Flow-mediated vasodilation (FMD) values were found to be reduced in SCA patients compared with those detected in healthy controls. SCA individuals with lower FMD values exhibited higher number of hospital admissions due to vaso-occlusive events. Additional analyses revealed that patients who had decreased FMD values exhibited higher odds of acute chest syndrome (ACS) episodes. A preliminary analysis with limited number of individuals failed to demonstrate significant differences in FMD values between SCA individuals who were treated with HU and those who were not.

Conclusions

Children and adolescents with SCA exhibit impaired endothelial function. Reductions in FMD values are associated with ACS. These findings underline the potential use of FMD as screening strategy of SCA patients with severe prognosis at early stages.

Children and Adolescents Macrovascular Reactivity Level and Dynamics, But Not the Microvascular Response, is Associated with Body Mass Index and Arterial Stiffness Levels

INTRODUCTION

The existing evidence indicates that primary prevention of atherosclerotic disease should begin in childhood. Detection of children and adolescents at risk for atherosclerosis may allow early intervention to decrease the atherosclerotic process, thereby preventing or delaying cardiovascular disease. Vascular reactivity (VR) is altered even by early atherosclerosis. Obesity is a main cardiovascular risk factor (CVRF) observed in childhood. If childhood obesity associates impaired macro and/or micro VR is controversial.

AIMS

To characterize macro and micro VR analyzing the stimulus and vascular response temporal profiles in children and adolescents considering their body mass index (BMI); and to assess potential associations between subjects' characteristics and the hyperemic stimulus and/or VR.

METHODS

Healthy subjects (n = 99, age 5-17 years, female 46%) were included. Considering the BMI, normal, overweight and obese groups were defined. CVRF exposure was assessed. Brachial flow-mediated dilation and reactive hyperemia, associated with transient ischemia (forearm cuff-inflation) were evaluated. Diameter, flow velocities, resistive indexes and shear-stress were determined before, during and after cuff-release. Complimentary VR indexes were computed. Aortic stiffness and aortic and brachial blood pressure were determined.

RESULTS

Obese showed the lowest and slowest macrovascular response (p < 0.05). Micro VR was not associated with obesity. Higher aortic stiffness levels were associated with slower macrovascular responses (p < 0.05).

CONCLUSION

Childhood obesity associates not only reduced, but also slowed macrovascular reactivity. Microvascular response to transient ischemia is preserved in obese children. Macro and microvascular responses would be non-associated phenomena in childhood. During childhood, VR dynamics would depend on the arterial stiffness.

Exposure-response modeling of flow-mediated dilation provides an unbiased and informative measure of endothelial function

The brachial artery flow-mediated dilation (FMD) test is the most widely utilized method to evaluate endothelial function noninvasively in humans by calculating the percent change in diameter (FMD%). However, the underutilized velocity and diameter time course data, coupled with confounding influences in shear exposure, noise, and upward bias, make the FMD test less desirable. In this study, we developed an exposure-response, model-based approach that not only quantifies FMD based on the rich velocity and diameter data, it overcomes previously acknowledged challenges. FMD data were obtained from 15 apparently healthy participants, each exposed to four different cuff occlusion durations. The velocity response following cuff release was described by an exponential model with two parameters defining peak velocity and rate of decay. Shear exposure derived from velocity was used to drive the diameter response model, which consists of additive constriction and dilation terms. Three parameters describing distinct aspects of the vascular response to shear (magnitude of the initial constriction response, and magnitude and time constant of the dilation response) were estimated for both the individuals and population. These parameters are independent of shear exposure. Thus this approach produces identifiable and physiologically meaningful parameters that may provide additional information for comparing differences between experimental groups or over time, and provides a means to completely account for shear exposure.NEW & NOTEWORTHY While flow-mediated dilation (FMD) is a valuable tool for evaluating endothelial function, analytical challenges include confounding influences of shear exposure, upward bias, and underutilization of rich time course data collected during FMD testing. We have developed an exposure-response, model-based approach that quantifies endothelial function based on the velocity and diameter data and fully accounts for shear exposure. It produces physiologically meaningful parameters that may provide useful information for comparing differences between experimental groups or over time.

YKL-40 Level and Hypertension Incidence: A Population-Based Nested Case-Control Study in China

Background

Human cartilage glycoprotein‐39 (YKL‐40) has been suggested to be a new marker of inflammation, atherosclerosis, and endothelial dysfunction. However, whether a higher level of YKL‐40 is an independent risk factor for hypertension incidence is still unknown.

Methods and Results

In a nested case‐control study within a prospective cohort of 12 423 initially healthy Chinese adults, we measured baseline plasma concentrations of YKL‐40 among 700 new‐onset hypertension cases and 700 age‐ and sex‐matched controls. Multiple conditional logistic regression analyses were used to calculate the odds ratios (95% CIs) of hypertension associated with higher levels of YKL‐40 both in the total population and in the age‐ (>55 and ≤55 years) and sex‐matched subgroups. Among the total population, YKL‐40 levels were not associated with hypertension risk. In the subgroup older than 55 years, odds ratios (95% CIs) of hypertension for those in the two higher tertiles of YKL‐40 were 1.23 (0.77–1.97) and 1.59 (0.99–2.55) (P for linear trend=0.05). In the male subgroup, odds ratios (95% CIs) of hypertension for those in the two higher tertiles of YKL‐40 were 1.55 (0.88–2.72) and 2.09 (1.14–3.82) (P for linear trend=0.02). An interaction effect was observed between YKL‐40 and sex (P for interaction <0.01) but not between YKL‐40 and age (P for interaction=0.21). High YKL‐40 level significantly increased hypertension risk in men but decreased hypertension risk with a trend although not significant in women.

Conclusions

This study suggests that YKL‐40 is associated with hypertension incidence only among men. The study findings need to be further verified by prospective cohort studies or clinical trials.

Reactivity to low-flow as a potential determinant for brachial artery flow-mediated vasodilatation

Previous studies have reported a vasoconstrictor response in the radial artery during a cuff-induced low-flow condition, but a similar low-flow condition in the brachial artery results in nonuniform reactivity. This variable reactivity to low-flow influences the subsequent flow-mediated dilatation (FMD) response following cuff-release. However, it is uncertain whether reactivity to low-flow is important in data interpretation in clinical populations and older adults. This study aimed to determine the influence of reactivity to low-flow on the magnitude of brachial artery FMD response in middle-aged and older individuals with diverse cardiovascular risk profiles. Data were analyzed from 165 individuals, divided into increased cardiovascular risk (CVR: n = 115, 85M, 67.0 ± 8.8 years) and healthy control (CTRL: n = 50, 30M, 63.2 ± 7.2 years) groups. Brachial artery diameter and blood velocity data obtained from Doppler ultrasound were used to calculate FMD, reactivity to low-flow and estimated shear rate (SR) using semiautomated edge-detection software. There was a significant association between reactivity to low-flow and FMD in overall (r = 0.261), CTRL (r = 0.410) and CVR (r = 0.189, all P < 0.05) groups. Multivariate regression analysis found that reactivity to low-flow, peak SR, and baseline diameter independently contributed to FMD along with sex, the presence of diabetes, and smoking (total R(2) = 0.450). There was a significant association between reactivity to low-flow and the subsequent FMD response in the overall dataset, and reactivity to low-flow independently contributed to FMD These findings suggest that reactivity to low-flow plays a key role in the subsequent brachial artery FMD response and is important in the interpretation of FMD data.

Repeatability of vascular responsiveness measures derived from near-infrared spectroscopy

Near‐infrared spectroscopy (NIRS)‐derived measures of tissue oxygen saturation (StO₂) have been recently shown to significantly correlate with the widely used method for noninvasively assessing vascular endothelial function, flow‐mediated dilation (FMD). The purpose of this study was to examine the intraday and interday reliability of the reperfusion slope of StO₂ (slope 2 StO₂) and compare it to FMD. Ultrasound‐derived FMD was quantified following 5 min of distal cuff occlusion of the popliteal artery in nine healthy young men (26 ± 3 years). An FMD test was performed each of 4 days, with a fifth involving three tests. FMD was calculated as the greatest percent change in diameter from baseline (%FMD). StO₂ was measured using NIRS throughout each test, with slope 2 StO₂ being calculated as the upslope of 10‐sec following cuff release. Reliability was determined using repeatability, intraclass correlation coefficients (ICC), and coefficient of variation (CV). Repeatability of slope 2 StO₂ was better than %FMD for both intraday (0.43 and 5.65, respectively) and interday (0.48 and 4.82, respectively) comparisons; approximately 30% of mean values for slope 2 StO₂ could be attributed to measurement error, whereas 100% of mean FMD could be for both intraday and interday comparisons. Similarly, ICC and CV values indicated stronger reliability of slope 2 StO₂ compared to %FMD for both intraday (ICC 0.92 and 0.36, respectively; CV 9 ± 4% and 44 ± 24%, respectively) and interday (ICC 0.94 and 0.25, respectively; CV 14 ± 5% and 40 ± 22%, respectively) comparisons. In conclusion, NIRS‐derived slope 2 StO₂ can be used as a reliable measure of vascular reactivity.

Oral L-arginine improves endothelial function in healthy individuals older than 70 years

Ageing is associated with progressive endothelial dysfunction in normal humans. Flow-mediated dilation (FMD) of the brachial artery is impaired in elderly individuals with cardiovascular disease and vascular nitric oxide (NO) bioavailability is reduced. We investigated whether oral L-arginine, the substrate for NO synthesis, can improve impaired FMD in healthy very old people. In a prospective, double-blind, randomized crossover trial, 12 healthy old subjects (age 73.8 6 2.7 years) took L-arginine (8 g p.o. two times daily) or placebo for 14 days each, separated by a wash-out period of 14 days. FMD was determined by high-resolution ultrasound in the brachial artery during reactive hyperaemia. Baseline artery diameter was 3.88 6 0.18 mm. l-Arginine signifi cantly improved FMD (to 5.7 6 1.2%, p, 0.0001), whereas placebo had no effect (-0.25 6 0.7%; n.s.). After L-arginine, plasma levels of L-arginine increased signifi cantly (114.9 6 11.6 versus 57.4 6 5.0 mmol/l), but placebo had no effect. As NO synthesis can be antagonized by its endogenous inhibitor asymmetric dimethyl L-arginine (ADMA), we determined ADMA plasma concentrations, which were elevated at baseline in comparison to healthy middle-aged individuals (3.9 6 0.2 versus 1.0 6 0.1 mmol/l; p, 0.0001). ADMA remained unchanged during treatment, but L-arginine supplementation normalized the L-arginine/ADMA ratio (p, 0.05). We conclude that in healthy very old age endothelial function is impaired and may be improved by oral L-arginine supplementation, probably due to normalization of the L-arginine/ADMA ratio.

Vascular Function at Baseline in the Hemodialysis Fistula Maturation Study

Background

End‐stage renal disease is accompanied by functional and structural vascular abnormalities. The objective of this study was to characterize vascular function in a large cohort of patients with end‐stage renal disease, using noninvasive physiological measurements, and to correlate function with demographic and clinical factors.

Methods and Results

We analyzed cross‐sectional baseline data from the Hemodialysis Fistula Maturation Study, a multicenter prospective observational cohort study of 602 patients with end‐stage renal disease from 7 centers. Brachial artery flow‐ and nitroglycerin‐mediated dilation, carotid‐femoral and ‐radial pulse wave velocity, and venous occlusion plethysmography were performed prior to arteriovenous fistula creation. Relationships of these vascular function measures with demographic, clinical, and laboratory factors were evaluated using linear mixed‐effects models. Arterial function, as assessed by flow‐ and nitroglycerin‐mediated dilation and carotid‐femoral pulse wave velocity, worsened with increasing age and diabetes mellitus. Venous capacitance decreased with diabetes mellitus but not with age. Flow‐mediated dilation was higher among patients undergoing maintenance dialysis than for those at predialysis, and a U‐shaped relationship between serum phosphorus concentration and flow‐mediated dilation was evident. Partial correlations among different measures of vascular function, adjusting for demographic factors, diabetes mellitus, and clinical center, were modest or essentially nonexistent.

Conclusions

Multiple demographic and clinical factors were associated with the functions of vessels of different sizes and types in this large cohort of patients with end‐stage renal disease. Low correlations between the different measures, controlling for demographic factors, diabetes mellitus, and center, indicated that these different types of vascular function otherwise vary heterogeneously across patients.

A single Mediterranean meal does not impair postprandial flow-mediated dilatation in healthy men with subclinical metabolic dysregulations

Cardiovascular risk factors are known to exacerbate high-saturated fatty acid meal (HSFAM)-induced endothelial dysfunction, but the influence of subclinical metabolic dysregulations and the acute impact of a single mixed Mediterranean-type meal (MMM) remains unknown. Thus, this study has the objective to evaluate the metabolic and vascular effect of such meals in healthy subjects with or without subclinical fasting metabolic dysregulations. Twenty-eight healthy males without overt cardiovascular risk factors randomly ingested 1 of 2 isocaloric meals on separate days. Plasma metabolic markers, fatty acid (FA) profile, and endothelial function (flow-mediated dilatation; FMD) were assessed at baseline and 2 and 4 h after meal ingestion. Unsupervised hierarchical clustering identified 2 subgroups of participants (n = 11 and 17) differing by their baseline metabolic profiles. The MMM did not significantly alter postprandial endothelial function in all subjects, irrespective of baseline metabolic parameters. In contrast, the HSFAM induced postprandial endothelial dysfunction (Δ%FMDabsolute = -5.28 ± 2.54, p < 0.01 vs. MMM) in a subgroup of individuals with significantly greater body mass index, fasting insulinemia, and lipid parameters (n = 11). Finally, the postprandial plasma FA profiles were differentially enriched by the HSFAM and MMM, notably with saturated FAs and omega-3 polyunsaturated FAs, respectively. Collectively, our results highlight the detrimental impact of a single HSFAM on endothelial function in healthy individuals displaying subclinical fasting metabolic dysregulations. Such individuals could benefit from MMM, demonstrated herein to be without any acute detriment to endothelial function.

Adherence to guidelines strongly improves reproducibility of brachial artery flow-mediated dilation

BACKGROUND

Brachial artery FMD is widely used as a non-invasive measure of endothelial function. Adherence to expert guidelines is believed to be of vital importance to obtain reproducible measurements. We conducted a systematic review of studies reporting on the reproducibility of the FMD in order to determine the relation between adherence to current expert guidelines for FMD measurement and its reproducibility.

METHODS

Medline-database was searched through July 2015 and 458 records were screened for FMD reproducibility studies reporting the mean difference and variance of repeated FMD measurements. An adherence score was assigned to each of the included studies based on reported adherence to published guidelines on the assessment of brachial artery FMD. A Typical Error Estimate (TEE) of the FMD was calculated for each included study. The relation between the FMD TEE and the adherence score was investigated by means of Pearson correlation coefficients and multiple linear regression analysis.

RESULTS

Twenty-seven studies involving 48 study groups and 1537 subjects were included in the analyses. The adherence score ranged from 2.4 to 9.2 (out of a maximum of 10) and was strongly and inversely correlated with FMD TEE (adjusted R(2) = 0.36, P < 0.01). Use of automated edge-detection software, continuous diameter measurement, true peak diameter for %FMD calculation, a stereostatic probe holder, and higher age emerged as factors associated with a lower FMD TEE.

CONCLUSIONS

These data demonstrate that adherence to current expert consensus guidelines and applying contemporary techniques for measuring brachial artery FMD decreases its measurement error.

Varying patterns of brachial artery flow-mediated dilatation in women with polycystic ovary syndrome and controls: An application of the group-based trajectory modeling

PURPOSE

To identify changing patterns of absolute change in brachial artery lumen diameter (LD) after reactive hyperemia in women with polycystic ovary syndrome (PCOS) and controls and to quantify the association of PCOS status and participants' factors with these patterns.

METHODS

Brachial flow-mediated dilation was measured in 128 women with PCOS and 148 controls aged 30-60 years. Group-based trajectory modeling was used to investigate absolute change in LD every 30 seconds for 2 minutes after occluding cuff deflation. Multinomial logistic regression was used to identify factors associated with trajectories.

RESULTS

Three patterns emerged, namely nondilators (42.2%), dilators (44.6%), and enhanced dilators (13.0%). The proportion of women with PCOS did not differ across groups. Independently of age and PCOS status, larger baseline LD (odds ratio; 95% confidence interval: 2.51; 1.29, 4.89) and lower insulin levels (0.70; 0.52, 0.93) were associated with nondilators rather than with dilators. Higher total cholesterol was associated with dilators in women with PCOS but with nondilators in controls.

CONCLUSIONS

Trajectory modeling identified distinct patterns of change in LD and factors associated with the endothelial response. This method may be a useful tool to understand the brachial flow-mediated vasodilator response.

Assessments of endothelial function and arterial stiffness are reproducible in patients with COPD

Background

Elevated cardiovascular disease risk is observed in patients with COPD. Non-invasive assessments of endothelial dysfunction and arterial stiffness have recently emerged to provide mechanistic insight into cardiovascular disease risk in COPD; however, the reproducibility of endothelial function and arterial stiffness has yet to be investigated in this patient population.

Objectives

This study sought to examine the within-day and between-day reproducibility of endothelial function and arterial stiffness in patients with COPD.

Methods

Baseline diameter, peak diameter, flow-mediated dilation, augmentation index, augmentation index at 75 beats per minute, and pulse wave velocity were assessed three times in 17 patients with COPD (six males, eleven females, age range 47–75 years old; forced expiratory volume in 1 second =51.5% predicted). Session A and B were separated by 3 hours (within-day), whereas session C was conducted at least 7 days following session B (between-day). Reproducibility was assessed by: 1) paired t-tests, 2) coefficients of variation, 3) coefficients of variation prime, 4) intra-class correlation coefficient, 5) Pearson’s correlations (r), and 6) Bland–Altman plots. Five acceptable assessments were required to confirm reproducibility.

Results

Six out of six within-day criteria were met for endothelial function and arterial stiffness outcomes. Six out of six between-day criteria were met for baseline and peak diameter, augmentation index and pulse wave velocity, whereas five out of six criteria were met for flow-mediated dilation.

Conclusion

The present study provides evidence for within-day and between-day reproducibility of endothelial function and arterial stiffness in patients with COPD.

Fibrosis-related biomarkers and large and small vessel disease: the Cardiovascular Health Study

OBJECTIVE

Fibrosis has been implicated in a number of pathological, organ-based conditions of the liver, kidney, heart, and lungs. The objective of this study was to determine whether biomarkers of fibrosis are associated with vascular disease in the large and/or small vessels.

METHODS

We evaluated the associations of two circulating biomarkers of fibrosis, transforming growth factor-β (TGF-β) and procollagen type III N-terminal propeptide (PIIINP), with incident peripheral artery disease (PAD) and subclinical macrovascular (carotid intima-media thickness, flow-mediated vasodilation, ankle-brachial index, retinal vein diameter), and microvascular (retinal artery diameter and retinopathy) disease among older adults in the Cardiovascular Health Study. We measured TGF-β and PIIINP from samples collected in 1996 and ascertained clinical PAD through 2011. Measurements of large and small vessels were collected between 1996 and 1998.

RESULTS

After adjustment for sociodemographic, clinical, and biochemical risk factors, TGF-β was associated with incident PAD (hazard ratio [HR] = 1.36 per doubling of TGF-β, 95% confidence interval [CI] = 1.04, 1.78) and retinal venular diameter (1.63 μm per doubling of TGF-β, CI = 0.23, 3.02). PIIINP was not associated with incident PAD, but was associated with carotid intima-media thickness (0.102 mm per doubling of PIIINP, CI = 0.029, 0.174) and impaired brachial artery reactivity (-0.20% change per doubling of PIIINP, CI = -0.39, -0.02). Neither TGF-β nor PIIINP were associated with retinal arteriolar diameter or retinopathy.

CONCLUSIONS

Serum concentrations of fibrosis-related biomarkers were associated with several measures of large vessel disease, including incident PAD, but not with small vessel disease. Fibrosis may contribute to large vessel atherosclerosis in older adults.

Flow-mediated dilation is associated with cardiovascular events in non-valvular atrial fibrillation patients

BACKGROUND

Atrial fibrillation is associated with multiple atherosclerotic risk factors and predisposes to cardiovascular events (CVE). Endothelial dysfunction is associated with atherosclerosis and independently predicts CVE. The aim of the study was to evaluate the association between endothelial dysfunction, as assessed by flow-mediated dilation (FMD), and CVE in AF patients.

METHODS

We prospectively measured FMD in 514 non-valvular AF patients on anticoagulant treatment with vitamin K antagonists. Patients were followed-up for a mean time of 23.5 months. The main composite outcome of the study was the occurrence of stroke/TIA, myocardial infarction, urgent revascularization and cardiovascular death.

RESULTS

Median value of FMD was 4.6% [IQR 1.46-8.00]. A CVE occurred in 44 patients (8.56%):non-fatal myocardial infarction (MI) in 7, fatal MI in 2, stent/coronary artery by-pass graft (CABG) in 10, ischemic non-fatal stroke in 10, fatal stroke in 3, transient ischemic attack (TIA) in 1, and cardiovascular death in 11 patients. Patients who experienced a CVE showed significantly reduced FMD compared to those who did not (3.06% [IQR 0.00-6.00] vs 4.67% [IQR 1.58-8.22], p=0.027). During a mean follow-up of 23.5 months, the rate of CVE was significantly higher in subjects with FMD below median (<4.6%) than in those with FMD above median (27 vs 17, log-rank test p=0.006). COX analysis demonstrated that low FMD (below median) (HR: 2.20, CI 95%:1.13-4.28, p=0.020), age (HR: 1.08, CI 95%: 1.03-1.12, p<0.001), smoking (HR: 4.15, CI 95%: 1.63-10.6, p=0.003) and history of stroke/TIA (HR: 2.38, CI 95%: 1.13-5.04, p=0.023) independently predicted CVE.

CONCLUSIONS

In AF patients low FMD is associated with increased risk of CVE suggesting that impaired artery dilatation predisposes to atherosclerotic complications.

Potentially spurious correlations between arterial size, flow-mediated dilation, and shear rate

The use of indices formed from the ratio of 2 variables often generates spurious correlations with other variables that are mathematically coupled. In this context, we examined the correlations between percent flow-mediated dilation, baseline diameter, and shear rate. In a sample of 315 participants, with and without substantial vascular risk factors, the observed correlation coefficients between the variables were of a similar magnitude to those reported in the literature. We then applied a Monte Carlo procedure based on random permutations to remove any physical or physiological explanation for these correlations. We found that the median residual correlation coefficients were comparable with those observed in our original sample. When the confounding influence of artery size was adjusted for, the mean difference in percent flow-mediated dilation between high-risk and low-risk samples was halved. These findings indicate that the widely reported correlations between flow-mediated dilation, basal artery diameter, and shear rate have a substantial spurious component. This is because percent flow-mediated dilation and shear rate are mathematically coupled to artery size.

Vegan diet, subnormal vitamin B-12 status and cardiovascular health

Vegetarian diets have been associated with atherosclerosis protection, with healthier atherosclerosis risk profiles, as well as lower prevalence of, and mortality from, ischemic heart disease and stroke. However, there are few data concerning the possible cardiovascular effects of a vegan diet (with no meat, dairy or egg products). Vitamin B-12 deficiency is highly prevalent in vegetarians; this can be partially alleviated by taking dairy/egg products in lact-ovo-vegetarians. However, metabolic vitamin B-12 deficiency is highly prevalent in vegetarians in Australia, Germany, Italy and Austria, and in vegans (80%) in Hong Kong and India, where vegans rarely take vitamin B-12 fortified food or vitamin B-12 supplements. Similar deficiencies exist in northern Chinese rural communities consuming inadequate meat, egg or dairy products due to poverty or dietary habits. Vascular studies have demonstrated impaired arterial endothelial function and increased carotid intima-media thickness as atherosclerosis surrogates in such metabolic vitamin B-12 deficient populations, but not in lactovegetarians in China. Vitamin B-12 supplementation has a favourable impact on these vascular surrogates in Hong Kong vegans and in underprivileged communities in northern rural China. Regular monitoring of vitamin B-12 status is thus potentially beneficial for early detection and treatment of metabolic vitamin B-12 deficiency in vegans, and possibly for prevention of atherosclerosis-related diseases.

Combination of ¹²³I-metaiodobenzylguanidine scintigraphy and flow-mediated dilation for the detection of patients with coronary spastic angina

BACKGROUND

This study evaluated the usefulness of cardiac sympathetic nerve activity, estimated by (123)I-MIBG scintigraphy, and endothelial function, estimated by flow-mediated dilation (FMD), in the detection of coronary spastic angina (CSA).

METHODS AND RESULTS

We compared 78 consecutive patients suspected of CSA with ten age-matched controls. On the basis of a spasm provocation test with acetylcholine, 53 patients were diagnosed as CSA and 25 patients were considered to have chest-pain syndrome (CPS). The total defect score (TDS) by delayed (123)I-MIBG scintigraphy was significantly higher in both patient groups than in controls (P < 0.05), and was significantly higher in CSA than in CPS patients (P = 0.02). The heart/mediastinum activity (H/M) ratio by delayed (123)I-MIBG scintigraphy and FMD were significantly lower in both patient groups than in controls (P < 0.05), and were lower in CSA than in CPS patients (P = 0.04). In receiver-operating curve analysis, the areas under the curve for TDS, H/M, and FMD were 0.78, 0.72, and 0.70, respectively. The combination of delayed (123)I-MIBG scintigraphy and FMD showed a higher diagnostic value than either method alone.

CONCLUSIONS

(123)I-MIBG scintigraphy and FMD can distinguish CSA patients among patients complaining of chest pain at rest, with good sensitivity and specificity.

The effect of exercise intensity on endothelial function in physically inactive lean and obese adults

Purpose

To examine the effects of exercise intensity on acute changes in endothelial function in lean and obese adults.

Methods

Sixteen lean (BMI <25, age 23±3 yr) and 10 obese (BMI >30, age 26±6 yr) physically inactive adults were studied during 3 randomized admissions [control (C, no exercise), moderate-intensity exercise (M, @ lactate threshold (LT)) and high-intensity exercise (H, midway between LT and VO₂peak) (30 min)]. Endothelial function was assessed by flow-mediated dilation (FMD) at baseline and 1, 2, and 4 h post-exercise.

Results

RM ANCOVA revealed significant main effects for group, time, and group x condition interaction (p<0.05). A diurnal increase in FMD was observed in lean but not obese subjects. Lean subjects exhibited greater increases in FMD than obese subjects (p = 0.0005). In the obese group a trend was observed for increases in FMD at 2- and 4-hr after M (p = 0.08). For lean subjects, FMD was significantly elevated at all time points after H. The increase in FMD after H in lean subjects (3.2±0.5%) was greater than after both C (1.7±0.4%, p = 0.015) and M (1.4±0.4%, p = 0.002). FMD responses of lean and obese subjects significantly differed after C and H, but not after M.

Conclusion

In lean young adults, high-intensity exercise acutely enhances endothelial function, while moderate-intensity exercise has no significant effect above that seen in the absence of exercise. The FMD response of obese adults is blunted compared to lean adults. Diurnal variation should be considered when examining the effects of acute exercise on FMD.

The percentage flow-mediated dilation index: a large-sample investigation of its appropriateness, potential for bias and causal nexus in vascular medicine

The percentage flow-mediated dilation index (FMD%) scales the increase in arterial diameter (Ddiff) as a constant proportion of baseline artery diameter (Dbase). We have demonstrated, albeit with small samples, that the scaling properties of FMD% can lead to biased inferences on endothelial dysfunction. Therefore, we aimed to investigate the underlying rationale and potential bias of FMD% using a selection of new examples from the large (n = 3499) and diverse Multi-Ethnic Study of Atherosclerosis (MESA). In this dataset, we found that smaller values of Ddiff are associated with larger values of Dbase, which contradicts the scaling properties of FMD%. Consequently, FMD% 'over-scales' and naturally generates an even stronger negative correlation between itself and Dbase. Using a data simulation, we show that this FMD%-Dbase correlation can be a statistical artefact due to inappropriate scaling. The new examples we present from MESA indicate that FMD% biases the differences in flow-mediated response between men and women, Framingham risk score categories, and diseased and healthy people. We demonstrate how FMD%, as an exposure for predicting cardiovascular disease, is confounded by its dependency on Dbase, which itself could be clinically important. This critical review, incorporating an allometric analysis of a large dataset, suggests that the FMD% index has a less-than-clear rationale, can itself generate the Dbase-dependency problem, provides biased estimates of differences in the flow-mediated response, complicates the interpretation of the flow-mediated protocol and clouds the causal pathway to vascular disease. These interpretative problems can be resolved by applying accepted allometric principles to the flow-mediated response.

Relationship between flow-mediated vasodilation and cardiovascular risk factors in a large community-based study

Objective

To determine the relationships between flow-mediated vasodilation (FMD) and cardiovascular risk factors, and to evaluate confounding factors for measurement of FMD in a large general population in Japan.

Methods

This was a cross-sectional study. A total of 5314 Japanese adults recruited from people who underwent health screening from 1 April 2010 to 31 August 2012 at 3 general hospitals in Japan. Patients’ risk factors (age, Body Mass Index, blood pressure, cholesterol parameters, glucose level and HbA1c level) and prevalence of cardiovascular disease (coronary heart disease and cerebrovascular disease) were investigated.

Results

Univariate regression analysis revealed that FMD correlated with age (r=−0.27, p<0.001), Body Mass Index (r=−0.14, p<0.001), systolic blood pressure (r=−0.18, p<0.001), diastolic blood pressure (r=−0.13, p<0.001), total cholesterol (r=−0.07, p<0.001), triglycerides (r=−0.10, p<0.001), high-density lipoprotein cholesterol (r=0.06, p<0.001), low-density lipoprotein cholesterol (r=−0.04, p=0.01), glucose level (r=−0.14, p<0.001), HbA1c (r=−0.14, p<0.001), and baseline brachial artery diameter (r=−0.43, p<0.001) as well as Framingham Risk score (r=−0.29, p<0.001). Multivariate analysis revealed that age (t value=−9.17, p<0.001), sex (t value=9.29, p<0.001), Body Mass Index (t value=4.27, p<0.001), systolic blood pressure (t value=−2.86, p=0.004), diabetes mellitus (t value=−4.19, p<0.001), smoking (t value=−2.56, p=0.01), and baseline brachial artery diameter (t value=−29.4, p<0.001) were independent predictors of FMD.

Conclusions

FMD may be a marker of the grade of atherosclerosis and may be used as a surrogate marker of cardiovascular outcomes. Age, sex, Body Mass Index, systolic blood pressure, diabetes mellitus, smoking and, particularly, baseline brachial artery diameter are potential confounding factors in the measurement of FMD.

Diabetic retinopathy and endothelial dysfunction in patients with type 2 diabetes mellitus

BACKGROUND

We investigated the relationship between endothelial dysfunction and diabetic retinopathy (DR) in patients with type 2 diabetes.

METHODS

We used a cross-sectional design to examine 167 patients with type 2 diabetes mellitus. All patients underwent biochemical and ophthalmological examination. We assessed endothelial dysfunction by a flow-mediated vasodilation method of the brachial artery. Changes in vasodilation (flow-mediated vasodilatation, %FMD) were expressed as percent change over baseline values.

RESULTS

The mean±standard deviation of patient age was 54.1±8.6 years. The %FMD was significantly lower in patients with DR than without DR. The prevalence of retinopathy decreased across increasing tertiles of %FMD. After adjusting for patients' age, sex, diabetes duration, use of insulin, use of antihypertensive, antiplatelet, and lipid lowering medications, systolic blood pressure, fasting plasma glucose, 2-hour plasma glucose, glycated hemoglobin, and urinary albumin excretion, participants with a reduced %FMD were more likely to have DR (odds ratio, 11.819; 95% confidence interval, 2.201 to 63.461; P=0.004, comparing the lowest and highest tertiles of %FMD).

CONCLUSION

Endothelial dysfunction was associated with DR, which was most apparent when the endothelial dysfunction was severe. Our study provides insights into the possible mechanism of the influence of endothelial dysfunction on the development of DR.

Flow-mediated dilation and exercise blood pressure in healthy adolescents

OBJECTIVES

Exercise blood pressure is a robust predictor of cardiovascular disease risk. Endothelial dysfunction occurs early in development of cardiovascular disease and is associated with greater exercise blood pressure in adults. However, it is not yet clear whether endothelial function is associated with exercise blood pressure in youth. The purpose of this study was to examine the relationship between endothelial function, indexed by brachial artery flow-mediated dilation, and submaximal exercise blood pressure in healthy adolescents.

DESIGN

Cross-sectional study.

METHODS

Adolescents (N=45) completed a graded submaximal treadmill test. Blood pressure was measured during rest and each exercise stage. Ultrasound measurement of brachial artery flow-mediated dilation was completed on a separate visit. Pearson correlations and multiple regression were used to assess the unadjusted and multivariate adjusted associations between flow-mediated dilation and exercise blood pressure, respectively.

RESULTS

Lower flow-mediated dilation was associated with lower diastolic blood pressure (r=0.37, p=0.01) and greater pulse pressure (r=-0.38, p=0.01) during exercise. The significance did not change when adjusting for age, gender, fitness, or resting blood pressure. Exploratory analyses suggest that flow-mediated dilation was associated with exercise diastolic blood pressure primarily among adolescents with low resting diastolic blood pressure.

CONCLUSIONS

Studies in youth are important to understand the early pathogenesis of cardiovascular disease. Findings from this study suggest that endothelial function may play a role in regulating blood pressure responses during submaximal exercise in healthy adolescents.