Assessment of vascular function: flow-mediated constriction complements the information of flow-mediated dilatation

Endothelial Function in Pulmonary Arterial Hypertension: From Bench to Bedside

Pulmonary arterial hypertension is a complex pathology whose etiology is still not completely well clarified. The pathogenesis of pulmonary arterial hypertension involves different molecular mechanisms, with endothelial dysfunction playing a central role in disease progression. Both individual genetic predispositions and environmental factors seem to contribute to its onset. To further understand the complex relationship between endothelial and pulmonary hypertension and try to contribute to the development of future therapies, we report a comprehensive and updated review on endothelial function in pulmonary arterial hypertension.

Mechanistic, participant, and movement-related factors that contribute to low-flow-mediated constriction

Endothelial function is commonly determined via the ultrasound-based flow-mediated dilation (FMD) technique which assesses arterial dilation in response to a hyperemia response following distal cuff occlusion. However, the low-flow-mediated constriction (L-FMC) response during cuff-induced ischemia is often overlooked. L-FMC provides unique information regarding endothelial function, but vascular researchers may be unclear on what this metric adds. Therefore, the objective of this review was to examine the mechanistic determinants and participant-level factors of L-FMC. Existing mechanistic studies have demonstrated that vasoreactivity to low flow may be mediated via non-nitric oxide vasodilators (i.e., endothelial hyperpolarizing factors and/or prostaglandins), inflammatory markers, and enhancement of vasoconstriction via endothelin-1. In general, participant-level factors such as aging and presence of cardiovascular conditions generally are associated with attenuated L-FMC responses. However, the influence of sex on L-FMC is unclear with divergent results between L-FMC in upper versus lower limb vessels. The ability of aerobic exercise to augment L-FMC (i.e., make more negative) is well supported, but there is a major gap in the literature concerning the mechanistic underpinnings of this observation. This review summarizes that while larger L-FMC responses are generally healthy, the impact of interventions to augment/attenuate L-FMC has not included mechanistic measures that would provide insight into non-nitric oxide-based endothelial function. Clarifications to terminology and areas of further inquiry as it relates to the specific pharmacological, individual-level factors, and lifestyle behaviors that impact L-FMC are highlighted. A greater integration of mechanistic work alongside applied lifestyle interventions is required to better understand endothelial cell function to reductions in local blood flow.

The Ultrasound Window Into Vascular Ageing: A Technology Review by the VascAgeNet COST Action

Non-invasive ultrasound (US) imaging enables the assessment of the properties of superficial blood vessels. Various modes can be used for vascular characteristics analysis, ranging from radiofrequency (RF) data, Doppler- and standard B/M-mode imaging, to more recent ultra-high frequency and ultrafast techniques. The aim of the present work was to provide an overview of the current state-of-the-art non-invasive US technologies and corresponding vascular ageing characteristics from a technological perspective. Following an introduction about the basic concepts of the US technique, the characteristics considered in this review are clustered into: 1) vessel wall structure; 2) dynamic elastic properties, and 3) reactive vessel properties. The overview shows that ultrasound is a versatile, non-invasive, and safe imaging technique that can be adopted for obtaining information about function, structure, and reactivity in superficial arteries. The most suitable setting for a specific application must be selected according to spatial and temporal resolution requirements. The usefulness of standardization in the validation process and performance metric adoption emerges. Computer-based techniques should always be preferred to manual measures, as long as the algorithms and learning procedures are transparent and well described, and the performance leads to better results. Identification of a minimal clinically important difference is a crucial point for drawing conclusions regarding robustness of the techniques and for the translation into practice of any biomarker.

Effects of androgen excess and body mass index on endothelial function in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with endothelial dysfunction; whether this is attributable to comorbid hyperandrogenism and/or obesity remains to be established. Therefore, we 1) compared endothelial function between lean and overweight/obese (OW/OB) women with and without androgen excess (AE)-PCOS and 2) examined androgens as potential modulators of endothelial function in these women. The flow-mediated dilation (FMD) test was applied in 14 women with AE-PCOS (lean: n = 7; OW/OB: n = 7) and 14 controls (CTRL; lean: n = 7, OW/OB: n = 7) at baseline (BSL) and following 7 days of ethinyl estradiol supplementation (EE; 30 µg/day) to assess the effect of a vasodilatory therapeutic on endothelial function; at each time point we assessed peak increases in diameter during reactive hyperemia (%FMD), shear rate, and low flow-mediated constriction (%LFMC). BSL %FMD was attenuated in lean AE-PCOS versus both lean CTRL (5.2 ± 1.5 vs. 10.3 ± 2.6%, P < 0.01) and OW/OB AE-PCOS (5.2 ± 1.5 vs. 6.6 ± 0.9%, P = 0.048). A negative correlation between BSL %FMD and free testosterone was observed in lean AE-PCOS only (R² = 0.68, P = 0.02). EE increased %FMD in both OW/OB groups (CTRL: 7.6 ± 0.6 vs. 10.4 ± 2.5%, AE-PCOS: 6.6 ± 0.9 vs. 9.6 ± 1.7%, P < 0.01), had no impact on %FMD in lean AE-PCOS (5.17 ± 1.5 vs. 5.17 ± 1.1%, P = 0.99), and reduced %FMD in lean CTRL (10.3 ± 2.6 vs. 7.6 ± 1.2%, P = 0.03). Collectively, these data indicate that lean women with AE-PCOS exhibit more severe endothelial dysfunction than their OW/OB counterparts. Furthermore, endothelial dysfunction appears to be mediated by circulating androgens in lean but not in OW/OB AE-PCOS, suggesting a difference in the endothelial pathophysiology of AE-PCOS between these phenotypes.NEW & NOTEWORTHY We present evidence for marked endothelial dysfunction in lean women with androgen excess polycystic ovary syndrome (AE-PCOS) that is 1) associated with free testosterone levels, 2) impaired relative to overweight/obese women with AE-PCOS, and 3) unchanged following short-term ethinyl estradiol supplementation. These data indicate an important direct effect of androgens on the vascular system in women with AE-PCOS. Our data also suggest that the relationship between androgens and vascular health differs between phenotypes of AE-PCOS.

Slow-Speed Low-Intensity but Not Normal-Speed High-Intensity Resistance Exercise Maintains Endothelial Function

Purpose: High-intensity resistance exercise two or three times a week has been considered optimal for muscle hypertrophy, although it can remarkably elevate blood pressure (BP). In contrast, slow-speed resistance exercise with low intensity and tonic force generation (slow-low) can induce muscle hypertrophy without elevating BP. However, it is unclear how endothelial function changes after slow-low. Therefore, this study examined whether slow-low would maintain brachial artery endothelial function in comparison with normal-speed with high intensity resistance exercise (normal-high) and normal-speed with low-intensity resistance exercise (normal-low). Methods: Eleven healthy young men performed leg-extensions with slow-low (3 sets of 8 repetitions at 50% of 1RM), normal-high (3 sets of 8 repetitions at 80% of 1RM), and normal-low (3 sets of 8 repetitions at 50% of 1RM). Flow-mediated dilation (FMD) in the brachial artery was evaluated at pre-exercise and at 10, 30, and 60 min after exercise. Result: The results showed that normal-high caused significant impairment of FMD at 30 (3.7 ± 2.7%) and 60 (3.7 ± 2.8%) min after exercise (P < .05). In contrast, slow-low and normal-low showed no significant difference from baseline. FMD was significantly lower in normal-high compared with slow-low and normal-low at 30 and 60 min after exercise (P < .05). Additionally, systolic BP was significantly higher during normal-high compared with slow-low and normal-low (P < .05). Conclusion: We concluded that slow-low did not impair brachial artery FMD concomitant with lower systolic BP, and may therefore be a useful mode of exercise training to improve muscle hypertrophy without provoking transient endothelial dysfunction.

What is the impact of aerobic fitness and movement interventions on low-flow-mediated vasoconstriction? A systematic review of observational and intervention studies

The cardiovascular benefits of physical exercise are well established. The vasoreactivity that occurs during reductions in local arterial blood flow, termed low-flow-mediated constriction (L-FMC), is a measure of endothelial-dependent vasoconstrictor function. It is unclear whether aerobic fitness and movement (or lack thereof) influences L-FMC. We systematically reviewed studies examining the impact of physical behaviours on L-FMC. To be included, cross-sectional and interventional studies had to examine the impact of a physical behaviour on L-FMC in adults. There were no language or date of publication restrictions. Sources were searched in May, 2021 and included Scopus, Embase, MEDLINE, CINAHL, and Academic Search Premier. National Institutes of Health quality assessment tools were used. Fourteen studies (15 arms; 313 participants; 398 total observations from four arteries) met the inclusion criteria. The study quality varied from four out of 14 (controlled intervention scoring) to nine out of 12 (longitudinal intervention with no control group scoring) with the total points dependent upon the study design. Conflicting results were reported for acute prolonged sitting studies (attenuated L-FMC: n = 1; no change: n = 1) and resistance exercise (increased L-FMC: n = 2; no change: n = 2). Most observational studies examining aerobic fitness (3/4 studies) and aerobic exercise interventions (4/5 studies) observed a favourable effect on L-FMC. Overall, the included studies support that higher aerobic fitness and engaging in aerobic exercise training may augment L-FMC responses. Our systematic review highlights the heterogeneity between studies and identifies current gaps and future directions to better our understanding of (in)activity, exercise, and posture on endothelial vasoconstrictor function. PROSPERO Registration No.: CRD42021248241.

Aging-Related Moderation of the Link Between Compliance With International Physical Activity Recommendations and the Hemodynamic, Structural, and Functional Arterial Status of 3,619 Subjects Aged 3–90 Years

Background

Compliance with physical activity recommendations (CPARs) is associated with better health indicators. However, there are only few studies to date that have comprehensively analyzed the association between CPARs and cardiovascular status “as a whole” (e.g., analyzing hemodynamic, structural, and functional properties, and different arterial territories). The relationship between CPARs and cardiovascular properties could be strongly influenced by the growth and aging process.

Aim

The goal of the study is to investigate the association between CPAR and cardiovascular properties by placing special emphasis on: (i) identifying if there is an independent association, (ii) if the association is “moderated” by age, and (iii) to what extent the association depends on the arterial parameter (hemodynamic vs. structural vs. functional) and/or the arterial segment (e.g., central vs. peripheral; elastic vs. transitional vs. muscular arteries).

Methods

A total of 3,619 subjects (3–90 years of age) were studied. Extensive cardiovascular evaluations were performed. Cardiovascular risk factors (CRFs) and physical activity (PA) levels were determined. The subjects were categorized as compliant (n = 1, 969) or non-compliant (n = 1,650) with World Health Organization-related PA recommendations. Correlation and multiple regression models (including CPAR^*Age interaction) were obtained, and Johnson-Neyman technique was used to produce regions of significance.

Results

The independent association between CPARs and cardiovascular characteristics were strongly moderated by age. The moderation was observed on a wide range of age but particularly notorious on the extremes of life. Certain arterial characteristics demonstrated opposite effects in relation to CPAR status depending on the range of age considered. The association between CPAR and cardiovascular characteristics was independent of CRFs and moderated by age. In subjects younger than 45–55 years, CPAR status was associated with lower central and peripheral blood pressure (i.e., the younger the subject, the higher the reduction). During adult life, as age increases in the subjects, CPARs was associated with a beneficial hemodynamic profile, which is not related with variations in pressure but strongly related with lower levels of waveform-derived indexes and ventricular afterload determinants.

Conclusions

The independent associations between CPARs and arterial properties were strongly moderated by age. Data provided by blood pressure levels and waveform-derived indexes would be enough to evaluate the independent association between CPARs and the vascular system in the general population.

Central Blood Pressure and Subclinical Atherosclerotic Risk in Young Hispanic American Women

Background

The incidence of younger women being hospitalized from cardiovascular disease (CVD) events is on the rise. Hispanic women are generally thought to have higher CVD risk factor burden than non-Hispanic White (NHW) women yet Hispanic Americans have lower mortality from CVD. Traditional measures of CVD may not accurately capture CVD risk in Hispanic Americans. Hence, the purpose of this study was to assess the impact of ethnicity on vascular reactivity and central hemodynamic load to gain insight into subclinical CVD risk in young women.

Methods

Brachial flow-mediated dilation (FMD), low-flow mediated constriction (L-FMC), carotid-femoral pulse wave velocity (cfPWV), and pulse wave analysis (from synthesized aortic pressure waveforms) were measured in 25 Hispanic women and 31 NHW women aged between 18-35 years. FMD and L-FMC were combined to provide an index of total vessel reactivity.

Results

NHW and Hispanic women did not differ in age or traditional CVD risk factors (P>.05 for all). Compared with NHW women, Hispanic women had greater vascular reactivity (8.7±4.1 vs 11.7±4.1 %, P=.011), lower central pulse pressure (28±5 vs 24±3 mm Hg, P=.001) and lower pressure from wave reflections (12±2 vs 10±1 mm Hg, P=.001). There were no differences in cfPWV between NHW women and Hispanic women (5.4±0.7 vs 5.3±0.7 m/s, P=.73).

Conclusion

Young Hispanic women have greater vascular reactivity and lower central pulsatile hemodynamic load compared with NHW women, suggesting lower subclinical CVD risk.

A larger low-flow-mediated constrictor response is associated with augmented flow-mediated dilation in the popliteal artery

In the brachial artery, conflicting evidence exists regarding the relationship between the low-flow-mediated constriction (L-FMC) and subsequent flow-mediated dilation (FMD) responses, which may confound interpretation of the latter. The popliteal artery is a common site for atherosclerotic development, which is preceded by endothelial dysfunction. We aimed to determine whether the magnitude of popliteal L-FMC impacted FMD responses, which is currently unknown. L-FMC and FMD were assessed in the popliteal artery via high-resolution duplex ultrasonography and quantified as the percent change in diameter (from baseline) during ischaemia and in response to hyperaemia, respectively. Using partial correlations and multiple regression analyses, we evaluated the association between popliteal L-FMC on FMD in 110 healthy participants (60 females; 42 ± 22 [19-77] years). All variables univariately associated (p < 0.05) with popliteal relative FMD (relative L-FMC, log-SR_AUC , age, systolic blood pressure, diastolic blood pressure, resting shear rate) were inputted into a model that explained 35% of the variance. The reactive hyperaemia stimulus (log-SR_AUC : β = 1.10) and relative L-FMC (β = -0.39) were the only independent predictors of FMD (both, p < 0.01). Relative L-FMC was negatively correlated to relative FMD, after controlling for the significant univariate predictor variables listed above (R = -0.30; p = 0.002). An augmented (ie healthier) L-FMC response was linked with a larger FMD response as determined by the independent inverse association observed between these shear-stress-mediated measures of vasoreactivity.

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.

Effects of clopidogrel vs. prasugrel vs. ticagrelor on endothelial function, inflammatory parameters, and platelet function in patients with acute coronary syndrome undergoing coronary artery stenting: a randomized, blinded, parallel study

AIMS

In a randomized, parallel, blinded study, we investigate the impact of clopidogrel, prasugrel, or ticagrelor on peripheral endothelial function in patients undergoing stenting for an acute coronary syndrome.

METHODS AND RESULTS

The primary endpoint of the study was the change in endothelium-dependent flow-mediated dilation (FMD) following stenting. A total of 90 patients (age 62 ± 9 years, 81 males, 22 diabetics, 49 non-ST elevation myocardial infarctions) were enrolled. There were no significant differences among groups in any clinical parameter. Acutely before stenting, all three drugs improved FMD without differences between groups (P = 0.73). Stenting blunted FMD in the clopidogrel and ticagrelor group (both P < 0.01), but not in the prasugrel group. During follow-up, prasugrel was superior to clopidogrel [mean difference 2.13, 95% confidence interval (CI) 0.68-3.58; P = 0.0047] and ticagrelor (mean difference 1.57, 95% CI 0.31-2.83; P = 0.0155), but this difference was limited to patients who received the study therapy 2 h before stenting. Ticagrelor was not significantly superior to clopidogrel (mean difference 0.55, 95% CI -0.73 to 1.82; P = 0.39). No significant differences were seen among groups for low-flow-mediated dilation. Plasma interleukin (IL)-6 (P = 0.02 and P = 0.01, respectively) and platelet aggregation reactivity in response to adenosine diphosphate (P = 0.002 and P = 0.035) were lower in the prasugrel compared to clopidogrel and ticagrelor group.

CONCLUSION

As compared to ticagrelor and clopidogrel, therapy with prasugrel in patients undergoing stenting for an acute coronary syndrome is associated with improved endothelial function, stronger platelet inhibition, and reduced IL-6 levels, all of which may have prognostic implications. This effect was lost in patients who received the study medication immediately after stenting.

EUDRACT-NO

2011-005305-73.

Exercise modality, but not exercise training, alters the acute effect of exercise on endothelial function in healthy men

We used a within-subject crossover design to examine the impact of exercise modality, i.e., resistance (RT) and endurance (END), on the acute impact of exercise on endothelial function. Then, we examined whether a 4-wk period of chronic exercise training altered the acute exercise-induced change in endothelial function in healthy individuals. Thirty-four healthy, young men (21 ± 2 yr) reported to our laboratory and completed assessment of endothelial function [using the brachial artery flow-mediated dilation test (FMD)] before and immediately after a single bout of RT (leg-extension) or END (cycling). Subsequently, participants completed a 4-wk period of training (12 sessions), followed by evaluation of the FMD before and after a single bout of exercise. Following a 3-wk washout, participants repeated these experiments with the different exercise modality (in a balanced crossover design). An exercise × modality interaction effect was found (P < 0.001). Post hoc pairwise analyses revealed a decrease in FMD after END (P < 0.001) but not after RT (P = 0.06). Four weeks of exercise training improved resting FMD after END and RT (P = 0.04) but did not alter the acute effect of exercise on FMD (exercise × modality × training effect: P = 0.63), an effect independent of the modality of exercise (exercise × training interaction: P = 0.46 and P = 0.11 in RT and END, respectively). These distinct changes in FMD following acute exercise may relate to the different prolonged physiological responses induced by endurance versus resistance exercise. Specifically, endurance exercise, but not resistance exercise, causes a decrease in brachial artery endothelial function, which was unaffected by 4 wk of chronic exercise training.NEW & NOTEWORTHY We found that resistance and endurance exercise modalities lead to different endothelial function responses after a single bout of exercise. Endothelial function increased after an acute bout of resistance exercise, whereas it decreased after an acute bout of endurance exercise. Four weeks of chronic exercise training did not affect the acute endothelial function response.

Endothelial function of healthy adults from 20 to 91 years of age: prediction of cardiovascular risk by vasoactive range

OBJECTIVES

Brachial arterial low flow-mediated constriction (L-FMC) and flow-mediated dilation (FMD) are ultrasound-based biomarkers that emerge into scientific and clinical practice indicating cardiovascular effects of medical and lifestyle-based treatment beyond classical risk factors. This study is the first to provide reference values and to assess the predictive value of L-FMC, FMD and their composite endpoint vasoactive range (VAR) in healthy adults.

METHODS

L-FMC, FMD and VAR were measured in 457 nonsmoking adults of 20-91 years without chronic diseases, medication, with normal heart function and very low cardiovascular risk. Sex-specific percentiles were calculated and predictive ability for elevated cardiovascular risk was assessed using receiver-operating characteristic (ROC) curves.

RESULTS

From 20 to 91 years of age, L-FMC increased 86.1 and 105.3%, FMD decreased 63.6 and 47.1% and VAR decreased 58.3 and 55.2% in women and men, respectively. Area under the ROC curves was 0.54 (95% CI = 0.49-0.54) for L-FMC, 0.67 (95% CI = 0.62-0.67) for FMD and 0.72 (95% CI = 0.67-0.72) for VAR (P < 0.001). Discriminatory cut-offs for elevated risk were 0.24% for L-FMC (sensitivity = 0.42, specificity = 0.67), 6.4% for FMD (sensitivity = 0.71, specificity = 0.60) and 6.3% for VAR (sensitivity = 0.62, specificity = 0.73).

CONCLUSION

This study demonstrates reduced endothelial function with aging in healthy men and women with very low cardiovascular risk. Percentiles crossed cut-offs for elevated cardiovascular risk between 50 and 55 years in men and 70 and 75 years in women, indicating higher risk for cardiovascular disease in men. VAR showed the highest ability to identify individuals with elevated cardiovascular risk, and should be included in the monitoring and treatment of accelerated vascular aging even in healthy individuals.

Influence of prostaglandins and endothelial-derived hyperpolarizing factors on brachial and popliteal endothelial-dependent function in young adults

Heterogeneous flow-mediated dilation (FMD) and low-flow-mediated constriction (L-FMC) responses have been reported between upper- and lower-limb arteries. Radial artery L-FMC, but not FMD, responses are blunted when endothelial-derived hyperpolarizing factors (EDHFs) or prostaglandin production is inhibited in young adults. However, it is unknown if these mechanisms similarly impact endothelial-dependent responses in the brachial (BA) and popliteal (POP) arteries. We tested whether BA- and POP-L-FMC and FMD would be influenced by independent EDHF and prostaglandin inhibition. Eighteen participants (23 ± 3 yr; 6♀) completed three randomized and double-blinded ultrasound assessments following ingestion of an opaque capsule containing maltodextrin (control), 150 mg of fluconazole (EDHF inhibition), or 500 mg of aspirin (prostaglandin inhibition). POP resting diameter was reduced following fluconazole administration (6.13 ± 0.63 mm vs. 6.19 ± 0.65 mm in control, P = 0.03). Compared with control, fluconazole also blunted the relative L-FMC responses in both the BA (-2.1 ± 0.8% vs. -0.8 ± 1.0%, P = 0.001) and POP (-1.7 ± 1.1% vs. -0.8 ± 0.9%, P = 0.009). In contrast, aspirin did not impact either the BA (-1.9 ± 0.7%) or POP-L-FMC (-1.3 ± 0.6%) responses (both, P > 0.35). The FMD response was unchanged following fluconazole or aspirin administration in either artery (both, P > 0.36). Our findings demonstrate that EDHF mediates L-FMC responses in both the brachial and popliteal arteries. Complementary to the nitric oxide-mediated FMD response, L-FMC appears to provide information regarding the EDHF pathway. Future research should uncover if these mechanisms impact older adults and/or patient populations characterized by vascular endothelial dysfunction associated with low aerobic fitness and habitual physical activity levels.NEW & NOTEWORTHY We compared changes in upper- and lower-limb artery endothelial-dependent vasodilatory and vasoconstrictor responses between control, prostaglandin inhibition, and endothelial-derived hyperpolarizing factor inhibition conditions. Neither prostaglandins nor endothelial-derived hyperpolarizing factor influenced flow-mediated dilation responses in either the brachial or popliteal artery. In contrast, endothelial-derived hyperpolarizing factor, but not prostaglandins, reduced resting brachial artery blood flow and shear rate and resting popliteal artery diameter, as well as low-flow-mediated constriction responses in both the popliteal and brachial arteries.

The impact of age and sex on popliteal artery endothelial-dependent vasodilator and vasoconstrictor function

Lower-limb arteries, such as the popliteal artery, are a common site of atherosclerosis. These arteries are habitually exposed to large fluctuations in blood flow during physical and sedentary activities. Low-flow-mediated constriction (L-FMC) and flow-mediated dilation (FMD) provide indices of endothelial-dependent vasoconstriction and vasodilation, respectively. Age and sex both impact upper-limb FMD. However, it is unclear whether these factors also influence popliteal endothelial-dependent function. Popliteal endothelial function was compared between younger and older males and females (n=14 per group) matched for age- and sex-specific relative aerobic fitness levels (each group's normative percentile: ~45%). Nitroglycerin-mediated dilation (NMD) was also assessed as a measure of endothelial-independent vasodilation. Ageing reduced relative popliteal FMD in both males (older: 4.3±1.8% versus younger 5.7±1.9%) and females (older: 2.9±1.8% versus younger: 6.1±1.6%, both: P<0.046). FMD was also lower in older females versus older males (P=0.04). Popliteal NMD findings followed the same pattern as FMD. Compared to younger adults, relative L-FMC responses were blunted among older males (older: -1.2±1.1% versus younger: -2.2±1.0%) and females (older: -1.0±1.2% versus younger: -2.1±1.3%, both P<0.03) with no sex-differences observed in either age group (all, P>0.60). The adverse age- and sex-related (older adults only) declines in popliteal FMD were mediated, in part, by reduced vascular smooth muscle sensitivity to nitric oxide. Endothelial-dependent vasoconstriction was also attenuated with age, but unaffected by sex. Despite similar normative aerobic fitness percentiles (~45%), older adults exhibited attenuated popliteal endothelial function than their younger counterparts. This was particularly evident in older females who exhibited the lowest endothelial-dependent vasodilatory responses.

Impact of whole body passive heat stress and arterial shear rate modification on radial artery function in young men

We sought to determine how whole body heating acutely influences radial artery function, characterized using flow-mediated dilation (FMD) and low-flow-mediated constriction (L-FMC), and the mechanistic role of shear rate modification on radial artery functional characteristics during heating. Eleven young healthy men underwent whole body heating (water-perfused suit) sufficient to raise the core temperature by +1°C. Trials were repeated with (heat + WC) and without (heat) the application of a wrist cuff located distal to the radial artery examined, known to prevent increases in mean and anterograde shear rates but increase retrograde shear rate. Radial artery characteristics were assessed throughout each trial, with FMD and L-FMC assessed before and upon reaching the target core temperature. Heat markedly increased radial artery mean and anterograde shear rates, along with radial artery diameter and blood flow (P < 0.05). Heat + WC abolished the heat-induced increase in mean and anterograde shear rates (P > 0.05) but markedly increased retrograde shear rate (P < 0.05). Concomitantly, increases in radial artery diameter and blood flow were decreased (heat + WC vs. heat, P < 0.05). Heat attenuated FMD (8.6 ± 1.2% vs. 2.2 ± 1.4%, P < 0.05), whereas no change in FMD was observed in heat + WC (7.8 ± 1.2% vs. 10.8 ± 1.2%, P > 0.05). In contrast, L-FMC was not different in either trial (P > 0.05). In summary, acute whole body heating markedly elevates radial artery shear rate, diameter, and blood flow and diminishes FMD. However, marked radial artery vasodilation and diminished FMD are absent when these shear rate changes are prevented. Shear rate modifications underpin the radial artery response to acute whole body heat stress, but further endothelium-dependent vasodilation (FMD) is attenuated likely as the vasodilatory range limit is approached.NEW & NOTEWORTHY We observed that acute whole body heating elevates radial artery shear rate, diameter, and blood flow. This results in a diminished flow-meditated dilatation (FMD) but does not change low-flow-mediated constriction (L-FMC). Preventing shear rate changes during whole body heating reduces radial artery vasodilation and reverses FMD reductions but has no effect on L-FMC. These findings indicate that shear rate changes underpin conduit artery responses to acute whole body heat stress, but further endothelium-dependent flow-mediated vasodilation is attenuated as the vasodilatory range limit is approached.

Overview of the Assessment of Endothelial Function in Humans

The endothelium is recognized to play an important role in various physiological functions including vascular tone, permeability, anticoagulation, and angiogenesis. Endothelial dysfunction is increasingly recognized to contribute to pathophysiology of many disease states, and depending on the disease stimuli, mechanisms underlying the endothelial dysfunction may be markedly different. As such, numerous techniques to measure different aspects of endothelial dysfunction have been developed and refined as available technology improves. Current available reviews on quantifying endothelial dysfunction generally concentrate on a single aspect of endothelial function, although diseases may affect more than one aspect of endothelial function. Here, we aim to provide an overview on the techniques available for the assessment of the different aspects of endothelial function in humans, human tissues or cells, namely vascular tone modulation, permeability, anticoagulation and fibrinolysis, and the use of endothelial biomarkers as predictors of outcomes.

Maintenance of endothelial function following acute resistance exercise in females is associated with a tempered blood pressure response

Acute resistance exercise-induced hypertensive stimulus impairs endothelial function in males. Because prior work indicates that female subjects have a tempered blood pressure response to acute resistance exercise, we hypothesized that, compared with males, females would better maintain endothelial function following resistance exercise and that this preservation would be associated with a lower hypertensive stimulus. Twenty-nine young healthy males (n = 16) and females (n = 13) participated in this study. All subjects performed a session of resistance exercise (leg extension) at the same relative workload [65% of one repetition maximum (1RM)]. The blood pressure response to exercise was characterized, and brachial artery flow-mediated dilation (FMD) was measured before and after. Males performed a second experimental trial in which the blood pressure response to resistance exercise was matched to that of females. This was accomplished by reducing the workload (~25% of 1RM). When resistance exercise was performed at the same relative workload, the systolic blood pressure was greater in males compared with females. Congruently, resistance exercise caused a significant impairment in FMD in males but not in females (P < 0.001). When the exercise workload was reduced in males, they no longer displayed an impairment in FMD following resistance exercise and, as such, the sex difference was abolished (P > 0.05). The present study reveals that acute resistance exercise transiently impairs endothelial function in young, healthy males but not in age-matched females. Notably, the maintenance of endothelial function in females is associated with a lower blood pressure response during resistance exercise.NEW & NOTEWORTHY The present data demonstrate for the first time that acute resistance exercise impairs endothelial function in young, healthy male but not female subjects. In addition, we show that the preservation of endothelial function in females is associated with a mitigated blood pressure response during resistance exercise. Accordingly, this work portrays a sexual dimorphism in the barostress response, and ensuing vascular effects, to resistance exercise.

The Low-Flow-Mediated Arterial Constriction in the Upper Limbs of Healthy Human Subjects are Artery Specific and Handedness Independent

Low-flow-mediated constriction (LFMC) has been used to assess resting endothelial function in peripheral conduit arteries. The literature describes discrepancies in the behaviour of radial versus brachial artery in response to low-flow state, the reasons for which were not addressed in a systematic and scientific way. Moreover, the influence of handedness on observed LFMC responses has not been investigated. The present study aimed at systematic measurement and comparison of the LFMC responses in radial and brachial arteries of both dominant and non-dominant arms of healthy human volunteers. We also investigated the physiological factors associated with differential LFMC response of radial versus brachial artery in the same group of subjects. Longitudinal B mode ultrasonographic cine loops of radial and brachial arteries were acquired at baseline and after producing distal circulatory arrest. Cine loops were screen grabbed and analyzed later using automated edge detection algorithms to measure end-diastolic diameters. Distal circulatory arrest was produced over the proximal forearm (for the brachial artery) and over the wrist (for the radial artery) at 250 mm Hg for 5 min after baseline measurements. Results suggested that arterial location (p = 0.0001) and baseline diameter (p < 0.0021) emerged as independent predictors of LFMC response. Differences in the LFMC responses are handedness independent and could be attributed to the arterial location along with the differences in their baseline diameters.

Post-exercise Endothelium-Dependent Vasodilation Is Dependent on Training Status

The effect of training status on post-exercise flow-mediated dilation (FMD) is not well characterized. We tested the hypothesis that the more trained the subjects, the lower the reduction in FMD after an acute bout of aerobic exercise. Forty-seven men (mean ± SD, age: 20.1 ± 1.2 years, body mass: 75.5 ± 5.1 kg, height 178.1 ± 5.4 cm) were divided into five groups with different training characteristics (sedentary, two different groups of active subjects, two different groups of well-trained subjects - runners and weightlifters). Brachial artery FMD (blood pressure cuff placed around the arm distal to the probe with the proximal border adjacent to the medial epicondyle; 5 min at a pressure of 220 mmHg) was assessed before and during 3 min immediately after a bout of cycling exercise at a relative intensity of 170 bpm [(physical work capacity (PWC₁₇₀)]. At baseline, a progressive increase in FMD was observed in the participants with the higher training status, if the training remained moderate. Indeed, FMD was reduced in runners and weightlifters compared to those who were moderately trained. After PWC₁₇₀, FMD did not significantly change in sedentary and highly trained runners, significantly increased in the two groups of active subjects but significantly decreased in highly trained weightlifters. These results showed that endothelium-dependent vasodilation evaluated using brachial FMD is maintained or improved following acute aerobic exercise in moderately trained participants, but not in well-trained participants, especially if they are engaged in resistance training.

Effects of Grape Seed Proanthocyanidin Extract on Vascular Endothelial Function in Participants with Prehypertension: A Randomized, Double-Blind, Placebo-Controlled Study

This study aimed to investigate the effects of grape seed proanthocyanidin extract (GSPE) on blood pressure and vascular endothelial function in middle-aged Japanese adults with prehypertension. We conducted a randomized, double-blind, placebo-controlled study on 6 men and 24 women aged 40-64 years old. The participants were randomized to receive tablets containing either low-dose (200 mg/day) or high-dose (400 mg/day) GSPE, or placebo, for 12 weeks. Systolic and diastolic blood pressures (SBP and DBP, respectively), brachial flow-mediated dilation (FMD), and other cardiovascular parameters were measured before and after 4, 8, and 12 weeks of treatment. The mean SBP in the high-dose group significantly decreased by 13 mmHg after 12 weeks (P = 0.028), although FMD did not change. In an ad hoc analysis of non-smoking participants (n = 21), the mean SBP, DBP, stiffness parameter β, distensibility, incremental elastic modulus (Einc), and pulse wave velocity (PWV) also significantly improved in the high-dose group after 12 weeks. Changes in Einc and PWV from baseline to 12 weeks were significantly greater in the high-dose group than in the placebo group (Einc, P = 0.023; PWV, P = 0.03). GSPE consumption could help maintain vascular elasticity and normal blood pressure in this population.

Sex does not influence impairments in popliteal endothelial-dependent vasodilator or vasoconstrictor responses following prolonged sitting

An acute bout of prolonged sitting (PS) impairs the popliteal artery flow-mediated dilation (FMD) response. Despite equivocal reductions in mean shear rate, young women demonstrate an attenuated decline in popliteal FMD versus young men. However, it is uncertain whether popliteal endothelial-dependent vasoconstrictor responses [low-flow-mediated constriction (L-FMC)] are similarly affected by PS and/or whether sex differences exist. We tested the hypothesis that women would have attenuated reductions in both popliteal FMD and L-FMC responses following an acute bout of PS. Popliteal FMD and L-FMC responses were assessed via duplex ultrasonography before and after a 3-h bout of PS. These responses were then compared between 10 men (24 ± 2 yr) and 10 women (23 ± 2 yr) with similar ( P > 0.13) levels of objectively measured habitual physical activity (via PiezoRx) and sedentary time (via activPAL). At baseline, men and women exhibited similar ( P > 0.46) popliteal FMD (4.8 ± 1.2 vs. 4.5 ± 0.6%) and L-FMC (–1.7 ± 1.0 vs. –1.9 ± 0.9%) responses. Both sexes experienced identical (group: P > 0.76; time: P < 0.001) PS-induced impairments in popliteal FMD (–2.8 ± 1.4 vs. –2.6 ± 0.9%) and L-FMC (1.3 ± 0.7% vs. 1.4 ± 0.7%). In young adults, sex did not influence the negative PS-induced FMD, L-FMC, or microvascular responses in the lower limb. As such, our findings suggest that young men and women are similarly susceptible to the acute negative vascular effects of PS. Future studies should extend these findings to older, less physically active adults and/or patients with vascular disease.

NEW & NOTEWORTHY We compared changes in popliteal artery endothelial function to a single 3-h bout of sitting between young men and women. Both groups exhibited similar endothelial-dependent vasodilation (i.e., flow-mediated dilation) and endothelial-dependent vasoconstrictor responses (i.e., low-flow-mediated constriction) at baseline and equivocal impairments in these measures of endothelial function following prolonged sitting. These findings demonstrate that acute impairments in conduit artery endothelial health associated with uninterrupted sitting are not influenced by sex in young, healthy adults.

Resting and recruitable endothelial function - Evidence of two distinct circadian patterns

BACKGROUND

Evidence of a circadian rhythm in endothelium-dependent vasomotor function, with a nadir in Flow-Mediated Dilation (FMD) in the early morning hours, has been previously reported. These changes have been proposed to be one of the mechanisms explaining the circadian pattern in the incidence of cardiovascular events. We set out to investigate the circadian rhythm of FMD, low-flow mediated dilation (L-FMC) and sympathetic vascular tone.

METHODS AND RESULTS

10 young healthy male volunteers (mean age, 28.9±3.7 years) underwent measurements of radial artery endothelium-dependent FMD and L-FMC at 8AM, 2PM and 8PM on the same day. Sympathetic vascular tone was assessed with laser Doppler and Fourier transform analysis. Compared with 2PM and 8PM, FMD decreased markedly in the early morning (2.9±3.4%; 6.2±2.9%; 6.0±4.0%; P = 0.007). In contrast, L-FMC was maximal at 8AM, decreased significantly at 2PM, and returned to higher values at 8PM (-5.1±1.3%; -2.7±2.0%; -4.6±2.2%; P = 0.030), such that the composite endpoint of endothelial function (sum of FMD+L-FMC) was not significantly different among timepoints. Vascular sympathetic tone was maximal early in the morning and lowest in the evening (P = 0.014) without a correlation with the changes in FMD or L-FMC.

CONCLUSIONS

Endothelial responsiveness (FMD) and basal tone (L-FMC) appear to follow different circadian rhythms, with an impaired responsiveness in the early morning and a nadir in baseline tone in the early afternoon.

Relationship between brachial and popliteal artery low-flow-mediated constriction in older adults: impact of aerobic fitness on vascular endothelial function

We previously observed that brachial artery (BA) low-flow-mediated constriction (L-FMC) is inversely related to aerobic fitness (i.e., V̇o2peak) in older adults (OA). However, it is unclear if an L-FMC response is elicited in the popliteal artery (POP) or if a similar inverse relationship with aerobic fitness exists. Considering that the POP experiences larger shear stress fluctuations during sedentary behaviors and traditional lower limb modes of aerobic exercise, we tested the hypotheses that 1) heterogeneous L-FMC responses exist between the BA versus POP of OA, and 2) that aerobic fitness will be inversely related to POP L-FMC. L-FMC was assessed in 47 healthy OA (30 women, 67 ± 5 yr) using duplex ultrasonography and quantified as the percent decrease in diameter (from baseline) during the last 30 s of a 5-min distal cuff occlusion period. When allometrically scaled to baseline diameter, the BA exhibited a greater L-FMC response than the POP (–1.3 ± 1.6 vs. –0.4 ± 1.6%; P = 0.03). Furthermore, L-FMC responses in the BA and POP were not correlated ( r = 0.22; P = 0.14). V̇o2peak was strongly correlated to POP L-FMC ( r = –0.73; P < 0.001). The heterogeneous BA versus POP L-FMC data indicate that upper limb L-FMC responses do not represent a systemic measure of endothelial-dependent vasoconstrictor capacity in OA. The strong association between V̇o2peak and POP L-FMC suggests that localized shear stress patterns, perhaps induced by lower limb dominant modes of aerobic exercise, may result in greater vasoconstrictor responsiveness in healthy OA.

NEW & NOTEWORTHY We compared low-flow-mediated constriction responses between the brachial and popliteal arteries of healthy older adults. Vasoconstrictor responses were not correlated between arteries. A strong relationship between aerobic fitness and low-flow-mediated vasoconstriction was observed in the popliteal artery. These findings suggest that brachial vasoconstrictor responsiveness is not reflective of the popliteal artery, which is exposed to larger shear stress fluctuations during bouts of sedentary behavior and traditional lower limb modes of exercise.

Association of Apical Periodontitis with Cardiovascular Disease via Noninvasive Assessment of Endothelial Function and Subclinical Atherosclerosis

INTRODUCTION

Chronic infections of endodontic origin might predispose to the onset of cardiovascular disease (CVD). The studies depicting the link between apical periodontitis (AP) and CVD are few, and the association is very controversial; also, the markers used are expensive, which makes them difficult to use in general practice. The purpose of this study was to investigate whether an association exists between AP and CVD using noninvasive methods (ie, flow-mediated dilatation [FMD] and carotid intima-media thickness [c-IMT]).

METHODS

This cross-sectional study included 120 men between 20 and 40 years old free from periodontal disease, CVD, and traditional cardiovascular risk factors; 60 subjects had AP, and 60 acted as controls. All subjects underwent complete physical and dental examination, echocardiography, ultrasound assessment of FMD of the right brachial artery, and c-IMT. Data were analyzed using the Mann-Whitney U test and the Spearman rank correlation (r_s) test.

RESULTS

FMD was found to be significantly impaired in patients with AP (mean = 4.9% ± 2.05%) compared with healthy controls (mean = 9.74% ± 2.59%, P = .000). The study also depicts statistically significant differences between c-IMT of the AP (mean = 0.64 ± 0.12 mm) and control (mean = 0.54 ± 0.08 mm) groups (P = .000). A significant inverse correlation between c-IMT and FMD was observed (r_s = -0.381, P = .000).

CONCLUSIONS

Impaired FMD and greater c-IMT in subjects with AP suggests a potential association between endodontic infection and CVD.

Reliability of low-flow vasoreactivity in the brachial artery of adolescents

PURPOSE

Macrovascular endothelial function is commonly assessed using flow-mediated dilation (FMD) and is nitric oxide (NO) dependent. However, the vasoreactivity to low flow during the FMD protocol may complement FMD interpretation. This study aimed to investigate in adolescents: (1) the day-to-day reliability of low-flow-mediated constriction (L-FMC) and composite vessel reactivity (CVR); and (2) the relationship between L-FMC and FMD.

METHODS

A retrospective analysis of data on 27 adolescents (14.3 ± 0.6 year, 12 males) was performed. Participants had two repeat measures, on separate days, of macrovascular function using high-resolution ultrasound for assessment of L-FMC, FMD, and CVR.

RESULTS

On average, the L-FMC response was vasoconstriction on both days (-0.59 ± 2.22% and -0.16 ± 1.50%, respectively). In contrast, an inconsistent response to low flow (vasoconstriction, dilation, or no change) was observed on an individual level. Cohen's Kappa revealed poor agreement for classifying the L-FMC measurement between visits (k = 0.04, P > .05). Assessment of the actual vessel diameter was robust with a coefficient of variation of 1.7% (baseline and peak) and 2.7% (low-flow). The between-day correlation coefficient between measures was r = .18, r = .96 and r = .52 for L-FMC, FMD, and CVR, respectively. No significant correlation between FMD and L-FMC was observed for either visit (r = -.06 and r = -.07, respectively; P > .05).

CONCLUSION

In adolescents, the low-flow vasoreactivity is inconsistent between days. Whereas the actual vessel diameter is reproducible, the measurement of L-FMC and CVR has poor between-day reliability compared to FMD. Finally, L-FMC, and FMD are not significantly correlated.

The relationship between aerobic fitness and low-flow-mediated constriction in older adults

PURPOSE

Aerobic fitness is directly related to favorable vasodilatory (i.e., flow-mediated dilation; FMD) and vasoconstrictor functions (i.e., low-flow-mediated constriction; L-FMC) in young adults. Furthermore, aerobically fit older adults (OA) have larger FMD responses than their less fit peers. However, the relationship between aerobic fitness and vasoconstrictor responsiveness is unknown in OA. We hypothesized that OA who are more aerobically fit will exhibit a greater L-FMC response than their less fit counterparts.

METHODS

Forty-seven healthy OA (67 ± 5 years) were divided into less (LF; n = 27) and more aerobically fit (MF; n = 20) groups based on peak oxygen consumption (VO₂peak). VO₂peak was determined from an incremental maximal cycle ergometer test via indirect calorimetry. FMD and L-FMC were assessed in the brachial artery via high-resolution duplex ultrasonography.

RESULTS

VO₂peak (18.3 ± 3.2 versus 29.1 ± 5.8 ml/kg/min; P < 0.001) and L-FMC were both greatest in the MF versus LF groups (-1.2 ± 0.9 vs. - 0.5 ± 0.6%; P = 0.01). Furthermore, the MF group had an enhanced FMD response (5.6 ± 1.5 versus 3.9 ± 1.2%; P < 0.001). In the pooled sample, there was a negative correlation (r = - 0.52; P < 0.001) between VO₂peak (22.9 ± 7.0 ml/kg/min) and L-FMC (-0.8 ± 0.8%).

CONCLUSIONS

In an older population, greater aerobic fitness was associated with a more favorable vasoconstrictor response to low-flow conditions. Interventional or longitudinal aerobic exercise training studies are warranted in this population to determine the impact of training-induced increases in VO₂peak on L-FMC.

High-intensity resistance exercise with low repetitions maintains endothelial function

Resistance exercise impairs endothelial function, and this impairment is thought to be mediated by sustained elevation in blood pressure. Herein, we tested the hypothesis that resistance exercise-induced endothelial dysfunction would be prevented by high-intensity resistance exercise with low repetitions. This type of resistance exercise is known to induce temporal elevation in blood pressure due to low repetitions and a long resting period between sets. Thirteen young healthy subjects completed three randomized experimental trials as follows: 1) moderate-intensity exercise with moderate repetitions (moderate-moderate trial), 2) low-intensity exercise with high repetitions (low-high trial), and 3) high-intensity exercise with low repetitions (high-low trial). After baseline brachial artery flow-mediated dilation (FMD) and blood pressure measurements, subjects performed resistance exercise according to the different types of trials. Thereafter, brachial artery FMD and blood pressure measurements were repeated 10, 30, and 60 min after the exercise. Exercise-induced increases in blood flow and shear rate were significantly lower in the high-low trial than in the other two trials ( P < 0.05). Although systolic blood pressures were significantly elevated after exercise in all trials ( P < 0.05), the magnitudes of rise in blood pressure increase were significantly lower in the high-low trial than in the moderate-moderate and low-high trials ( P < 0.05). Moderate-moderate and low-high trials caused a significant impairment in brachial artery FMD ( P < 0.05), which could be prevented through high-intensity resistance exercise with low repetitions (  > 0.05). In conclusion, endothelial function was maintained by conducting high-intensity resistance exercise with low repetitions. NEW & NOTEWORTHY Data from the present study reveal that high-intensity resistance exercise with low repetitions can maintain endothelial function. Thus, this study provides the first evidence that the detrimental vascular effects of resistance exercise are preventable when resistance exercise is performed in high intensity with low repetitions. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/type-of-resistance-exercise-and-endothelial-function/ (Japanese version: https://ajpheart.podbean.com/e/japanese-language-podcast-type-of-resistance-exercise-and-endothelial-function/ ).

Impact of acute dynamic exercise on radial artery low-flow mediated constriction in humans

Purpose

A “low-flow mediated constriction” (L-FMC) is evoked in the radial artery by the inflation of an ipsilateral wrist cuff to a supra-systolic pressure. We sought to test the hypothesis that the radial artery L-FMC response is augmented immediately following acute dynamic leg exercise in young healthy individuals.

Methods

Ten healthy and recreationally active men (23 ± 4 years) undertook a 30-min trial of incremental dynamic leg cycling exercise (10 min at 50, 100 and 150 W) and a 30-min time control trial (seated rest). Trials were randomly assigned and performed on separate days. Radial artery characteristics (diameter, blood flow and shear rate) were assessed throughout each trial, with L-FMC and flow-mediated vasodilatation (FMD) assessments conducted prior to and immediately following (10 min) trials.

Results

Dynamic leg cycling exercise increased radial artery blood flow, along with mean, retrograde and anterograde shear rate (P < 0.05). Blood flow profiles were unchanged during the time control trial (P > 0.05). Following exercise L-FMC was increased (mean [SD]; − 5.6 [3.3] vs. − 10.1 [3.8] %, P < 0.05), while it was not different in the time control condition (− 8.1 [3.2] vs. − 6.7 [3.4] %, P > 0.05). FMD was not different following either the exercise or time control trials (P > 0.05), but the composite end-point of L-FMC + FMD was enhanced post-exercise (P < 0.05).

Conclusions

Dynamic exercise with a large muscle mass acutely augments the vasoconstrictor response of the radial artery in response to a reduction in blood flow (L-FMC) in young healthy individuals. The time course of this post-exercise response and the underlying vasoregulatory mechanisms require elucidation.

Acute exhaustive rowing exercise reduces skin microvascular dilator function in young adult rowing athletes

PURPOSE

The effect of acute exhaustive exercise session on skin microvascular reactivity was assessed in professional rowers and sedentary subjects. A potential involvement of altered hemodynamic parameters and/or oxidative stress level in the regulation of skin microvascular blood flow by acute exercise were determined.

METHODS

Anthropometric, biochemical, and hemodynamic parameters were measured in 18 young healthy sedentary men and 20 professional rowers who underwent a single acute exercise session. Post-occlusive reactive hyperemia (PORH), endothelium-dependent acetylcholine (ACh), and endothelium-independent sodium nitroprusside (SNP) microvascular responses were assessed by laser Doppler flowmetry in skin microcirculation before and after acute exercise. Serum lipid peroxidation products and plasma antioxidant capacity were measured using spectrophotometry.

RESULTS

At baseline, rowers had significantly lower diastolic blood pressure (DBP) and heart rate (HR), and higher stroke volume (SV), PORH, and endothelium-dependent vasodilation than sedentary. Acute exercise caused a significant increase in systolic blood pressure, DBP, HR, and SV and a decrease in total peripheral resistance in both groups. Acute exercise induced a significant impairment in PORH and ACh-induced response in rowers, but not in sedentary, whereas the SNP-induced vasodilation was not affected by acute exercise in any group. Antioxidant capacity significantly increased only in sedentary after acute exercise.

CONCLUSION

Single acute exercise session impaired microvascular reactivity and endothelial function in rowers but not in sedentary, possibly due to (1) more rowing grades and higher exercise intensity achieved by rowers; (2) a higher increase in arterial pressure in rowers than in sedentary men; and (3) a lower antioxidant capacity in rowers.

Hypertension during Weight Lifting Reduces Flow-Mediated Dilation in Nonathletes

PURPOSE

The purpose of this study was to determine whether increased intraluminal pressure is the damaging factor that reduces flow-mediated dilation (FMD) in young, healthy subjects after resistance exercise to maximal exertion.

HYPOTHESIS

Attenuating the rise in brachial artery pressure during weight lifting by placing a blood pressure cuff on the upper arm prevents postexercise impairment of brachial artery FMD in sedentary individuals.

METHODS

Nine sedentary individuals who exercise once a week or less and six exercise-trained individuals who exercise three times a week or more performed leg press exercise to maximal exertion on two separate occasions. During one visit, a blood pressure cuff, proximal to the site of brachial artery measurement, was inflated to 100 mm Hg to protect the distal vasculature from the rise in intraluminal pressure, which occurs during resistance exercise. Brachial artery FMD was determined using ultrasonography before and 30 min after weight lifting.

RESULTS

Without the protective cuff, brachial artery FMD in sedentary individuals was reduced after weight lifting (9.0% ± 1.2% prelift vs 6.6% ± 0.8% postlift; P = 0.005), whereas in exercise-trained individuals, FMD was unchanged (7.4% ± 0.7% prelift vs 8.0% ± 0.9% postlift; P = 0.543). With the protective cuff, FMD no longer decreased but rather increased in sedentary individuals (8.7% ± 1.2% prelift vs 10.5% ± 1.0% postlift, P = 0.025). An increase in FMD was also seen in exercise-trained subjects when the cuff was present (6.6% ± 0.7% prelift vs 10.9% ± 1.5% postlift, P < 0.001).

CONCLUSION

Protecting the brachial artery from exercise-induced hypertension enhances FMD in sedentary and exercise-trained individuals. These results indicate that increased intraluminal pressure in the artery contributes to the reduced FMD after heavy resistance exercise in sedentary individuals.

Intra- and inter-day reproducibility of low-flow mediated constriction response in young adults

PURPOSE

When assessing brachial endothelial function by reactive hyperaemia, stopping blood flow creates a period of low-flow-mediated constriction (L-FMC). As little is known about how this parameter influences flow-mediated vasodilation (FMD), the purpose of this study was to better understand this relationship and to determine the intra- and interday reproducibility of brachial L-FMC.

METHODS

Brachial L-FMC and FMD were measured on 26 healthy, young adults (13 males, 13 females; 24·6 ± 2·7 years). Each participant had two assessments conducted on two separate visits, separated by a minimum of seven days. Brachial artery baseline diameter was imaged during rest. Continuous imaging of the artery was performed during the last 20 s of cuff-occlusion to 180 s postcuff release. An L-FMC was considered present if the relative change from pre-occlusion baseline to L-FMC artery diameter was less than -0·1%.

RESULTS

Overall, there was a strong, positive correlation between increased brachial L-FMC and blunted FMD (visit 1 test 1: r = 0·758, P<0·001; visit 1 test 2: r = 0·706, P<0·001; visit 2 test 1: r = 0·836, P<0·001; visit 2 test 2: r = 0·857, P<0·001). The reproducibility of intra- and interday L-FMC diameter was intraclass correlation coefficients (ICC) = 0·627, coefficient of variation (CV) = 54·4% and ICC = 0·734, CV = 43·5%, respectively.

CONCLUSION

Vasoconstriction to low-flow conditions influences the subsequent maximal dilation during reactive hyperaemia. However, L-FMC is variable as evidenced by the weak intra- and interday reproducibility of the measure. Further research should study brachial L-FMC reproducibility among varying populations and the implications L-FMC has on the interpretation of FMD results.

Short-term high salt intake reduces brachial artery and microvascular function in the absence of changes in blood pressure

OBJECTIVES

The aims of this study were to test the hypothesis that short-term high salt intake reduces macrovascular and microvascular endothelial function in the absence of changes in blood pressure and to determine whether acute exercise restores endothelial function after high salt in women.

MATERIALS AND METHODS

Twelve women were administered high salt (11 g of sodium chloride for 7 days) and then underwent a weightlifting session. Brachial artery flow-mediated dilation and nitroglycerin dilation were measured with ultrasound at baseline, after high salt, and after weightlifting. Subcutaneous fat tissue biopsies were obtained at baseline, after high salt, and after weightlifting. Resistance arteries from biopsies were cannulated for vascular reactivity measurements in response to flow [flow-induced dilation (FID)] and acetylcholine.

RESULTS

Blood pressure was similar before and after high salt diet. Brachial flow-mediated dilation was reduced after high salt diet but was not affected by acute weightlifting. Brachial nitroglycerin dilations were similar before and after high salt. FID and acetylcholine-induced dilation of resistance arteries were similar to that of before and after high salt diet. FID and acetylcholine-induced dilation was not altered by weightlifting after high salt diet. However, N-nitro-L-arginine methyl ester significantly reduced FID at baseline and after exercise but had no effect dilator reactivity after high salt diet alone.

CONCLUSION

These data suggest that high salt intake reduces brachial artery endothelial function and switches the mediator of vasodilation in the microcirculation to a non-nitric oxide-dependent mechanism in healthy adults and acute exercise may switch the dilator mechanism back to nitric oxide during high salt diet.

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.

Low-flow mediated constriction incorporated indices as indicators of cardiovascular risk in smokers

BACKGROUND AND AIMS

Low-flow-mediated constriction (L-FMC), the endothelial response to reduced blood flow by forearm compression, is present in some smokers. The differences between smokers with and without L-FMC are unclear. It is also unknown whether flow-mediated total dilation (FMTD) or modified flow-mediated dilation (mFMD), both of which incorporate information concerning L-FMC, could be used to estimate cardiovascular risk. We sought to clarify the clinical factors associated with the presence of L-FMC in smokers according to sex and examine whether L-FMC incorporated indices would be better than a conventional index to estimate cardiovascular risk in smokers.

METHODS

In total, 140 consecutive smokers (58 ± 13 years old) with no coronary heart disease and 48 non-smokers, who comprised the age- and sex-matched control group, were enrolled.

RESULTS

L-FMC was demonstrated in 33.6% (47/140) and 25% (12/48) of the smokers and non-smokers, respectively. In male smokers, the predictors of the presence of L-FMC were age (p = 0.014), body mass index (BMI) (p = 0.045), and baseline brachial arterial diameter (Dbase) (p = 0.048). In female smokers, there were no predictors of the presence of L-FMC. The correlations between the Framingham risk score (FRS) and %FMTD (r = -0.34) and between FRS and %mFMD (r = -0.33) were stronger than that between FRS and conventional flow-mediated dilation (%cFMD) (r = -0.20).

CONCLUSIONS

Independent predictors of the presence of L-FMC were age, BMI, and Dbase in male smokers. L-FMC incorporated indices may be good alternatives to cFMD to estimate cardiovascular risk.

Association of endothelial proliferation with the magnitude of weight loss during calorie restriction

OBJECTIVES

Substantial weight loss through intense dietary regimens is thought to ameliorate endothelial dysfunction in obesity. It is less clear whether similar improvements can be achieved with modest dietary interventions. This study aimed to identify the parameters of endothelial cell status in obesity that are affected by mild calorie restriction.

METHODS

Human umbilical vein endothelial cells (EA.hy926 line) in culture were exposed pairwise to serum from 57 individuals with simple obesity (BMI > 30 kg/m(2)) collected before and after 8-week dietary intervention with energy deficit of 300-500 kcal/day.

RESULTS

Analysis of endothelial transcriptome suggested that the intervention could impact on endothelial cell growth. Cell proliferation was measured with the MTT test and verified by [(3)H]-thymidine incorporation. The participants were categorized according to a change in proliferation over time. Significant decrease in endothelial cell proliferation correlated with the extent of weight loss in men, but not in women. This effect corresponded with changes in serum levels of leptin and adiponectin, but was not related to serum concentrations of several known angiogenic mediators (VEGF, MCP-1, TSP-1, MMP-9, angiopoietin-2).

CONCLUSION

Direction and magnitude of changes in serum-induced endothelial cell proliferation identifies patients with the greatest weight loss in response to modest calorie restriction.

Endothelial dysfunction and coronary artery disease: a state of the art review

Atherosclerotic coronary artery disease (CAD) is a major cause of morbidity and mortality in the developed world. Endothelial dysfunction plays an important role in the development of atherosclerosis and predicts cardiovascular (CV) outcomes independent of conventional CV risk factors. In recent years, there have been tremendous improvements in the pharmacological prevention and management of CAD. In this review, the pathophysiology of endothelial dysfunction in relation to CAD is discussed and various techniques of invasive and noninvasive assessments of peripheral and coronary endothelial function described. In addition, evidence for the association of endothelial dysfunction and CV outcomes has been examined and finally the role of therapeutic interventions in endothelial dysfunction has been discussed.

Brachial Low-Flow-Mediated Constriction is Associated with Delayed Brachial Flow-Mediated Dilation

AIM

Flow-mediated vasodilation (FMD) of the brachial artery measures the ability of the artery to dilate after a forearm ischemia lasting for 5 min. During ischemia, and therefore in conditions of low flow, constriction of the brachial artery (L-FMC) has sometimes been reported. The meaning of L-FMC is still unclear. The aims of our study were to establish the prevalence of subjects with L-FMC, to determine whether the magnitude of L-FMC correlates with magnitude of FMD, and to determine whether L-FMC can be used to predict FMD timing.

METHODS

A total of 179 outpatients were studied, and the brachial artery diameter was measured every minute during the 5 min forearm ischemia. Subjects who had at least one measurement showing a constriction of ＞ 1% during ischemia were defined as constrictors. FMD was evaluated at 50 s, 2 min, and 3 min after cuff release. On the basis of time, the subjects in whom maximal dilation had occurred were divided into Early, Late, or No dilators.

RESULTS

The brachial artery diameter of 70 subjects (39%) constricted during ischemia. Higher the constriction during ischemia, lower was the dilation after ischemia. Constrictors were more likely to have Late (OR 2.6; ICs 95% 1.19-5.81, p=0.02) or No dilation (OR 4.8; ICs 95% 1.90-12-16, p=0.02) compared with no constrictors.

CONCLUSIONS

The present study reveals that almost 40% of the subjects had brachial artery L-FMC and a more pronounced constriction during ischemia correlated with a lower dilation after ischemia. Finally, the prevalence of subjects showing L-FMC was significantly higher among subjects with delayed or no vasodilation, suggesting that L-FMC may be a marker of endothelial dysfunction.

Presence of a high-flow-mediated constriction phenomenon prior to flow-mediated dilation in normal weight, overweight, and obese children and adolescents

PURPOSE

When assessing vasomotor endothelial function by reactive hyperemia, the brachial artery, in some individuals, constricts immediately before beginning to dilate following cuff release. We call this response high-flow-mediated constriction (H-FMC). The aim of this study was to describe the rate of the H-FMC during reactive hyperemia in children and adolescents throughout a range of body mass index (BMI) values, and to investigate differences in flow-mediated dilation (FMD), cardiovascular, and anthropometric measures between subjects with and without H-FMC.

METHODS

FMD was assessed in 136 children and adolescents (61 male, 75 female; 13 ± 3 years) by sonographic imaging of the brachial artery. H-FMC was characterized as the lowest point from the baseline brachial artery diameter immediately following reactive cuff release. Independent t tests were used to compare subjects with and without H-FMC.

RESULTS

H-FMC was observed in 91 of the 136 participants (66.9%). No significant difference was found between H-FMC and non-H-FMC subjects for age (p = 0.602), gender (p = 0.767), height (p = 0.227), or weight (p = 0.171). BMI percentile was nonsignificantly higher (91.8 ± 4.9th versus 84.6 ± 22.8th percentile, p = 0.057) and FMD was significantly lower (5.43 ± 3.41% versus 8.05 ± 3.97%, p < 0.001) in H-FMC than in non-H-FMC subjects. Adding H-FMC to FMD produced no significant difference between H-FMC and non-H-FMC individuals (8.03 ± 3.27% versus 8.05 ± 3.97%, p = 0.977).

CONCLUSIONS

Approximately 67% of participants demonstrated an H-FMC during reactive hyperemia. BMI percentile was nonsignificantly higher and FMD was significantly lower in children and adolescents who displayed this phenomenon.

Normal Pregnancy Is Associated with Changes in Central Hemodynamics and Enhanced Recruitable, but Not Resting, Endothelial Function

Introduction. Flow-mediated dilation (FMD), low flow-mediated constriction (L-FMC), and reactive hyperemia-related changes in carotid-to-radial pulse wave velocity (ΔPWVcr%) could offer complementary information about both “recruitability” and “resting” endothelial function (EF). Carotid-to-femoral pulse wave velocity (PWVcf) and pulse wave analysis-derived parameters (i.e., AIx@75) are the gold standard methods for noninvasive evaluation of aortic stiffness and central hemodynamics. If healthy pregnancy is associated with both changes in resting and recruitable EF, as well as in several arterial parameters, it remains unknown and/or controversial. Objectives. To simultaneously and noninvasively assess in healthy pregnant (HP) and nonpregnant (NP) women central parameters in conjunction with “basal and recruitable” EF, employing new complementary approaches. Methods. HP (n = 11, 34.2 ± 3.3 weeks of gestation) and age- and cardiovascular risk factors-matched NP (n = 22) were included. Aortic blood pressure (BP), AIx@75, PWVcf, common carotid stiffness, and intima-media thickness, as well as FMD, L-FMC, and ΔPWVcr %, were measured. Results. Aortic BP, stiffness, and AIx@75 were reduced in HP. ΔPWVcr% and FMD were enhanced in HP in comparison to NP. No differences were found in L-FMC between groups. Conclusion. HP is associated with reduced aortic stiffness, central BP, wave reflections, and enhanced recruitable, but not resting, EF.

Preeclampsia Is Associated with Increased Central Aortic Pressure, Elastic Arteries Stiffness and Wave Reflections, and Resting and Recruitable Endothelial Dysfunction

Introduction. An altered endothelial function (EF) could be associated with preeclampsia (PE). However, more specific and complementary analyses are required to confirm this topic. Flow-mediated dilation (FMD), low-flow-mediated constriction (L-FMC), and hyperemic-related changes in carotid-radial pulse wave velocity (PWVcr) offer complementary information about “recruitability” of EF. Objectives. To evaluate, in healthy and hypertensive pregnant women (with and without PE), central arterial parameters in conjunction with “basal and recruitable” EF. Methods. Nonhypertensive (HP) and hypertensive pregnant women (gestational hypertension, GH; preeclampsia, PE) were included. Aortic blood pressure (BP), wave reflection parameters (AIx@75), aortic pulse wave velocity (PWVcf) and PWVcr, and brachial and common carotid stiffness and intima-media thickness were measured. Brachial FMD and L-FMC and hyperemic-related change in PWVcr were measured. Results. Aortic BP and AIx@75 were elevated in PE. PE showed stiffer elastic but not muscular arteries. After cuff deflation, PWVcr decreased in HP, while GH showed a blunted PWVcr response and PE showed a tendency to increase. Maximal FMD and L-FMC were observed in HP followed by GH; PE did not reach significant arterial constriction. Conclusion. Aortic BP and wave reflections as well as elastic arteries stiffness are increased in PE. PE showed both “resting and recruitable” endothelial dysfunctions.

Effects of clopidogrel, prasugrel and ticagrelor on endothelial function, inflammatory and oxidative stress parameters and platelet function in patients undergoing coronary artery stenting for an acute coronary syndrome. A randomised, prospective, controlled study

INTRODUCTION

Particularly in the setting of acute coronary syndromes, the interplay between vascular and platelet function has been postulated to have direct clinical implications. The present trial is designed to test the effect of clopidogrel, prasugrel and ticagrelor on multiple parameters of vascular function, platelet aggregation, oxidative and inflammatory stress before and up to 4 weeks after coronary artery stenting.

METHODS AND ANALYSIS

The study is designed as a three-arm, parallel design, randomised, investigator-blinded study. Patients with unstable angina or non-ST elevation myocardial infarction undergoing coronary intervention with a drug-eluting stent will be randomised to receive 600 mg clopidogrel, 60 mg prasugrel or 180 mg ticagrelor followed by oral therapy with the same drug. The primary endpoint of the trial is the impact of antiplatelet treatments on endothelial function as assessed by flow-mediated dilation at 1 day, 1 week and 1 month in patients who have undergone stenting. Secondary endpoints include the impact of study medications on parameters of macrovascular and microvascular function, platelet reactivity, oxidative and inflammatory stress. The study recruitment is currently ongoing and, after an interim analysis which was performed at 50% of the initially planned population, it is planned to continue until July 2015.

ETHICS AND DISSEMINATION

The protocol was approved by the local ethics committee. The trial will provide important pathophysiological insight on the relationship between platelet aggregation and endothelial function, two parameters that have been shown to influence patients' prognosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT01700322; EudraCT-Nr.: 2011-005305-73. Current V.1.3, from 24 February 2014.

Low-flow mediated constriction: the yin to FMD's yang?

Given the prevalence of cardiovascular disease (CVD), early detection is crucial. Although traditional cardiovascular risk factors relate to future CVD, the predictive value of these risk factors can be relatively limited. Contemporary scientific attention has focused on alternative direct measures of arterial function. Based on the ability of the endothelium to acutely dilate in response to an increase in flow, 'flow mediated dilation' (FMD) was introduced approximately 20 years ago and is now an established non-invasive index of endothelial function predictive of future cardiovascular events. Recently, 'low-flow mediated constriction' (L-FMC) has been proposed as a complementary addition to FMD. The technique is based on the constrictor response to decreased flow and is claimed to improve the sensitivity and specificity of FMD. The aim of this review is to examine literature pertaining to this novel technique and to provide insight into the potential use of L-FMC in future research.

Recovery of flow-mediated vasodilatation after repetitive measurements is involved in early vascular impairment: comparison with indices of vascular tone

In repetitive measurements of flow-mediated dilatation (FMD), the duration of the interval between measurements remains controversial. In this pilot study, we conducted three sequential measurements of low-flow-mediated constriction (L-FMC), FMD and flow-mediated total dilation (FMTD; L-FMC+ FMD) at baseline and intervals of 15 and 60 min in 30 healthy males. FMD15, L-FMC15, and FMTD15 were significantly lower than the respective first measurements, but all indices showed full recovery at 60 min in all subjects. The baseline diameter was slightly increased at 15 min and restored at 60 min, but the maximum diameter, and the baseline and reactive flow velocity unchanged. We examined the relationship between recovery rate of FMTD at 15 min (FMTD-R) and cardio-ankle vascular index (CAVI). Univariate analysis showed moderate correlation between FMTD-R, and CAVI and L-FMC0. Patients were divided according to FMTD-R value; the low-FMTD-R group [below the median value (-26.2%)] included a significantly higher proportion of smokers and higher CAVI values than the high-FMTD-R group. The reproducibility of FMTD and FMTD-R was evaluated in another group of 25 healthy subjects. The range of variation across measurements was 1.1% for FMTD and 4.6% for FMTD-R; with intraclass correlation coefficients of 0.93 and 0.95, respectively. The present study demonstrated blunted recovery of FMD within 15 min, suggesting the need for selection of a more adequate interval between measurements to avoid underestimation of FMD in subsequent measurements. The findings demonstrated the reproducibility of FMTD-R and FMTD measurements, and that FMTD-R might be involved in arterial stiffness and early vascular impairment in the healthy subjects.

Effect of head-out water immersion on vascular function in healthy subjects

Immersion in thermoneutral water increases cardiac output and peripheral blood flow and reduces systemic vascular resistance. This study examined the effects of head-out water immersion on vascular function. Twelve healthy middle-aged males were immersed during 60 min in the seated position, with water at the level of xiphoid. Local and central vascular tone regulating systems were studied during that time. Brachial artery diameter and blood flow were recorded using ultrasonography and Doppler. Endothelial function was assessed with flow-mediated dilation. Results were compared with the same investigations performed under reference conditions in ambient air. During water immersion, brachial artery diameter increased (3.7 ± 0.2 mm in ambient air vs. 4 ± 0.2 mm in water immersion; p < 0.05). Endothelium-mediated dilation was significantly lower in water immersion than in ambient air (10% vs. 15%; p = 0.01). Nevertheless, the difference disappeared when the percentage vasodilatation of the brachial artery was normalized to the shear stimulus. Smooth muscle-mediated dilation was similar in the 2 conditions. Spectral analysis of systolic blood pressure variability indicated a decrease in sympathetic vascular activity. Plasma levels of nitric oxide metabolites remained unchanged, whereas levels of natriuretic peptides were significantly elevated. An increase in brachial blood flow, a decrease in sympathetic activity, a warming of the skin, and an increase in natriuretic peptides might be involved in the increase in reference diameter observed during water immersion. Endothelial cell reactivity and smooth muscle function did not appear to be altered.

Brachial artery constriction during brachial artery reactivity testing predicts major adverse clinical outcomes in women with suspected myocardial ischemia: results from the NHLBI-sponsored women's ischemia Syndrome Evaluation (WISE) Study

BACKGROUND

Limited brachial artery (BA) flow-mediated dilation during brachial artery reactivity testing (BART) has been linked to increased cardiovascular risk. We report on the phenomenon of BA constriction (BAC) following hyperemia.

OBJECTIVES

To determine whether BAC predicts adverse CV outcomes and/or mortality in the women's ischemic Syndrome Evaluation Study (WISE). Further, as a secondary objective we sought to determine the risk factors associated with BAC.

METHODS

We performed BART on 377 women with chest pain referred for coronary angiography and followed for a median of 9.5 years. Forearm ischemia was induced with 4 minutes occlusion by a cuff placed distal to the BA and inflated to 40mm Hg > systolic pressure. BAC was defined as >4.8% artery constriction following release of the cuff. The main outcome was major adverse events (MACE) including all-cause mortality, non-fatal MI, non-fatal stroke, or hospitalization for heart failure.

RESULTS

BA diameter change ranged from -20.6% to +44.9%, and 41 (11%) women experienced BAC. Obstructive CAD and traditional CAD risk factors were not predictive of BAC. Overall, 39% of women with BAC experienced MACE vs. 22% without BAC (p=0.004). In multivariate Cox proportional hazards regression, BAC was a significant independent predictor of MACE (p=0.018) when adjusting for obstructive CAD and traditional risk factors.

CONCLUSIONS

BAC predicts almost double the risk for major adverse events compared to patients without BAC. This risk was not accounted for by CAD or traditional risk factors. The novel risk marker of BAC requires further investigation in women.