Reactive hyperemia is associated with adverse clinical outcomes in heart failure

Sitting leg vasculopathy: potential adaptations beyond the endothelium

Increased sitting time, the most common form of sedentary behavior, is an independent risk factor for all-cause and cardiovascular disease mortality; however, the mechanisms linking sitting to cardiovascular risk remain largely elusive. Studies over the last decade have led to the concept that excessive time spent in the sitting position and the ensuing reduction in leg blood flow-induced shear stress cause endothelial dysfunction. This conclusion has been mainly supported by studies using flow-mediated dilation in the lower extremities as the measured outcome. In this review, we summarize evidence from classic studies and more recent ones that collectively support the notion that prolonged sitting-induced leg vascular dysfunction is likely also attributable to changes occurring in vascular smooth muscle cells (VSMCs). Indeed, we provide evidence that prolonged constriction of resistance arteries can lead to modifications in the structural characteristics of the vascular wall, including polymerization of actin filaments in VSMCs and inward remodeling, and that these changes manifest in a time frame that is consistent with the vascular changes observed with prolonged sitting. We expect this review will stimulate future studies with a focus on VSMC cytoskeletal remodeling as a potential target to prevent the detrimental vascular ramifications of too much sitting.

Association between Fractional Oxygen Extraction from Resting Quadriceps Muscle and Body Composition in Healthy Men

This study aimed to associate body composition with fractional oxygen extraction at rest in healthy adult men. Fourteen healthy adults (26.93 ± 2.49 years) from Chile participated. Body composition was assessed with octopole bioimpedance, and resting muscle oxygenation was evaluated in the vastus lateralis quadriceps with near-infrared spectroscopy (NIRS) during a vascular occlusion test, analyzing the muscleVO2, resaturation velocity during reactive hyperemia via the muscle saturation index (%TSI), and the area above the curve of HHb (AACrep). It was observed that the total and segmented fat mass are associated with lower reoxygenation velocities during hyperemia (p = 0.008; β = 0.678: p = 0.002; β = 0.751), and that the total and segmented skeletal muscle mass are associated with higher reoxygenation velocities during hyperemia (p = 0.020; β = -0.614: p = 0.027; β = -0.587). It was also observed that the total and segmented fat mass were associated with a higher area above the curve of HHb (AACrep) during hyperemia (p = 0.007; β = 0.692: p = 0.037; β = 0.564), and that total and segmented skeletal muscle mass was associated with a lower area above the curve of HHb (AACrep) during hyperemia (p = 0.007; β = -0.703: p = 0.017; β = -0.632). We concluded that fat mass is associated with lower resaturation rates and lower resting fractional O2 extraction levels. In contrast, skeletal muscle mass is associated with higher resaturation rates and fractional O2 extraction during reactive hyperemia. The AACrep may be relevant in the evaluation of vascular adaptations to exercise and metabolic health.

Evaluation of inter-rater and test-retest reliability for near-infrared spectroscopy reactive hyperemia measures

BACKGROUND

Near-infrared spectroscopy (NIRS) is a non-invasive tool used to measure blood flow in peripheral tissues. More information on inter-rater agreement and test-retest reliability of NIRS-based reperfusion assessments is needed.

PURPOSE

To assess inter-rater agreement for NIRS based data analysis, and evaluate the measurement's reliability across days.

METHODS

On three separate days (average days between visits 1 and 3: 19.4 ± 6.9 days), participants' (N = 15 males, 22 ± 2 yr.) post-occlusion reactive hyperemia (PORH) was measured in the left gastrocnemius muscle using Continuous-Wave NIRS (CW-NIRS). A blood pressure cuff was placed proximal to the knee and inflated to occlude lower leg blood flow for 5 min. The following CW-NIRS parameters were selected: (1) percent saturation in HbO₂ (StO₂%) at baseline; (2) the O₂Hb range used to normalize the NIRS signal; (3) the time for the O₂Hb signal to reach 50 % peak post-occlusion hyperemia (T_1/2), and (4) the post peak hyperemic O₂Hb recovery slope (O₂REC-SLP). Absolute agreement between the two analysts was calculated using two-way random effects Intraclass Correlation Coefficients (ICC_2,1). Consistency between analysts and across days was calculated using two-way mixed models (ICC_3,1). Mean and 95 % confidence intervals (CI) of ICCs are reported. Coefficient of variation (CV) and standard error of the measurement (SEM) are reported.

RESULTS

The ICC_2,1 data indicated "adequate" to "excellent" absolute agreement between the two NIRS analysts. ICC_2,3 data indicated "adequate" to "good" reliability across visits. The CV and SEM for rater 1 and rater 2 across visit were StO₂ (CV: 3.79 % ± 2.71 % and 4.50 % ± 2.37 %; SEM: 3.42 and 3.82), O₂Hb range (CV: 10.50 ± 5.93 and 12.79 ± 12.41; SEM: 3.26 and 4.71), T_1/2 (CV: 11.15 % ± 5.52 % and 10.96 % ± 4.50; SEM: 1.22 and 1.11), and O₂REC-SLP (CV: 19.49 % ± 9.99 % and 18.45 % ± 9.48 %; SEM: 0.04 and 0.04).

CONCLUSION

It is concluded that NIRS parameters assessed show adequate reliability between analysts and across three visits. It is recommended, when feasible and because of the absence of 100 % reliability, that investigators employ more than one rater for scoring at least a portion of the data across each trial in a study's control condition in order to have the ability to estimate the magnitude of error attributable to imperfect reliability.

Maximal calf conductance is associated with 6-minute walk distance in participants with and without peripheral artery disease

INTRODUCTION

The aims were (a) to compare the maximal calf conductance and 6-minute walk distance of participants with and without peripheral artery disease (PAD) and claudication, (b) to determine whether maximal calf conductance was more strongly associated with 6-minute walk distance in participants with PAD than in the controls, and (c) to determine whether this association was significant in participants with PAD after adjusting for ABI, as well as for demographic, anthropometric, and comorbid variables.

METHODS

Participants with PAD (n = 633) and without PAD (n = 327) were assessed on maximal calf conductance using venous occlusion plethysmography, and on 6-minute walk distance. Participants were further characterized on ABI, and on demographic, anthropometric, and comorbid variables.

RESULTS

The PAD group had lower maximal calf conductance than the control group (0.136 ± 0.071 vs 0.201 ± 0.113 mL/100 mL/min/mmHg, p < 0.001). Additionally, the PAD group had a lower 6-minute walk distance (375 ± 98 m vs 480 ± 107 m, p < 0.001). Maximal calf conductance was positively associated with 6-minute walk distance in both groups (p < 0.001) and was more strongly associated in the PAD group (p < 0.001). In adjusted analyses, maximal calf conductance remained positively associated with 6-minute walk distance in the PAD group (p < 0.001) and in the control group (p < 0.001).

CONCLUSIONS

Participants with PAD and claudication had impaired maximal calf conductance and a lower 6-minute walk distance than those without PAD, and maximal calf conductance was positively and independently associated with 6-minute walk distance within each group before and after adjusting for ABI, and for demographic, anthropometric, and comorbid variables.

Prognostic value of reactive hyperemia index using peripheral artery tonometry in patients with heart failure

Given the high prevalence and poor prognosis of heart failure (HF), finding prognostic factors for patients with HF is crucial. This study investigated the prognostic value of reactive hyperemia index (RHI), a measure of endothelial function, in HF. A total of 90 HF patients (mean age, 63.7 ± 13.2 years; female, 25.6%) with a history of hospitalization for HF treatment were prospectively enrolled. RHI was measured using digital arterial tonometry in a stable condition. Clinical events, including all-cause death and HF admission, were assessed. During the median follow-up of 3.66 years (interquartile range, 0.91-4.94 years), 26 clinical events (28.9%) occurred. Although there were no significant differences in risk factors and laboratory findings according to the occurrence of clinical events, the RHI value was significantly lower in patients with clinical events than in those without (1.21 ± 0.34 vs. 1.68 ± 0.48; P < 0.001). Kaplan-Meier survival analysis showed that a lower RHI value (< 1.48) was associated with a significantly higher incidence rate of clinical events (log-rank P < 0.001). In multivariable cox regression analysis, a low RHI value (< 1.48) was associated with an increased risk of clinical events (hazard ratio, 14.09; 95% confidence interval, 3.61-54.99; P < 0.001) even after controlling for potential confounders. Our study showed that reduced RHI was associated with an increased risk of adverse clinical outcomes in HF. This suggests that endothelial dysfunction may be an important prognostic marker in patients with HF.

Metabolic and microvascular function assessed using near-infrared spectroscopy with vascular occlusion in women: age differences and reliability

NEW FINDINGS

What is the central question of this study? Can the near-infrared spectroscopy with vascular occlusion test (NIRS-VOT) reliably measure skeletal muscle metabolic and microvascular function in women? What is the main finding and its importance? The NIRS-VOT can be used as a reliable technique for the assessment of skeletal muscle metabolism and microvascular function in women, with reliability being generally greater in younger women. These findings have important implications for the planning and development of future studies employing the NIRS-VOT in women, and provide insights into the effects of age on these parameters in women specifically.

ABSTRACT

We investigated the test-retest reliability of, and age-related differences in, markers of skeletal muscle metabolism and microvascular function derived from the near-infrared spectroscopy with vascular occlusion test (NIRS-VOT) in younger women (YW) and middle-aged and older women (MAOW). Seventeen YW (age 23 ± 4 years) and 17 MAOW (age 59 ± 8 years) completed this study. Participants completed identical experimental visits separated by ∼4 weeks during which the NIRS-VOT was used to quantify the occlusion slope, minimum and maximum tissue saturation, ischaemic index, reperfusion magnitude, the reperfusion and 10-s reperfusion slopes (slope 2 and slope 210-s ), time to max tissue saturation, and area under the reperfusion curve using the local tissue oxygen saturation signal. Except for slope 210-s (intraclass correlation coefficient (ICC) = 0.37; coefficient of variation (CV) = 31%), time to max tissue saturation (ICC = 0.21), and ischaemic index (ICC = 0.37) for MAOW, all of the NIRS variables demonstrated good to excellent relative reliability for the YW (ICCs = 0.74-0.86) and the MAOW (ICCs = 0.51-0.87), with CVs of 2-21% and 2-22%, respectively. The occlusion slope was significantly lower, indicating accelerated deoxygenation, while maximum tissue saturation, reperfusion magnitude, and ischaemic index were significantly higher in YW versus MAOW. No other group differences were found. In conclusion, our data support the use of the NIRS-VOT as a simple, reliable, non-invasive technique for the assessment of peripheral skeletal muscle metabolism and microvascular function in women, with the reliability being generally greater in YW versus MAOW. Further, our data suggest that ageing is associated with lower skeletal muscle metabolism and microvascular hyperaemic responsiveness in women.

Crosstalk between adenosine receptors and CYP450-derived oxylipins in the modulation of cardiovascular, including coronary reactive hyperemic response

Adenosine is a ubiquitous endogenous nucleoside or autacoid that affects the cardiovascular system through the activation of four G-protein coupled receptors: adenosine A₁ receptor (A₁AR), adenosine A_2A receptor (A_2AAR), adenosine A_2B receptor (A_2BAR), and adenosine A₃ receptor (A₃AR). With the rapid generation of this nucleoside from cellular metabolism and the widespread distribution of its four G-protein coupled receptors in almost all organs and tissues of the body, this autacoid induces multiple physiological as well as pathological effects, not only regulating the cardiovascular system but also the central nervous system, peripheral vascular system, and immune system. Mounting evidence shows the role of CYP450-enzymes in cardiovascular physiology and pathology, and the genetic polymorphisms in CYP450s can increase susceptibility to cardiovascular diseases (CVDs). One of the most important physiological roles of CYP450-epoxygenases (CYP450-2C & CYP2J2) is the metabolism of arachidonic acid (AA) and linoleic acid (LA) into epoxyeicosatrienoic acids (EETs) and epoxyoctadecaenoic acid (EpOMEs) which generally involve in vasodilation. Like an increase in coronary reactive hyperemia (CRH), an increase in anti-inflammation, and cardioprotective effects. Moreover, the genetic polymorphisms in CYP450-epoxygenases will change the beneficial cardiovascular effects of metabolites or oxylipins into detrimental effects. The soluble epoxide hydrolase (sEH) is another crucial enzyme ubiquitously expressed in all living organisms and almost all organs and tissues. However, in contrast to CYP450-epoxygenases, sEH converts EETs into dihydroxyeicosatrienoic acid (DHETs), EpOMEs into dihydroxyoctadecaenoic acid (DiHOMEs), and others and reverses the beneficial effects of epoxy-fatty acids leading to vasoconstriction, reducing CRH, increase in pro-inflammation, increase in pro-thrombotic and become less cardioprotective. Therefore, polymorphisms in the sEH gene (Ephx2) cause the enzyme to become overactive, making it more vulnerable to CVDs, including hypertension. Besides the sEH, ω-hydroxylases (CYP450-4A11 & CYP450-4F2) derived metabolites from AA, ω terminal-hydroxyeicosatetraenoic acids (19-, 20-HETE), lipoxygenase-derived mid-chain hydroxyeicosatetraenoic acids (5-, 11-, 12-, 15-HETEs), and the cyclooxygenase-derived prostanoids (prostaglandins: PGD₂, PGF_2α; thromboxane: Txs, oxylipins) are involved in vasoconstriction, hypertension, reduction in CRH, pro-inflammation and cardiac toxicity. Interestingly, the interactions of adenosine receptors (A_2AAR, A₁AR) with CYP450-epoxygenases, ω-hydroxylases, sEH, and their derived metabolites or oxygenated polyunsaturated fatty acids (PUFAs or oxylipins) is shown in the regulation of the cardiovascular functions. In addition, much evidence demonstrates polymorphisms in CYP450-epoxygenases, ω-hydroxylases, and sEH genes (Ephx2) and adenosine receptor genes (ADORA1 & ADORA2) in the human population with the susceptibility to CVDs, including hypertension. CVDs are the number one cause of death globally, coronary artery disease (CAD) was the leading cause of death in the US in 2019, and hypertension is one of the most potent causes of CVDs. This review summarizes the articles related to the crosstalk between adenosine receptors and CYP450-derived oxylipins in vascular, including the CRH response in regular salt-diet fed and high salt-diet fed mice with the correlation of heart perfusate/plasma oxylipins. By using A_2AAR^-/-, A₁AR^-/-, eNOS^-/-, sEH^-/- or Ephx2^-/-, vascular sEH-overexpressed (Tie2-sEH Tr), vascular CYP2J2-overexpressed (Tie2-CYP2J2 Tr), and wild-type (WT) mice. This review article also summarizes the role of pro-and anti-inflammatory oxylipins in cardiovascular function/dysfunction in mice and humans. Therefore, more studies are needed better to understand the crosstalk between the adenosine receptors and eicosanoids to develop diagnostic and therapeutic tools by using plasma oxylipins profiles in CVDs, including hypertensive cases in the future.

Optoacoustic Imaging Offers New Insights into In Vivo Human Skin Vascular Physiology

Functional imaging with new photoacoustic tomography (PAT) offers improved spatial and temporal resolution quality in in vivo human skin vascular assessments. In the present study, we followed a suprasystolic reactive hyperemia (RH) maneuver with a multi-spectral optoacoustic tomography (MSOT) system. A convenience sample of ten participants, both sexes, mean age of 35.8 ± 13.3 years old, was selected. All procedures were in accordance with the principles of good clinical practice and approved by the institutional ethics committee. Images were obtained at baseline (resting), during occlusion, and immediately after pressure release. Observations of the RH by PAT identified superficial and deeper vascular structures parallel to the skin surface as part of the human skin vascular plexus. Furthermore, PAT revealed that the suprasystolic occlusion impacts both plexus differently, practically obliterating the superficial smaller vessels and evoking stasis at the deeper, larger structures in real-time (live) conditions. This dual effect of RH on the skin plexus has not been explored and is not considered in clinical settings. Thus, RH seems to represent much more than the local microvascular reperfusion as typically described, and PAT offers a vast potential for vascular clinical and preclinical research.

Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies

The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.

Lifestyle modification and cognitive function among individuals with resistant hypertension: cognitive outcomes from the TRIUMPH trial

BACKGROUND

Resistant hypertension is associated with increased risk of cognitive decline, stroke, and dementia. Lifestyle modification has been suggested to improve cognitive function through its salutary effects on vascular function.

METHODS

Participants included 140 patients with resistant hypertension participating in the TRIUMPH trial. Participants were randomized to a cardiac rehabilitation-based lifestyle program (C-LIFE) or a standardized education and physician advice condition (SEPA). Participants completed a 45-min cognitive test battery consisting of tests of Executive Functioning and Learning, Memory, and Processing Speed. Biomarkers of vascular [flow mediated dilation of the brachial artery (FMD)], microvascular, and cerebrovascular function were also collected, in addition to weight, fitness, and ambulatory blood pressure.

RESULTS

Participants averaged 63 years of age, 48% women, 59% black, and obese [mean BMI = 36 kg/m 2 (SD = 4)]. Cognitive performance improved across the entire cohort during the 4-month trial [ t -scores pretreatment = 48.9 (48, 50) vs. posttreatment = 50.0 (49, 51), P  < 0.001]. Postintervention Executive Function/Learning composite performance was higher for participants in C-LIFE compared to SEPA ( d  = 0.37, P  = 0.039). C-LIFE intervention effects on Memory and Processing Speed were moderated by sex and baseline stroke risk, respectively ( P  = 0.026 and P  = 0.043 for interactions), such that males and participants with greater stroke risk showed the greatest cognitive changes. FMD [C-LIFE: +0.3% (-0.3, 1.0) vs. SEPA: -1.4% (-2.5, -0.3), P  = 0.022], and microvascular function [C-LIFE: 97 (65, 130) vs. SEPA: 025 (-75, 23), P  < 0.001] were improved in C-LIFE compared with SEPA, whereas cerebrovascular reactivity was not [C-LIFE: -0.2 (-0.4, 0) vs. SEPA: 0.1 (-0.2, 0.4), P  = 0.197). Mediation analyses suggested that increased executive function/learning was associated with reduced ambulatory SBP levels secondary to weight loss [indirect effect: B  = 0.25 (0.03, 0.71)].

CONCLUSION

Lifestyle modification individuals with resistant hypertension improves cognition, which appeared to be associated with reduced ambulatory SBP changes through weight loss. Cognitive improvements were accompanied by parallel improvements in endothelial and microvascular function.

Cerebrovascular Function, Vascular Risk, and Lifestyle Patterns in Resistant Hypertension

BACKGROUND

Impaired cerebrovascular reactivity (CVR) and blunted cerebral hemodynamic recruitment are thought to be important mechanisms linking hypertension to cerebrovascular and cognitive outcomes. Few studies have examined cardiovascular or dietary correlates of CVR among hypertensives.

OBJECTIVE

To delineate associations between cardiometabolic risk, diet, and cerebrovascular functioning among individuals with resistant hypertension from the TRIUMPH trial (n = 140).

METHODS

CVR was assessed by examining changes in tissue oxygenation (tissue oxygenation index [TOI] and oxygenated hemoglobin [HBO2]) using functional near-infrared spectroscopy (fNIRS) during a breath holding test, a standardized CVR assessment to elicit a hypercapnic response. Participants also underwent fNIRS during three cognitive challenge tasks. Vascular function was assessed by measurement of brachial artery flow mediated dilation and hyperemic flow response. Cardiometabolic fitness was assessed from peak VO2 on an exercise treadmill test and body mass index. Dietary patterns were quantified using the DASH eating score. Cognitive function was assessed using a 45-minute test battery assessing Executive Function, Processing Speed, and Memory.

RESULTS

Greater levels fitness (B = 0.30, p = 0.011), DASH compliance (B = 0.19, p = 0.045), and lower obesity (B = -0.30, p = 0.004), associated with greater changes in TOI, whereas greater flow-mediated dilation (B = 0.19, p = 0.031) and lower stroke risk (B = -0.19, p = 0.049) associated with greater HBO2. Similar associations were found for cerebral hemodynamic recruitment, and associations between CVR and cognition were moderated by duration of hypertension.

CONCLUSION

Impaired CVR elevated cardiometabolic risk, obesity, vascular function, and fitness among hypertensives.

Post-occlusive reactive hyperemia and skeletal muscle capillary hemodynamics

Post-occlusive reactive hyperemia (PORH) is an accepted diagnostic tool for assessing peripheral macrovascular function. While conduit artery hemodynamics have been well defined, the impact of PORH on capillary hemodynamics remains unknown, despite the microvasculature being the dominant site of vascular control. Therefore, the purpose of this investigation was to determine the effects of 5 min of feed artery occlusion on capillary hemodynamics in skeletal muscle. We tested the hypothesis that, upon release of arterial occlusion, there would be: 1) an increased red blood cell flux (fRBC) and red blood cell velocity (VRBC), and 2) a decreased proportion of capillaries supporting RBC flow compared to the pre-occlusion condition.

METHODS

In female Sprague-Dawley rats (n = 6), the spinotrapezius muscle was exteriorized for evaluation of capillary hemodynamics pre-occlusion, 5 min of feed artery occlusion (Occ), and 5 min of reperfusion (Post-Occ).

RESULTS

There were no differences in mean arterial pressure (MAP) or capillary diameter (Dc) between pre-occlusion and post-occlusion (P > 0.05). During 30 s of PORH, capillary fRBC was increased (pre: 59 ± 4 vs. 30 s-post: 77 ± 2 cells/s; P < 0.05) and VRBC was not changed (pre: 300 ± 24 vs. 30 s post: 322 ± 25 μm/s; P > 0.05). Capillary hematocrit (Hctcap) was unchanged across the pre- to post-occlusion conditions (P > 0.05). Following occlusion, there was a 20-30% decrease in the number of capillaries supporting RBC flow at 30 s and 300 s-post occlusion (pre: 92 ± 2%; 30 s-post: 66 ± 3%; 300 s-post: 72 ± 6%; both P < 0.05).

CONCLUSION

Short-term feed artery occlusion (i.e. 5 min) resulted in a more heterogeneous capillary flow profile with the presence of capillary no-reflow, decreasing the percentage of capillaries supporting RBC flow. A complex interaction between myogenic and metabolic mechanisms at the arteriolar level may play a role in the capillary no-reflow with PORH. Measurements at the level of the conduit artery mask significant alterations in blood flow distribution in the microcirculation.

Assessing the impact of aging and blood pressure on dermal microvasculature by reactive hyperemia optical coherence tomography angiography

Visualization and quantification of the skin microvasculature are important for studying the health of the human microcirculation. We correlated structural and pathophysiological changes of the dermal capillary-level microvasculature with age and blood pressure by using the reactive hyperemia optical coherence tomography angiography (RH-OCT-A) technique and evaluated both conventional OCT-A and the RH-OCT-A method as non-invasive imaging alternatives to histopathology. This observational pilot study acquired OCT-A and RH-OCT-A images of the dermal microvasculature of 13 young and 12 old healthy Caucasian female subjects. Two skin biopsies were collected per subject for histological analysis. The dermal microvasculature in OCT-A, RH-OCT-A, and histological images were automatically quantified and significant indications of vessel rarefaction in both old subjects and subjects with high blood pressure were observed by RH-OCT-A and histopathology. We showed that an increase in dermal microvasculature perfusion in response to reactive hyperemia was significantly lower in high blood pressure subjects compared to normal blood pressure subjects (117% vs. 229%). These results demonstrate that RH-OCT-A imaging holds functional information of the microvasculature with respect to physiological factors such as age and blood pressure that may help to monitor early disease progression and assess overall vascular health. Additionally, our results suggest that RH-OCT-A images may serve as a non-invasive alternative to histopathology for vascular analysis.

Impaired Peripheral Microvascular Function and Risk of Major Adverse Cardiovascular Events in Patients With Coronary Artery Disease

[Figure: see text].

Sacubitril-valsartan improves conduit vessel function and functional capacity and reduces inflammation in heart failure with reduced ejection fraction

The Prospective comparison of ARNI with angiotensin-converting enzyme inhibitor to Determine Impact on Global Mortality and morbidity in Heart Failure trial identified a marked reduction in the risk of death and hospitalization for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) treated with sacubitril-valsartan (trade name Entresto), but the physiological processes underpinning these improvements are unclear. We tested the hypothesis that treatment with sacubitril-valsartan improves peripheral vascular function, functional capacity, and inflammation in patients with HFrEF. We prospectively studied patients with HFrEF (n = 11, 10 M/1 F, left ventricular ejection fraction = 27 ± 8%) on optimal, guideline-directed medical treatment who were subsequently prescribed sacubitril-valsartan (open-label, uncontrolled, and unblinded). Peripheral vascular function [brachial artery flow-mediated dilation (FMD, conduit vessel function) and reactive hyperemia (RH, microvascular function)], functional capacity [six-minute walk test (6MWT) distance], and the proinflammatory biomarkers tumor necrosis factor-α (TNF-α) and interleukin-18 (IL-18) were obtained at baseline and at 1, 2, and 3 mo of treatment. %FMD improved after 1 mo of treatment, and this favorable response persisted for months 2 and 3 (baseline: 3.25 ± 1.75%; 1 mo: 5.23 ± 2.36%; 2 mo: 5.81 ± 1.79%; 3 mo: 6.35 ± 2.77%), whereas RH remained unchanged. 6MWT distance increased at months 2 and 3 (baseline: 420 ± 92 m; 1 mo: 436 ± 98 m; 2 mo: 465 ± 115 m; 3 mo: 460 ± 110 m), and there was a sustained reduction in TNF-α (baseline: 2.38 ± 1.35 pg/mL; 1 mo: 2.06 ± 1.52 pg/mL; 2 mo: 1.95 ± 1.34 pg/mL; 3 mo: 1.92 ± 1.37 pg/mL) and a reduction in IL-18 at month 3 (baseline: 654 ± 150 pg/mL; 1 mo: 595 ± 140 pg/mL; 2 mo: 601 ± 176 pg/mL; 3 mo: 571 ± 127 pg/mL). This study provides new evidence for the potential of this new drug class to improve conduit vessel function, functional capacity, and inflammation in patients with HFrEF.NEW & NOTEWORTHY We observed an approximately twofold improvement in conduit vessel function (brachial artery FMD), increased functional capacity (6MWT distance), and a reduction in inflammation (TNF-α and IL-18) following 3 mo of sacubitril-valsartan therapy. These findings provide important new information concerning the physiological mechanisms by which this new drug class provokes favorable changes in HFrEF pathophysiology.

Resting Heart Rate as an Important Predictor of Mortality and Morbidity in Ambulatory Patients With Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND

Resting heart rate is a risk factor of adverse heart failure outcomes; however, studies have shown controversial results. This meta-analysis evaluates the association of resting heart rate with mortality and hospitalization and identifies factors influencing its effect.

METHODS AND RESULTS

We systematically searched electronic databases in February 2019 for studies published in 2005 or before that evaluated the resting heart rate as a primary predictor or covariate of multivariable models of mortality and/or hospitalization in adult ambulatory patients with heart failure. Random effects inverse variance meta-analyses were performed to calculate pooled hazard ratios. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to assess evidence quality. Sixty-two studies on 163,445 patients proved eligible. Median population heart rate was 74 bpm (interquartile range 72-76 bpm). A 10-bpm increase was significantly associated with increased risk of all-cause mortality (hazard ratio 1.10, 95% confidence interval 1.08-1.13, high quality). Overall, subgroup analyses related to patient characteristics showed no changes to the effect estimate; however, there was a strongly positive interaction with age showing increasing risk of all-cause mortality per 10 bpm increase in heart rate.

CONCLUSIONS

High-quality evidence demonstrates increasing resting heart rate is a significant predictor of all-cause mortality in ambulatory patients with heart failure on optimal medical therapy, with consistent effect across most patient factors and an increased risk trending with older age.

Kinetic differences between macro- and microvascular measures of reactive hyperemia

Postischemia reperfusion kinetics are markedly dissociated when comparing the macro- versus microvasculature. We used Doppler ultrasound and near-infrared diffuse correlation spectroscopy (NIR-DCS), an emerging technique for continuously and noninvasively quantifying relative changes in skeletal muscle microvascular perfusion (i.e., blood flow index or BFI), to measure macro- and microvascular reactive hyperemia (RH) in the nondominant arm of 16 healthy young adults. First, we manipulated the duration of limb ischemia (3 vs. 6 min) with the limb at heart level (neutral, -N). Then, we reduced/increased forearm perfusion pressure (PP) by positioning the arm above (3 min-A, 60°) or below (3 min-B, 30°) the heart. The major novel findings were twofold: first, changes in the ischemic stimulus similarly affected peak macrovascular (i.e., conduit, mL/min) and microvascular (i.e., peak NIR-DCS-derived BFI) reperfusion during reactive hyperemia (6 min-N > 3 min-N, P < 0.05, both) but did not affect the rate at which microvascular reperfusion occurs (i.e., BFI slope). Second, changing forearm PP predictably affected both peak macro- and microvascular reperfusion during RH (3 min-B > N > A, P < 0.05, all), as well as the rate at which microvascular reperfusion occurred (BFI slope; 3 min-B >N > A, P < 0.05). Together, the data suggest that kinetic differences between macro- and microvascular reperfusion are largely determined by differences in fluid mechanical energy (i.e., pressure, gravitational, and kinetic energies) between the two compartments that work in tandem to restore pressure across the arterial tree following a period of tissue ischemia.NEW & NOTEWORTHY We extend our understanding of macro- versus microvascular hemodynamics in humans, by using near-infrared diffuse correlation spectroscopy (micro-) and Doppler ultrasound (macro-) to characterize reperfusion hemodynamics following experimental manipulation of the ischemic stimulus and tissue perfusion pressure. Our results suggest kinetic differences between macro- and microvascular reperfusion are largely determined by differences in fluid mechanical energy (i.e., pressure, gravitational, and kinetic energies) between the two compartments, rather than inherent differences between the macro- and microvasculature.

TRAF3IP2 (TRAF3 Interacting Protein 2) Mediates Obesity-Associated Vascular Insulin Resistance and Dysfunction in Male Mice

Insulin resistance in the vasculature is a characteristic feature of obesity and contributes to the pathogenesis of vascular dysfunction and disease. However, the molecular mechanisms underlying obesity-associated vascular insulin resistance and dysfunction remain poorly understood. We hypothesized that TRAF3IP2 (TRAF3 interacting protein 2), a proinflammatory adaptor molecule known to activate pathological stress pathways and implicated in cardiovascular diseases, plays a causal role in obesity-associated vascular insulin resistance and dysfunction. We tested this hypothesis by employing genetic-manipulation in endothelial cells in vitro, in isolated arteries ex vivo, and diet-induced obesity in a mouse model of TRAF3IP2 ablation in vivo. We show that ectopic expression of TRAF3IP2 blunts insulin signaling in endothelial cells and diminishes endothelium-dependent vasorelaxation in isolated aortic rings. Further, 16 weeks of high fat/high sucrose feeding impaired glucose tolerance, aortic insulin-induced vasorelaxation, and hindlimb postocclusive reactive hyperemia, while increasing blood pressure and arterial stiffness in wild-type male mice. Notably, TRAF3IP2 ablation protected mice from such high fat/high sucrose feeding-induced metabolic and vascular defects. Interestingly, wild-type female mice expressed markedly reduced levels of TRAF3IP2 mRNA independent of diet and were protected against high fat/high sucrose diet-induced vascular dysfunction. These data indicate that TRAF3IP2 plays a causal role in vascular insulin resistance and dysfunction. Specifically, the present findings highlight a sexual dimorphic role of TRAF3IP2 in vascular control and identify it as a promising therapeutic target in vasculometabolic derangements associated with obesity, particularly in males.

Differential effects of tobacco cigarettes and electronic cigarettes on endothelial function in healthy young people

Tobacco cigarette (TC) smoking has never been lower in the United States, but electronic cigarette (EC) vaping has reached epidemic proportions among our youth. Endothelial dysfunction, as measured by flow-mediated vasodilation (FMD) is a predictor of future atherosclerosis and adverse cardiovascular events and is impaired in young TC smokers, but whether FMD is also reduced in young EC vapers is uncertain. The aim of this study in otherwise healthy young people was to compare the effects of acute and chronic tobacco cigarette (TC) smoking and electronic cigarette (EC) vaping on FMD. FMD was compared in 47 nonsmokers (NS), 49 chronic EC vapers, and 40 chronic TC smokers at baseline and then after EC vapers (n = 31) and nonsmokers (n = 47) acutely used an EC with nicotine (ECN), EC without nicotine (EC0), and nicotine inhaler (NI) at ~4-wk intervals and after TC smokers (n = 33) acutely smoked a TC, compared with sham control. Mean age (NS, 26.3 ± 5.2 vs. EC, 27.4 ± 5.45 vs. TC, 27.1 ± 5.51 yr, P = 0.53) was similar among the groups, but there were more female nonsmokers. Baseline FMD was not different among the groups (NS, 7.7 ± 4.5 vs. EC:6.6 ± 3.6 vs. TC, 7.9 ± 3.7%∆, P = 0.35), even when compared by group and sex. Acute TC smoking versus control impaired FMD (FMD pre-/postsmoking, -2.52 ± 0.92 vs. 0.65 ± 0.93%∆, P = 0.02). Although the increase in plasma nicotine was similar after EC vapers used the ECN versus TC smokers smoked the TC (5.75 ± 0.74 vs. 5.88 ± 0.69 ng/mL, P = 0.47), acute EC vaping did not impair FMD. In otherwise healthy young people who regularly smoke TCs or ECs, impaired FMD compared with that in nonsmokers was not present at baseline. However, FMD was significantly impaired after smoking one TC, but not after vaping an equivalent "dose" (estimated by change in plasma nicotine) of an EC, consistent with the notion that non-nicotine constituents in TC smoke mediate the impairment. Although it is reassuring that acute EC vaping did not acutely impair FMD, it would be dangerous and premature to conclude that ECs do not lead to atherosclerosis.NEW & NOTEWORTHY In our study of otherwise healthy young people, baseline flow-mediated dilation (FMD), a predictor of atherosclerosis and increased cardiovascular risk, was not different among tobacco cigarette (TC) smokers or electronic cigarette (EC) vapers who had refrained from smoking, compared with nonsmokers. However, acutely smoking one TC impaired FMD in smokers, whereas vaping a similar EC "dose" (as estimated by change in plasma nicotine levels) did not. Finally, although it is reassuring that acute EC vaping did not acutely impair FMD, it would be premature and dangerous to conclude that ECs do not lead to atherosclerosis or increase cardiovascular risk.

Neurocognition in treatment-resistant hypertension: profile and associations with cardiovascular biomarkers

BACKGROUND

Hypertension in midlife has been associated with increased risk of stroke and neurocognitive decline. Few studies, however, have examined neurocognition among individuals with treatment-resistant hypertension or potential mechanisms by which treatment-resistant hypertension may impair neurocognition.

METHODS

We examined the pattern of neurocognitive impairment and potential mechanisms in a sample of 96 overweight adults with treatment-resistant hypertension, aged 41-81 years. Neurocognitive function was assessed using a 45-min test battery consisting of executive function and memory. Vascular and metabolic mechanisms examined included cerebrovascular risk factors (CVRFs: Framingham Stroke Risk Profile), insulin sensitivity (homeostatic model assessment of insulin resistance), waist-to-hip ratio, microvascular function (hyperemic response), and peak oxygen consumption from an exercise treadmill test. Simple path analyses were used to assess the association between potential vascular and metabolic mechanisms and neurocognition.

RESULTS

Neurocognitive impairments were common, with 70% of the sample exhibiting impaired performance on at least one executive function subtest and 38% on at least one measure of memory. Higher levels of aerobic fitness, greater insulin sensitivity, and better microvascular function, as well as lower CVRFs and waist-to-hip ratio were associated with better neurocognition. In path analyses, aerobic fitness, microvascular function, and CVRFs all were independently associated with neurocognitive performance. Insulin resistance associated with worse executive function but better memory performance among older participants.

CONCLUSION

Neurocognitive impairments are common in adults with treatment-resistant hypertension, particularly on tests of executive function. Better neurocognition is independently associated with aerobic fitness, microvascular function, and CVRFs.

Chronic antioxidant administration restores macrovascular function in patients with heart failure with reduced ejection fraction

NEW FINDINGS

What is the central question of this study? We aimed to examine oxidative stress, antioxidant capacity and macro- and microvascular function in response to 30 days of oral antioxidant administration in patients with heart failure with reduced ejection fraction. What is the main finding and its importance? We observed an approximately twofold improvement in macrovascular function, assessed via brachial artery flow-mediated dilatation, and a reduction in oxidative stress after antioxidant administration in patients with heart failure with reduced ejection fraction. The improvement in macrovascular function was reversed 1 week after treatment cessation. These findings have identified the potential of oral antioxidant administration to optimize macrovascular health in this patient group.

ABSTRACT

Heart failure with reduced ejection fraction (HFrEF) is characterized by macrovascular dysfunction and elevated oxidative stress that may be mitigated by antioxidant (AOx) administration. In this prospective study, we assessed flow-mediated dilatation (FMD) and reactive hyperaemia responses in 14 healthy, older control participants and 14 patients with HFrEF, followed by 30 days of oral AOx administration (1 g vitamin C, 600 I.U. vitamin E and 0.6 g α-lipoic acid) in the patient group. Blood biomarkers of oxidative stress (malondialdehyde) and AOx capacity (ferric reducing ability of plasma) were also assessed. Patients with HFrEF had a lower %FMD (2.63 ± 1.57%) than control participants (5.62 ± 2.60%), and AOx administration improved %FMD in patients with HFrEF (30 days, 4.90 ± 2.38%), effectively restoring macrovascular function to that of control participants. In a subset of patients, we observed a progressive improvement in %FMD across the treatment period (2.62 ± 1.62, 4.23 ± 2.69, 4.33 ± 2.24 and 4.97 ± 2.56% at days 0, 10, 20 and 30, respectively, n = 12) that was abolished 7 days after treatment cessation (2.99 ± 1.78%, n = 9). No difference in reactive hyperaemia was evident between groups or as a consequence of the AOx treatment. Ferric reducing ability of plasma levels increased (from 6.08 ± 2.80 to 6.70 ± 1.59 mm, day 0 versus 30) and malondialdehyde levels decreased (from 6.81 ± 2.80 to 6.22 ± 2.84 μm, day 0 versus 30) after treatment. These findings demonstrate the efficacy of chronic AOx administration in attenuating oxidative stress, improving AOx capacity and restoring macrovascular function in patients with HFrEF.

Reactive hyperemia: a review of methods, mechanisms, and considerations

Reactive hyperemia is a well-established technique for noninvasive assessment of peripheral microvascular function and a predictor of all-cause and cardiovascular morbidity and mortality. In its simplest form, reactive hyperemia represents the magnitude of limb reperfusion following a brief period of ischemia induced by arterial occlusion. Over the past two decades, investigators have employed a variety of methods, including brachial artery velocity by Doppler ultrasound, tissue reperfusion by near-infrared spectroscopy, limb distension by venous occlusion plethysmography, and peripheral artery tonometry, to measure reactive hyperemia. Regardless of the technique used to measure reactive hyperemia, blunted reactive hyperemia is believed to reflect impaired microvascular function. With the advent of several technological advancements, together with an increased interest in the microcirculation, reactive hyperemia is becoming more common as a research tool and is widely used across multiple disciplines. With this in mind, we sought to review the various methodologies commonly used to assess reactive hyperemia and current mechanistic pathways believed to contribute to reactive hyperemia and reflect on several methodological considerations.

Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise

Muscle sympathetic nerve activity (MSNA) decreases during low-intensity dynamic one-leg exercise in healthy subjects but increases in patients with heart failure with reduced ejection fraction (HFrEF). We hypothesized that increased peak oxygen uptake (V̇o_2peak) after aerobic training would be accompanied by less sympathoexcitation during both mild and moderate one-leg dynamic cycling, an attenuated muscle metaboreflex, and greater skin vasodilation. We studied 27 stable, treated HFrEF patients (6 women; mean age: 65 ± 2 SE yr; mean left ventricular ejection fraction: 30 ± 1%) and 18 healthy age-matched volunteers (6 women; mean age: 57 ± 2 yr). We assessed V̇o_2peak (open-circuit spirometry) and the skin microcirculatory response to reactive hyperemia (laser flowmetry). Fibular MSNA (microneurography) was recorded before and during one-leg cycling (2 min unloaded and 2 min at 50% of V̇o_2peak) and, to assess the muscle metaboreflex, during posthandgrip ischemia (PHGI). HFrEF patients were evaluated before and after 6 mo of exercise-based cardiac rehabilitation. Pretraining V̇o_2peak and skin vasodilatation were lower (P < 0.001) and resting MSNA higher (P = 0.01) in HFrEF than control subjects. Training improved V̇o_2peak (+3.0 ± 1.0 mL·kg^-1·min^-1; P < 0.001) and cutaneous vasodilation and diminished resting MSNA (-6.0 ± 2.0, P = 0.01) plus exercise MSNA during unloaded (-4.0 ± 2.5, P = 0.04) but not loaded cycling (-1.0 ± 4.0 bursts/min, P = 0.34) and MSNA during PHGI (P < 0.05). In HFrEF patients, exercise training lowers MSNA at rest, desensitizes the sympathoexcitatory metaboreflex, and diminishes MSNA elicited by mild but not moderate cycling. Training-induced downregulation of resting MSNA and attenuated reflex sympathetic excitation may improve exercise capacity and survival.

Interindividual differences in the ischemic stimulus and other technical considerations when assessing reactive hyperemia

Reactive hyperemia is an established, noninvasive technique to assess microvascular function and a powerful predictor of all-cause and cardiovascular morbidity and mortality. Emerging evidence from our laboratory suggests a close link between reactive hyperemia and the metabolic rate of the ischemic limb and the existence of large interindividual differences contributing to markedly different stimuli to vasodilate. Here we relate forearm tissue desaturation (i.e., the ischemic stimulus to vasodilate, measured by near-infrared spectroscopy) to brachial artery hyperemic velocity and flow (measured using duplex ultrasound) across a wide range of ischemic stimuli. Twelve young and 11 elderly individuals were prospectively studied. To recapitulate conventional vascular occlusion testing, reactive hyperemia was first assessed using a standard 5-min occlusion period. Then, to evaluate the dose dependence of tissue ischemia on reactive hyperemia, we randomly performed 4-, 6-, and 8-min cuff occlusions in both groups. In all cases, peak velocity, as well as the 5-s average velocity, immediately after the cuff occlusion was significantly higher in the young than the elderly group; however, tissue desaturation was also much more pronounced in the young group (P < 0.05), representing a greater ischemic stimulus. Remarkably, when reactive hyperemia was adjusted for the ischemic vasodilatory stimulus, group differences in reactive hyperemia were abrogated. Together, these data challenge conventional interpretations of reactive hyperemia and show that the ischemic stimulus to vasodilate varies across individuals and that the level of reactive hyperemia is often coupled to the magnitude of tissue desaturation.

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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Application of non-invasive detection of peripheral vascular dysfunction in ovarian hyperstimulation syndrome (OHSS): A pilot study of clinical relevance

OBJECTIVE

The current study tested the hypothesis that vascular endothelial function, as reflected by the reactive hyperemia index (RHI), and biochemical factors, including VEGF, TNFα, CRP, inhibin A, and inhibin B, were involved in the pathogenesis of ovarian hyperstimulation syndrome (OHSS).

MATERIALS AND METHODS

This study was conducted between June 2010 and June 2012, enrolling 15 patients with OHSS and 6 healthy control subjects <45 years of age. Detailed clinical parameters were reviewed, including serum VEGF, TNFα, CRP, inhibin A, inhibin B, and hematocrit. RHI assessed by novel automatic peripheral arterial tonography was used to evaluate the vascular endothelial function.

RESULTS

Twenty-one subjects were evaluated. There was no significant difference between patients with OHSS and control subjects with respect to VEGF, TNFα, CRP, inhibin A and inhibin B. The RHI was not significantly different between patients with OHSS and control subjects (mean, 1.8 ± 0.4 vs. 1.7 ± 0.2). The hematocrit was significantly different between patients with OHSS and control subjects.

CONCLUSIONS

Our preliminary data did not reveal direct evidence of vascular endothelial dysfunction in patients with OHSS. To identify whether RHI could reflect vascular endothelial dysfunction in patients with OHSS, more cases with different severities of OHSS should be recruited in the future study.

Endothelial dysfunction and heart failure: A review of the existing bibliography with emphasis on flow mediated dilation

Heart failure affects 1–2% of the population worldwide, and it is characterized by episodes of decompensation often requiring hospitalization. Although targeted treatment has reduced the prevalence of rehospitalizations to 30–50%, mortality rates remain high. A complex blend of structural and functional alterations accounts for the genesis and progression of heart failure, but the exact underlying pathophysiology remains poorly understood. The aim of this review is to summarize endothelial dysfunction and its role in the pathogenesis and progression of heart failure. Moreover, it sums up all the appropriate methods of assessing endothelial dysfunction emphasizing on flow-mediated dilation and introduces endothelium as a potential target for new therapeutic development and research in the wide spectrum of the syndrome called heart failure.

Microvascular Endothelial Function and Neurocognition Among Adults With Major Depressive Disorder

BACKGROUND

Cardiovascular risk factors (CVRFs) and endothelial dysfunction have been associated independently with poorer neurocognition in middle-aged adults, particularly on tests of frontal lobe function. However, to our knowledge, no studies have examined markers of microvascular dysfunction on neurocognition or the potential interaction between macro- and microvascular biomarkers on neurocognition in middle-aged and older adults with major depressive disorder (MDD).

METHODS

Participants included 202 adults with MDD who were not receiving mental health treatment. Microvascular endothelial function was assessed using a noninvasive marker of forearm reactive hyperemia velocity while macrovascular endothelial function was assessed using flow-mediated dilation (FMD) of the brachial artery. CVRFs were assessed using the Framingham Stroke Risk Profile and fasting lipid levels. A standardized neurocognitive assessment battery was used to assess three cognitive domains: executive function, working memory, and verbal memory.

RESULTS

Greater microvascular dysfunction was associated with poorer neurocognition across all three domains. Microvascular function continued to predict verbal memory performance after accounting for background factors and CVRFs. Macro- and microvascular function interacted to predict working memory performance (F = 4.51_{1, 178}, p = 0.035), with a similar nonsignificant association for executive function (F = 2.73_{1, 178}, p = 0.095), with moderate associations observed between microvascular function and neurocognition in the presence of preserved FMD (r₆₁ = 0.40, p = 0.001), but not when FMD was impaired (r₆₃ = -0.05, p = 0.675).

CONCLUSION

Greater microvascular dysfunction is associated with poorer neurocognition among middle-aged and older adults. This association was strongest in participants with preserved macrovascular function.

Sex Differences in the Cerebral Collateral Circulation

Premenopausal women and intact female rodents sustain smaller cerebral infarctions than males. Several sex-dependent differences have been identified as potential contributors, but many questions remain unanswered. Mice exhibit wide variation in native collateral number and diameter (collateral extent) that is dependent on differences in genetic background, aging, and other comorbidities and that contributes to their also-wide differences in infarct volume. Likewise, variation in infarct volume correlates with differences in collateral-dependent blood flow in patients with acute ischemic stroke. We examined whether extent of pial collateral arterioles and posterior communicating collateral arteries (PComAs) differ depending on sex in young, aged, obese, hypertensive, and genetically different mice. We combined new data with meta-analysis of our previously published data. Females of C57BL/6J (B6) and BALB/cByJ (BC) strains sustained smaller infarctions than males after permanent MCA occlusion. This protection was unchanged in BC mice after introgression of the B6 allele of Dce1, the major genetic determinant of variation in pial collaterals among mouse strains. Consistent with this, collateral extent in these and other strains did not differ with sex. Extent of PComAs and primary cerebral arteries also did not vary with sex. No dimorphism was evident for loss of pial collateral number and/or diameter (collateral rarefaction) caused by aging, obesity, and hypertension, nor for collateral remodeling after pMCAO. However, rarefaction was greater in females with long-standing hypertension. We conclude that smaller infarct volume in female mice is not due to greater collateral extent, greater remodeling, or less rarefaction caused by aging, obesity, or hypertension.