Femoral Blood Flow Research Articles

Altered Vascular Endothelium-Dependent Responsiveness in Frail Elderly Patients Recovering from COVID-19 Pneumonia: Preliminary Evidence.

We evaluated vascular dysfunction with the single passive leg movement test (sPLM) in 22 frail elderly patients at 84 + 31 days after hospitalization for COVID-19 pneumonia, compared to 22 age-, sex- and comorbidity-matched controls (CTRL). At rest, all COVID-19 patients were in stable clinical condition without severe comorbidities. Patients (aged 72 ± 6 years, 73% male) had moderate disability (Barthel index score 77 ± 26), hypoxemia and normocapnia at arterial blood gas analysis and mild pulmonary restriction at spirometry. Values of circulating markers of inflammation (C-reactive protein: CRP; erythrocyte sedimentation rate: ESR) and coagulation (D-dimer) were: 27.13 ± 37.52 mg/dL, 64.24 ± 32.37 mm/1 h and 1043 ± 729 ng/mL, respectively. At rest, femoral artery diameter was similar in COVID-19 and CTRL (p = 0.16). On the contrary, COVID-19 infection deeply impacted blood velocity (p = 0.001) and femoral blood flow (p < 0.0001). After sPLM, peak femoral blood flow was dramatically reduced in COVID-19 compared to CTRL (p = 0.001), as was blood flow ∆peak (p = 0.05) and the area under the curve (p < 0.0001). This altered vascular responsiveness could be one of the unknown components of long COVID-19 syndrome leading to fatigue, changes in muscle metabolism and fibers’ composition, exercise intolerance and increased cardiovascular risk. Impact of specific treatments, such as exercise training, dietary supplements or drugs, should be evaluated.

Use of electrical muscle stimulation body massager (EMS-BMs) improves deep venous blood flow

We investigated whether using electrical muscle stimulation body massagers (EMS-BMs) for the passive contraction of the lower extremity muscles reduces venous stasis in the deep veins of the lower extremities. In this randomized crossover design study of 20 healthy volunteers between November 2018 and February 2019, we measured both the popliteal and femoral vein peak velocities (PV, cm/s) and blood flow volumes (BFV,mL/min), using pulsed-wave Doppler ultrasound at rest (baseline), and at 2 and 10 min after starting EMS-BM use. Two EMS types: types A (two small pads) and B (one large pad) devices respectively, were examined. The PVs of the femoral (A: 23±7, B: 25±8) and popliteal (A: 26±12, B: 27±12) veins and BFV of types A (107±46) and B (141±88) of the femoral vein were significantly increased compared to the baseline (PV of femoral vein: 19±9, PV of popliteal vein: 14±5, BFV of popliteal vein: 81±46) (P<0.01). No significant differences occurred between the devices in the PV or BFV at either 2 or 10 min. Regardless of the type of stimulation or the shape of the pad, contraction of the lower limb muscles by EMS-BM effectively reduces venous stasis in the lower limb.

Acute Effects of Short‐term Warm Water Immersion on Vascular Function

Cardiovascular disease (CVD) is a leading cause of death in the world. Currently, effective strategies for preventing CVD have been developed extensively. CVD is characterized by vascular dysfunction, including the decreased endothelial-dependent vasodilation and the increased arterial stiffness. In this line, regular physical activity (i.e., aerobic exercise) is one of the most established treatments of the primary prevention of CVD because it may restore impaired vascular function. However, not all populations can engage in physical activities. Thus, substitute interventions on vascular hemodynamics are needed for individuals with physical disabilities. Warm water immersion (WWI) has a potentially favorable effect on vascular health. However; the effects of short-term WWI on vascular function remain unclear. The present study aimed to determine the acute effects of short-term WWI on vascular function in healthy men. Ten healthy men (27-57 years, 44±12 years of mean age) underwent 5-minute WWI (40-41ºC) at the heart level. Heart rate, blood pressure (BP), aortic and leg pulse wave velocity (PWV), and femoral arterial blood flow and shear rate (SS) were measured before and 10 minutes after WWI. After 5-minute WWI, heart rate and brachial diastolic BP were significantly decreased. Aortic and leg PWV were decreased by 7.5% and 3.1%, respectively (P=0.006 and P=0.049). Femoral arterial blood flow was increased by 45.9% (P=0.002) and leg vascular resistance was decreased by 29.1% (P<0.001). Change in leg PWV was significantly correlated with corresponding change in femoral arterial blood flow (r = - 0.713, P = 0.181) and SS (r = - 0.724, P = 0.154). Our results indicate that a short-term WWI acutely improves vascular function. Further studies to determine the interaction between the residual effect of a single bout of short-term WWI and chronic change (e.g., adaptation) in vascular function are needed.

Electrical Stimulation of Afferent Lumbar Sympathetic Nerve Impacts Cardio‐Respiratory Functions in Anesthetized Rats

The lumbar sympathetic chains (LSC) contain post-ganglionic vasodilator and vasoconstrictor fibers that control hindlimb vascular tone. The LSC also contain dorsal root ganglion afferent fibers whose roles in cardiorespiratory status remain poorly understood. The objective of the present study was to characterize the cardiorespiratory responses elicited by electrical stimulation (ES) of a LSC in urethane-anaesthetized male Sprague-Dawley rats (n=6) instrumented to measure/calculate mean arterial blood pressure (MAP), femoral artery blood flow (FBF) and femoral vascular resistance (FVR), brachial artery blood flow (BBF), and brachial vascular resistances (BVR), upper airway pressure (UAP), diaphragmatic EMG, respiratory frequency, inspiratory (iTV) and expiratory (eTV) tidal volumes. The right LSC was identified at the level of L4-L6 and a bipolar electrode was placed for ES (5 Hz, 0.5 msec duration, 0.5 mA amplitude for 10 sec). LSC stimulation caused a distinct pattern of cardiorespiratory responses including (a) a 12% decrease in MAP, (b) 15% decrease in ipsilateral FVR, (c) a 10% decrease in BVR (all measured at the peak decrease in MAP), (d) a 15% increase in iVT, (e) a 10% increase in eVT, (f) a15% increase in respiratory frequency, and (g) a 9% increase in diaphragmatic EMG activity. The result of this study demonstrates that ES of afferent fibers within the LSC elicits an array of cardiorespiratory changes in anesthetized rats that would be consistent with preparing the rats for exercise and for flight.

Differential Vasomotor Effects of Insulin in the Peripheral and Cerebrovascular Circulations of Healthy Young Adults

Background Insulin-stimulated peripheral and cerebrovascular vasodilation are consistently observed in preclinical animal models. Hyperinsulinemia also has profound vasodilatory effects within the skeletal muscle vasculature in healthy young adults; however, the magnitude of insulin-stimulated cerebrovascular vasodilation in humans remains unclear. We hypothesized insulin-stimulated vasodilation would be observed in both the peripheral and cerebral circulations in healthy young adults. Methods Middle cerebral artery velocity (MCAv) was measured with transcranial Doppler ultrasound in 9 healthy young adults (4M/5F, 28±2 yrs, 24±1 kg/m2) at baseline and following a 60-min hyperinsulinemic (40 mU/m2 body surface area/min), euglycemic infusion. Femoral artery diameter and mean blood velocity were measured by Doppler ultrasound to determine femoral artery blood flow (FBF). Mean arterial blood pressure (MABP) was measured continuously by finger photoplethysmography. Cerebrovascular conductance index (CVCi = MCAv/MABP x 100) and femoral vascular conductance (FVC = FBF/MABP x 100) were calculated. Results Intravenous insulin infusion resulted in an increase in plasma insulin (5±1 to 41±2 µIU/mL, p<0.01) with blood glucose maintained at baseline levels (75±2 to 72±4 mg/dL, p=0.48). MABP was maintained throughout the infusion protocol (85±3 to 88±3 mmHg, p=0.21). There was a significant increase in FBF (134±24 to 184±30 mL/min, p=0.05) and FVC (153±22 to 211±31 mL/min/100 mmHg, p=0.04) during hyperinsulinemia. In contrast, there was no effect of hyperinsulinemia on MCAv (54±3 to 51±3 cm/s, p=0.28) or CVCi (65±5 to 58±3 AU, p=0.14). There was no association between insulin-stimulated peripheral and cerebrovascular vasodilation (R=-0.421, p=0.26). Conclusions Hyperinsulinemia in healthy young adults elicits peripheral vasodilation. Contrary to our hypothesis, following a 60-minute systemic intravenous insulin infusion there is no change in MCAv or CVCi in healthy young adults. These data indicate the cerebral and peripheral vasculature are differentially regulated during hyperinsulinemia.

Reduced post-exercise muscle microvascular perfusion with compression is offset by increased muscle oxygen extraction: Assessment by contrast-enhanced ultrasound.

The microvasculature is important for both health and exercise tolerance in a range of populations. However, methodological limitations have meant changes in microvascular blood flow are rarely assessed in humans during interventions designed to affect skeletal muscle blood flow such as the wearing of compression garments. The aim of this study is, for the first time, to use contrast-enhanced ultrasound to directly measure the effects of compression on muscle microvascular blood flow alongside measures of femoral artery blood flow and muscle oxygenation following intense exercise in healthy adults. It was hypothesized that both muscle microvascular and femoral artery blood flows would be augmented with compression garments as compared with a control condition. Ten recreationally active participants completed two repeated-sprint exercise sessions, with and without lower-limb compression tights. Muscle microvascular blood flow, femoral arterial blood flow (2D and Doppler ultrasound), muscle oxygenation (near-infrared spectroscopy), cycling performance, and venous blood samples were measured/taken throughout exercise and the 1-hour post-exercise recovery period. Compared with control, compression reduced muscle microvascular blood volume and attenuated the exercise-induced increase in microvascular velocity and flow immediately after exercise and 1hour post-exercise. Compression increased femoral artery diameter and augmented the exercise-induced increase in femoral arterial blood flow during exercise. Markers of blood oxygen extraction in muscle were increased with compression during and after exercise. Compression had no effect on blood lactate, glucose, or exercise performance. We provide new evidence that lower-limb compression attenuates the exercise-induced increase in skeletal muscle microvascular blood flow following exercise, despite a divergent increase in femoral artery blood flow. Decreased muscle microvascular perfusion is offset by increased muscle oxygen extraction, a potential mechanism allowing for the maintenance of exercise performance.

Chemotherapy-induced acute vascular injury involves intracellular generation of ROS via activation of the acid sphingomyelinase pathway

Several categories of chemotherapy confer substantial risk for late-term vascular morbidity and mortality. In the present study, we aimed to investigate the mechanism of acute chemotherapy-induced vascular injury in normal tissues. Specifically, we looked at activation of the acid sphingomyelinase (ASMase)/ceramide pathway, which leads to generation of reactive oxygen species (ROS) and induction of oxidative stress that may result in vascular injury.In particular, we focused on two distinct drugs, doxorubicin (DOX) and cisplatin (CIS) and their effects on normal endothelial cells. In vitro, DOX resulted in increased ASMase activity, intra-cellular ROS production and induction of apoptosis. CIS treatment generated significantly reduced effects in endothelial cells. In-vivo, murine femoral arterial blood flow was measured in real-time, during and after DOX or CIS administration, using fluorescence optical imaging system. While DOX caused constriction of small vessels and disintegration of large vessels' wall, CIS induced minor vascular changes in arterial blood flow, correlating with the in vitro findings. These results demonstrate that DOX induces acute vascular injury by increased ROS production, via activation of ASMase/ceramide pathway, while CIS increases ROS production and its immediate extracellular translocation, without causing detectable acute vascular injury. Our findings may potentially lead to the development of new strategies to prevent long-term cardiovascular morbidity in cancer survivors.

Acute Effects of Short-Term Warm Water Immersion on Arterial Stiffness and Central Hemodynamics.

Warm water immersion (WWI) has a potentially favorable effect on vascular health. However, the effects of short-term WWI on vascular function and central hemodynamics remain unclear. The present study aimed to determine the acute effects of short-term WWI on arterial stiffness and central hemodynamics in healthy men. Ten healthy men (27–57 years, 44 ± 12 years of mean age) underwent 5-min WWI (40–41°C) at the heart level. Systemic hemodynamics and tympanic temperature were monitored during WWI. Furthermore, pulse wave velocity (PWV) and aortic hemodynamics were measured before and 10 min after WWI. Cardiac output (CO) (via the Modelflow method) increased (P = 0.037), whereas tympanic temperature did not change (P = 0.879) during WWI. After 5-min WWI, heart rate (HR) and brachial diastolic blood pressure (BP) were significantly decreased. Aortic and leg PWV were decreased by 7.5 and 3.1%, respectively (P = 0.006 and P = 0.040). Femoral arterial blood flow was increased by 45.9% (P = 0.002), and leg vascular resistance was decreased by 29.1% (P < 0.001). Regarding central hemodynamic variables (estimated by general transfer function), aortic BP and augmentation index (AIx) did not change significantly, but the subendocardial viability ratio (SEVR), an index of coronary perfusion, was increased (P = 0.049). Our results indicate that a short-term WWI acutely improves aortic and peripheral arterial stiffness and coronary perfusion. Further studies to determine the interaction between the residual effect of a single bout of short-term WWI and chronic change (e.g., adaptation) in arterial stiffness and central hemodynamics are needed.

Lack of evidence for impaired preload or Bezold-Jarisch activation during brief umbilical cord occlusions in fetal sheep.

Impaired cardiac preload secondary to umbilical cord occlusion (UCO) has been hypothesized to contribute to intrapartum decelerations, brief falls in fetal heart rate (FHR), through activation of the Bezold-Jarisch reflex. This cardioprotective reflex increases parasympathetic and inhibits sympathetic outflows triggering hypotension, bradycardia, and peripheral vasodilation, but its potential to contribute to intrapartum decelerations has never been systematically examined. In this study, we performed bilateral cervical vagotomy to remove the afferent arm and the efferent parasympathetic arm of the Bezold-Jarisch reflex. Twenty-two chronically instrumented fetal sheep at 0.85 of gestation received vagotomy (n = 7) or sham vagotomy (control, n = 15), followed by three 1-min complete UCOs separated by 4-min reperfusion periods. UCOs in control fetuses were associated with a rapid fall in FHR and reduced femoral blood flow mediated by intense femoral vasoconstriction, leading to hypertension. Vagotomy abolished the rapid fall in FHR (P < 0.001) and, despite reduced diastolic filling time, increased both carotid (P < 0.001) and femoral (P < 0.05) blood flow during UCOs, secondary to carotid vasodilation (P < 0.01) and delayed femoral vasoconstriction (P < 0.05). Finally, vagotomy was associated with an attenuated rise in cortical impedance during UCOs (P < 0.05), consistent with improved cerebral substrate supply. In conclusion, increased carotid and femoral blood flows after vagotomy are consistent with increased left and right ventricular output, which is incompatible with the hypothesis that labor-like UCOs impair ventricular filling. Overall, the cardiovascular responses to vagotomy do not support the hypothesis that the Bezold-Jarisch reflex is activated by UCO. The Bezold-Jarisch reflex is therefore mechanistically unable to contribute to intrapartum decelerations.

Comparison of a nonpneumatic device to four currently available intermittent pneumatic compression devices on common femoral blood flow dynamics

ObjectiveThe purpose of the present study was to compare common femoral vein blood flow enhancement during external mechanical compression using the novel, nonpneumatic Recovery Force Health Movement and Compressions (MAC) System (Recovery Force USA, Fishers, Ind), and four currently available intermittent pneumatic compression devices. MethodsThe MAC device was compared with the Kendall SCD 700 (Cardinal Health, Dublin, Ohio), Arjo Huntleigh Flowtron ACS900 (Arjo, Malmö, Sweden), ActiveCare+S.F.T. (Zimmer Biomet, Warsaw, Ind), and Circul8 (Ortho8, Rocklin, Calif). Doppler ultrasound measurements for each device were directly obtained from the right common femoral vein by a registered vascular technologist. The peak flow velocity and the time taken to reach the peak were calculated. For the MAC system only, the subjects were asked to walk a minimum of 500 steps while wearing the system, which was then checked for slippage. Leg size measurements were obtained using the noncontact Sigvaris Legreader XT5 (Vialis Ortopedia, Turin, Italy). The MAC device is not yet commercially available, and the present study was a prequel to clinical studies of venous thromboembolism prevention. ResultsWe recruited a broad range of 20 subjects who varied in age (mean ± standard deviation [SD], 50.5 ± 16.2 years), body mass index (mean ± SD, 26 ± 5.5 kg/m2), gender (male, 25%; female, 75%), and right calf circumference (mean ± SD, 37.2 ± 5.5 cm). The peak flow velocity compared with the baseline measurements was significantly greater for the Recovery Force Health MAC System for three (Kendall SCD 700, P = .02; ActiveCare+S.F.T., P = .003; Circul8, P < .001) of the four comparisons. Although the difference was not significant, the Arjo Huntleigh Flowtron ACS900 (SD, 3.4 cm/s) had more measurement variability in the peak flow velocity compared with baseline than did the MAC System (SD, 1.9 cm/s). The MAC had a significantly (P < .001) faster rise time to peak flow compared with the comparison devices. It was the only device to achieve the target peak flow velocity over baseline of at least three times in every body mass index group. Finally, the MAC System met the goal of <2.5 cm of movement after ambulation in 100% of the measurements, with 75% of the measurements showing no movement. ConclusionsThe MAC System is a mobile device that remained in place during ambulation and provided more consistent external mechanical compression in the desired range compared with the other three devices included in the present study.

The effects of local versus systemic passive heating on the acute inflammatory, vascular and glycaemic response.

The aim of this study was to compare the acute cardiometabolic and perceptual responses between local and whole-body passive heating. Using a water-perfused suit, 10 recreationally active males underwent three 90 min conditions: heating of the legs with upper-body cooling (LBH), whole-body heating (WBH) and exposure to a thermoneutral temperature (CON). Blood samples were collected before and up to 3 h post-session to assess inflammatory markers, while a 2 h oral glucose tolerance test was initiated 1 h post-session. Femoral artery blood flow and perceptual responses were recorded at regular intervals. The interleukin (IL)-6 incremental area under the curve (iAUC) was higher for LBH (1096 ± 851 pg/mL × 270 min) and WBH (833 ± 476 pg/mL × 270 min) compared with CON (565 ± 325 pg/mL × 270 min; p < 0.047). Glucose concentrations were higher after WBH compared with LBH and CON (p < 0.046). Femoral artery blood flow was higher at the end of WBH (1713 ± 409 mL/min) compared with LBH (943 ± 349 mL/min; p < 0.001), and higher in LBH than CON (661 ± 222 mL/min; p = 0.002). Affect and thermal comfort were more negative during WBH compared with LBH and CON (p < 0.010). In conclusion, local passive heating elevated blood flow and the IL-6 iAUC. However, while resulting in more positive perceptual responses, the majority of the included cardiometabolic markers were attenuated compared with WBH. Novelty: The increase in the IL-6 iAUC in response to passive heating is not reduced by upper-body cooling. Upper-body cooling attenuates the plasma nitrite, IL-1ra and femoral artery blood flow response to passive heating. Upper-body cooling leads to more positive perceptual responses to passive heating.

Homebased Standing Core Exercise Training Improves Femoral Blood Flow but not Arterial Stiffness in Middle-Aged to Older Adults

Homebased exercise is often advocated to improve physical fitness in the aging population, especially when outdoor activity is not available. Yet we often have a limited understanding of its training effects for clinical uses.AimTo investigate a short-term exercise training of standing core exercise on femoral blood flow and vascular hemodynamic changes in middle-aged to the older population.MethodsA total of 34 middle-aged to older adults were recruited and randomly assigned into walking (M/F = 6/7, age = 66 ± 3 years), core exercise (M/F = 6/6, age = 66 ± 2 years), and the control group (M/F = 4/5, age = 70 ± 3 years). Carotid and brachial blood pressure, Carotid-femoral Pulse Wave Velocity (PWV) and Brachial-ankle PWV (baPWV), femoral blood flow and compliance, leg hemodynamics, as well as aerobic and muscular fitness (30 s arm curl and sit-to-stand test) were measured pre and post 8 weeks of exercise training (60–70% HRmax, three sessions/week).ResultsCore exercise group significantly increased femoral blood flow, but not overall vascular functions; arm muscle endurance and leg power performance were also significantly improved after training. The walking group significantly reduced baPWV, leg resistance, as well as increase femoral blood flow and compliance after training. Compared with the control, the core group elicited a higher femoral blood blow, whereas leg resistance was significantly reduced in the walking group after training.ConclusionA short-term standing core training appears to augment femoral blood flow and muscular fitness in middle-aged to older adults, yet walking is more effective in improving overall vascular health in this population.

Abnormal skeletal muscle blood flow, contractile mechanics and fibre morphology in a rat model of obese-HFpEF.

Key points Heart failure is characterised by limb and respiratory muscle impairments that limit functional capacity and quality of life. However, compared with heart failure with reduced ejection fraction (HFrEF), skeletal muscle alterations induced by heart failure with preserved ejection fraction (HFpEF) remain poorly explored.Here we report that obese‐HFpEF induces multiple skeletal muscle alterations in the rat hindlimb, including impaired muscle mechanics related to shortening velocity, fibre atrophy, capillary loss, and an impaired blood flow response to contractions that implies a perfusive oxygen delivery limitation.We also demonstrate that obese‐HFpEF is characterised by diaphragmatic alterations similar to those caused by denervation – atrophy in Type IIb/IIx (fast/glycolytic) fibres and hypertrophy in Type I (slow/oxidative) fibres.These findings extend current knowledge in HFpEF skeletal muscle physiology, potentially underlying exercise intolerance, which may facilitate future therapeutic approaches. Peripheral skeletal muscle and vascular alterations induced by heart failure with preserved ejection fraction (HFpEF) remain poorly identified, with limited therapeutic targets. This study used a cardiometabolic obese‐HFpEF rat model to comprehensively phenotype skeletal muscle mechanics, blood flow, microvasculature and fibre atrophy. Lean (n = 8) and obese‐HFpEF (n = 8) ZSF1 rats were compared. Skeletal muscles (soleus and diaphragm) were assessed for in vitro contractility (isometric and isotonic properties) alongside indices of fibre‐type cross‐sectional area, myosin isoform, and capillarity, and estimated muscle PO2. In situ extensor digitorum longus (EDL) contractility and femoral blood flow were assessed. HFpEF soleus demonstrated lower absolute maximal force by 22%, fibre atrophy by 24%, a fibre‐type shift from I to IIa, and a 17% lower capillary‐to‐fibre ratio despite increased capillary density (all P < 0.05) with preserved muscle PO2 (P = 0.115) and isometric specific force (P > 0.05). Soleus isotonic properties (shortening velocity and power) were impaired by up to 17 and 22%, respectively (P < 0.05), while the magnitude of the exercise hyperaemia was attenuated by 73% (P = 0.012) in line with higher muscle fatigue by 26% (P = 0.079). Diaphragm alterations (P < 0.05) included Type IIx fibre atrophy despite Type I/IIa fibre hypertrophy, with increased indices of capillarity alongside preserved contractile properties during isometric, isotonic, and cyclical contractions. In conclusion, obese‐HFpEF rats demonstrated blunted skeletal muscle blood flow during contractions in parallel to microvascular structural remodelling, fibre atrophy, and isotonic contractile dysfunction in the locomotor muscles. In contrast, diaphragm phenotype remained well preserved. This study identifies numerous muscle‐specific impairments that could exacerbate exercise intolerance in obese‐HFpEF.

Femoral arterial blood flow in the non-exercising leg increases during single-leg pedaling exercises

Femoral arterial blood flow in the non-exercising leg increases during single-leg pedaling exercises

Superficial femoral artery blood flow increases during middle intensity of arm cranking exercise in healthy male adults

Superficial femoral artery blood flow increases during middle intensity of arm cranking exercise in healthy male adults

Loss of ARNT Limits Improvement in Physiological Performance Following Aerobic Exercise in Aging

Hypoxia signaling is essential for angiogenesis and metabolic regulation during exercise. Our previous study has demonstrated an age-related loss of ARNT resulting in limited muscle regeneration. To explore the role of hypoxia signaling in physiological performance in relation to aging, we generated a mouse model with skeletal muscle-specific knockout of ARNT (ARNT mKO). ARNT mKO and ARNT WT mice were subjected to a sedentary activity or treadmill running exercise regime at an increasing speed of 8-12 m/min for 40 minutes, three times weekly over the course of 8 weeks. ARNT levels was 3-fold lower in old mice compared to young. The exercised WT mice exhibited 52% greater increase over the sedentary group in exercise endurance as measured by the maximum running distance (490.92±154.28 vs 237.76±135.19m, p＜0.01). In contrast, ARNT mKO mice did not benefit from exercise (231.85±198.61 vs 167.27±136.56m, p=0.41). The maximum running speed was severely restricted in the trained ARNT mKO mice versus WT (16±1.63 m/min vs 26.67±2.45 m/min, p＜0.001). Cross-sectional area of myofibers increased significantly following exercise in WT mice (2270 vs 2960 □m2, p=0,015) indicating muscle hypertrophic response, while no change was observed in the ARNT mKO group (2101 vs 2378□m2, p=0,21). Further, exercise increased femoral artery blood flow by 41% in ARNT WT mice, but not in ARNT mKO mice (898.96±52.33 vs 802.86±48.43, p=0.20). These data suggest that ARNT is essential for physiological response to exercise

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

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

Abstract 13868: Effects of Chronic Electronic Cigarette Vapor Exposures on the Cardiovascular Function in Rats

Background: We investigated the effects of chronic electronic cigarettes with nicotine (E-Cig) exposure on cardiovascular function in rats. Methods: Adult Sprague Dawley rats were exposed to either pure air (n=10) or E-Cig (n=14) for 12 weeks. After 12 weeks of exposure, flow-mediated vasodilation was measured in anesthetized rats with ultrasound to measure femoral artery diameter. Femoral artery flow velocity was measured before and 5 minutes after reperfusion of a 5-minute femoral artery occlusion. Cardiac function was assessed by echocardiogram. A Millar catheter was used to record systemic arterial and LV pressures. Cardiac output was measured using a themodilution catheter. Results: The femoral artery internal diameter and blood flow velocity were comparable between the 2 groups before and after artery occlusion. However, in the E-cig group, blood flow velocity significantly decreased from 55.5 ± 5.2 cm/s prior to occlusion to 41.3 ± 4.1 cm/s after reperfusion (p = 0.005); it remained similar prior to (47.8 ± 3.4 cm/s) and after (47.8 ± 5.5 cm/s) occlusion in the air group. There were no statistically significant differences in left ventricular diastolic and systolic dimensions, LV fractional shortening, heart rate or mean blood pressure (80 ± 3 mmHg in air and 79 ± 5 mmHg in E-cig group) , LV end-diastolic pressure (Ped), end-systolic pressure (Pes), peak -dP/dt, Tau, or cardiac output (48.3 ± 3.3 ml/min in air and 47.6 ± 3.9 ml/min in E-cig group) between the E-Cig and the pure air group. There was a trend toward a reduction in peak LV +dP /dt in the E-Cig group (5574 ± 341 mmHg/s) compared to the air group (6166 ± 238 mmHg/s). LV weight and wall thickness were similar between groups. Conclusions: Twelve weeks of E-Cig exposure did not affect heart rate or blood pressure; but did tend to reduce contractility. E-cigarette exposure slowed the flow-mediated blood flow velocity probably at a microvascular level, possibly by altering endothelial function.

Vascular alterations among young adults with SARS-CoV-2.

While SARS-CoV-2 primarily affects the lungs, the virus may be inflicting detriments to the cardiovascular system, both directly through angiotensin-converting enzyme 2 receptor and initiating systemic inflammation. Persistent systemic inflammation may be provoking vascular dysfunction, an early indication of cardiovascular disease risk. To establish the potential effects of SARS-CoV-2 on the systemic vasculature in the arms and legs, we performed a cross-sectional analysis of young healthy adults (control: 5 M/15 F, 23.0 ± 1.3 y, 167 ± 9 cm, 63.0 ± 7.4 kg) and young adults who, 3–4 wk prior to testing, had tested positive for SARS-CoV-2 (SARS-CoV-2: 4 M/7 F, 20.2 ± 1.1 y, 172 ± 12 cm, 69.5 ± 12.4 kg) (means ± SD). Using Doppler ultrasound, brachial artery flow-mediated dilation (FMD) in the arm and single passive limb movement (sPLM) in the leg were assessed as markers of vascular function. Carotid-femoral pulse wave velocity (PWVcf) was asvsessed as a marker of arterial stiffness. FMD was lower in the SARS-CoV-2 group (2.71 ± 1.21%) compared with the control group (8.81 ± 2.96%) (P < 0.01) and when made relative to the shear stimulus (SARS-CoV-2: 0.04 ± 0.02 AU, control: 0.13 ± 0.06 AU, P < 0.01). The femoral artery blood flow response, as evidenced by the area under the curve, from the sPLM was lower in the SARS-CoV-2 group (−3 ± 91 mL) compared with the control group (118 ± 114 mL) (P < 0.01). PWVcf was higher in the SARS-CoV-2 group (5.83 ± 0.62 m/s) compared with the control group (5.17 ± 0.66 m/s) (P < 0.01). Significantly lower systemic vascular function and higher arterial stiffness are evident weeks after testing positive for SARS-CoV-2 among young adults compared with controls.NEW & NOTEWORTHY This study was the first to investigate the vascular implications of contracting SARS-CoV-2 among young, otherwise healthy adults. Using a cross-sectional design, this study assessed vascular function 3–4 wk after young adults tested positive for SARS-CoV-2. The main findings from this study were a strikingly lower vascular function and a higher arterial stiffness compared with healthy controls. Together, these results suggest rampant vascular effects seen weeks after contracting SARS-CoV-2 in young adults.

The impact of preconditioning exercise on the vascular response to an oral glucose challenge.

Exercise elicits direct benefits to insulin sensitivity but may also indirectly improve glucose uptake by hemodynamic conditioning of the vasculature. The purpose of this study was to examine the modifying effect of 3 different types of exercise on the vascular response to an oral glucose challenge. Twenty healthy adults (9 women, 11 men; aged 23 ± 3 years) completed a standard oral glucose tolerance test (OGTT) at rest, as well as 1.5 hours after moderate continuous cycling exercise (30min; 65% peak oxygen consumption), high-intensity interval cycling exercise (10 × 1 min at 90% peak heart rate), and lower-load higher-repetition resistance exercise (25-35 repetitions/set, 3 sets). Brachial and superficial femoral artery blood flow, conductance, and oscillatory shear index were measured throughout the OGTT. Regardless of rested state or exercise preconditioning, the OGTT induced reductions in brachial artery blood flow and conductance (p< 0.001), and transient increases in brachial and superficial femoral artery oscillatory shear index and retrograde blood flow (p< 0.01). Continuous cycling and resistance exercise were followed with a small degree of protection against prolonged periods of oscillatory flow. Our findings imply transient peripheral vasoconstriction and decreased limb blood flow during a standard OGTT, for which prior exercise was unable to prevent in healthy adults. Novelty: We investigated the impact of continuous, interval, and resistance exercise on the hemodynamic response to an OGTT. Our findings suggest decreased upper-limb blood flow during an OGTT is not prevented by prior exercise in healthy adults.