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Stuckless TJR, Pyke KE. The impact of a cold pressor test on brachial artery handgrip exercise-induced flow-mediated dilation. Vasc Med 2015; 20:409-16. [DOI: 10.1177/1358863x15586473] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
It is unknown how endothelial-dependent flow-mediated dilation (FMD) stimulated by a sustained, exercise-induced increase in shear stress (EX-FMD) is affected by a simultaneous sympathoexcitatory painful stimulus. The purpose of this study was to examine the impact of a cold pressor test (CPT) on brachial artery EX-FMD elicited by a handgrip exercise-induced increase in shear stress. Participants were healthy males (age 21±2 years) ( n=28; 16 Experimental group, 12 Control). Brachial artery diameter and blood velocity were measured using echo and Doppler ultrasound, respectively. Shear stress was estimated by shear rate (shear rate = blood velocity / diameter) and targeted to reach 75 s–1 in each of two EX-FMD trials in all subjects. In the Experimental group, the second EX-FMD trial was accompanied by simultaneous foot immersion in ice water (simultaneous CPT). The shear rate stimulus did not differ between groups ( p=0.823) or trials ( p=0.726) (group × trial interaction: p=0.646) (average exercise shear rate (mean ± SD): 67.6±6.2 s–1). The CPT (experienced during EX-FMD trial 2 in the Experimental group) increased mean arterial pressure ( p<0.001) and heart rate ( p=0.002) relative to the Control group. %EX-FMD was not different between groups ( p=0.508) or trials ( p=0.592) (group × trial interaction: p=0.879) (EX-FMD: Experimental group trial 1: 5.4±3.4%, trial 2: 5.6±2.6%; Control group trial 1: 6.0±3.7%, trial 2: 6.4±2.2%). In conclusion, the CPT did not impact concurrent EX-FMD, and this indicates that an acute painful stimulus does not interfere with conduit artery FMD responses during exercise in young healthy men.
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Affiliation(s)
- Troy JR Stuckless
- School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada
| | - Kyra E Pyke
- School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada
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Peripheral conduit and resistance artery function are improved following a single, 1-h bout of peristaltic pulse external pneumatic compression. Eur J Appl Physiol 2015; 115:2019-29. [PMID: 25981709 DOI: 10.1007/s00421-015-3187-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 05/08/2015] [Indexed: 10/23/2022]
Abstract
INTRODUCTION External pneumatic compression (EPC) is being employed for a widening range of clinical and non-clinical populations. However, EPC devices vary markedly in treatment pressures, duty cycles and application sites, and the acute effects of whole limb, lower pressure EPC on peripheral vascular function have not been determined. PURPOSE The purpose of this study was to determine the acute effects of a single bout of peristaltic pulse EPC on peripheral conduit and resistance artery function. METHODS Twenty (n = 20; males = 12 and females = 8) young and apparently healthy subjects (aged 26.1 ± 8.2 years) participated in this study. A sequential EPC device with five inflation zones arranged linearly and inflating distal to proximal along the lower limbs was employed with target inflation pressures of 70 mmHg for 1 h. Flow-mediated dilation (FMD) of the brachial and popliteal arteries was evaluated with ultrasound before and after EPC. Venous occlusion plethysmography was employed to evaluate limb blood flow at rest and during reactive hyperemia (RH) in the forearm (FBF) and calf (CBF) before and after EPC. RESULTS Peak RH CBF was increased by 9 % after EPC (P < 0.05), whereas peak RH FBF (-10 %) did not change significantly (P > 0.25). Normalized popliteal artery FMD post-EPC (2.24 ± 1.41) was significantly higher than pre-EPC (1.36 ± 0.67, P = 0.015) and post-sham (1.58 ± 0.86, P = 0.032) values. Similarly, normalized brachial artery FMD post-EPC (1.47 ± 0.32) was significantly higher than pre-EPC (1.11 ± 0.41, P = 0.004) and post-sham (0.99 ± 0.27, P = 0.026) values. CONCLUSION Acutely, whole limb, lower pressure EPC improves conduit artery endothelial function systemically, but only improves RH blood flow locally (i.e., compressed limbs).
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Cardiovascular magnetic resonance imaging-based computational fluid dynamics/fluid-structure interaction pilot study to detect early vascular changes in pediatric patients with type 1 diabetes. Pediatr Cardiol 2015; 36:851-61. [PMID: 25577225 DOI: 10.1007/s00246-014-1071-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 11/27/2014] [Indexed: 12/19/2022]
Abstract
We hypothesized that pediatric patients with type 1 diabetes have cardiac magnetic resonance (CMR) detectable differences in thoracic aortic wall properties and hemodynamics leading to significant local differences in indices of wall shear stress, when compared with age-matched control subjects without diabetes. Pediatric patients with type 1 diabetes were recruited from Children's Hospital of Wisconsin and compared with controls. All underwent morning CMR scanning, 4-limb blood pressure, brachial artery reactivity testing, and venipuncture. Patient-specific computational fluid dynamics modeling with fluid-structure interaction, based on CMR data, determined regional time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Twenty type 1 diabetic subjects, median age 15.8 years (11.6-18.4) and 8 controls 15.4 years (10.3-18.2) were similar except for higher glucose, hemoglobin A1c, and triglycerides for type 1 diabetic subjects. Lower flow-mediated dilation was seen for those with type 1 diabetes (6.5) versus controls (7.8), p = 0.036. For type 1 diabetic subjects, the aorta had more regions with high TAWSS when compared to controls. OSI maps appeared similar. Flow-mediated dilation positively correlated with age at diabetes diagnosis (r = 0.468, p = 0.038) and hemoglobin A1c (r = 0.472, p = 0.036), but did not correlate with aortic distensibility, TAWSS, or OSI. TAWSS did not correlate with any clinical parameter for either group. CMR shows regional differences in aortic wall properties for young diabetic patients. Some local differences in wall shear stress indices were also observed, but a longitudinal study is now warranted.
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54
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Impaired brachial artery endothelial function in young healthy women following an acute painful stimulus. Eur J Appl Physiol 2015; 115:1547-57. [DOI: 10.1007/s00421-015-3139-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 02/19/2015] [Indexed: 10/23/2022]
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55
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Szijgyarto IC, Poitras VJ, Gurd BJ, Pyke KE. Acute psychological and physical stress transiently enhances brachial artery flow-mediated dilation stimulated by exercise-induced increases in shear stress. Appl Physiol Nutr Metab 2014; 39:927-36. [DOI: 10.1139/apnm-2013-0384] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exercise elevates conduit artery shear stress and stimulates flow-mediated dilation (FMD). However, little is known regarding the impact of acute psychological and physical stress on this response. The purpose of this study was to examine the impact of the Trier Social Stress Test (TSST (speech and arithmetic tasks)) and a cold pressor test (CPT) with and without social evaluation (SE) on exercise-induced brachial artery FMD (EX-FMD). A total of 59 healthy male subjects were randomly assigned to 1 of 3 conditions: TSST, CPT, or CPT with SE. During 6 min of handgrip exercise, brachial artery EX-FMD was assessed before and 15 and 35 min poststress with echo and Doppler ultrasound. Shear stress was estimated as shear rate, calculated as brachial artery mean blood velocity/brachial artery diameter. Results are means ± SD. All conditions elicited significant physiological stress responses. Salivary cortisol increased from 4.6 ± 2.4 nmol/L to 10.0 ± 5.0 nmol/L (p < 0.001; condition effect: p = 0.292). Mean arterial pressure increased from 98.6 ± 12.1 mm Hg to 131.9 ± 18.7 mm Hg (p < 0.001; condition effect: p = 0.664). Exercise shear rate did not differ between conditions (p = 0.592), although it was modestly lower poststress (prestress: 72.3 ± 4.5 s−1; 15 min poststress: 70.8 ± 5.4 s−1; 35 min poststress: 70.6 ± 6.1 s−1; trial effect: p = 0.011). EX-FMD increased from prestress to 15 min poststress in all conditions (prestress: 6.2% ± 2.8%; 15 min poststress: 7.9% ± 3.2%; 35 min poststress: 6.6% ± 2.9%; trial effect: p < 0.001; condition effect: p = 0.611). In conclusion, all conditions elicited similar stress responses that transiently enhanced EX-FMD. This response may help to support muscle perfusion during stress.
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Affiliation(s)
- Ingrid C. Szijgyarto
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Veronica J. Poitras
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Brendon J. Gurd
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Kyra E. Pyke
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
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56
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Scholten RR, Spaanderman MEA, Green DJ, Hopman MTE, Thijssen DHJ. Retrograde shear rate in formerly preeclamptic and healthy women before and after exercise training: relationship with endothelial function. Am J Physiol Heart Circ Physiol 2014; 307:H418-25. [PMID: 24906915 DOI: 10.1152/ajpheart.00128.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Blood flow patterns in conduit arteries characterized by high levels of retrograde shear stress can be detrimental for vascular health. In this study we examined whether retrograde shear rate and endothelial function are related in healthy and formerly preeclamptic (PE) women and whether this relationship is altered by exercise training. Formerly PE women (32 ± 4 yr, n = 20) and controls (32 ± 4 yr, n = 20), all 6-12 mo postpartum, performed 12-wk aerobic exercise training. We measured brachial artery shear rate (SR) and endothelial function by flow-mediated dilation (FMD, echo-Doppler). We additionally performed power spectral analysis of heart rate variability and calculated low-frequency/high-frequency (LF/HF) ratio. Antegrade SR was not different between groups, while retrograde SR was significantly higher and FMD% lower in PE women compared with controls (both P < 0.05). Retrograde shear correlated strongly with FMD% in PE women and controls (P < 0.05). LF/HF ratio inversely correlated with brachial artery retrograde SR and FMD% (both P < 0.05) in PE women and controls. Exercise training reduced retrograde shear, improved FMD%, and reduced LF/HF ratios similarly in both groups (all P < 0.05). Training-induced changes in retrograde SR correlated with changes in FMD% and LF/HF ratio. A higher brachial artery retrograde SR relates to lower brachial artery endothelial function, in both controls and formerly PE women. Exercise training improves retrograde SR, while the magnitude of this change correlated strongly with improvements in FMD and reductions in LF/HF ratio. Therefore, the impact of PE and exercise training on endothelial health may, at least partly, be related to retrograde shear rate.
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Affiliation(s)
- Ralph R Scholten
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands;
| | - Marc E A Spaanderman
- Research School GROW, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Daniel J Green
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Australia; and Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Maria T E Hopman
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Dick H J Thijssen
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
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57
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Thijssen DHJ, Atkinson CL, Ono K, Sprung VS, Spence AL, Pugh CJA, Green DJ. Sympathetic nervous system activation, arterial shear rate, and flow-mediated dilation. J Appl Physiol (1985) 2014; 116:1300-7. [DOI: 10.1152/japplphysiol.00110.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to examine the contribution of arterial shear to changes in flow-mediated dilation (FMD) during sympathetic nervous system (SNS) activation in healthy humans. Ten healthy men reported to our laboratory four times. Bilateral FMD, shear rate (SR), and catecholamines were examined before/after 10-min of −35-mmHg lower body negative pressure (LBNP10). On day 1, localized forearm heating (LBNP10+heat) was applied in one limb to abolish the increase in retrograde SR associated with LBNP. Day 2 involved unilateral cuff inflation to 75 mmHg around one limb to exaggerate the LBNP-induced increase retrograde SR (LBNP10+cuff). Tests were repeated on days 3 and 4, using 30-min interventions (i.e., LBNP30+heat and LBNP30+cuff). LBNP10 significantly increased epinephrine levels and retrograde SR and decreased FMD (all P < 0.05). LBNP10+heat prevented the increase in retrograde SR, whereas LBNP10+cuff further increased retrograde SR ( P < 0.05). Heating prevented the decrease in percent FMD (FMD%) after LBNP10 (interaction effect, P < 0.05), whereas cuffing did not significantly exaggerate the decrease in FMD% (interaction effect, P > 0.05). Prolongation of the LBNP stimulus for 30-min normalized retrograde SR, catecholamine levels, and FMD (all P > 0.05). Attenuation of retrograde SR during 30 min (LBNP30+heat) was associated with increased FMD% (interaction effects, P < 0.05), whereas increased retrograde SR (LBNP30+cuff) diminished FMD% (interaction effects, P < 0.05). These data suggest that LBNP-induced SNS stimulation decreases FMD, at least in part due to the impact of LBNP on arterial shear stress. Prolonged LBNP stimulation was not associated with changes in SR or FMD%. Our data support a role for changes in SR to the impact of SNS stimulation on FMD.
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Affiliation(s)
- Dick H. J. Thijssen
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom; and
- Department of Physiology, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Ceri L. Atkinson
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
| | - Kumiko Ono
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
| | - Victoria S. Sprung
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
| | - Angela L. Spence
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
| | - Christopher J. A. Pugh
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
| | - Daniel J. Green
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom; and
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58
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Ku J, McEvoy A, Pyke KE. Can a combination of handgrip exercise and prolonged forearm occlusion elicit a maximal brachial artery FMD response? Eur J Appl Physiol 2014; 114:1297-307. [DOI: 10.1007/s00421-014-2859-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 02/17/2014] [Indexed: 10/25/2022]
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59
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Green DJ, Dawson EA, Groenewoud HM, Jones H, Thijssen DH. Is Flow-Mediated Dilation Nitric Oxide Mediated? Hypertension 2014; 63:376-82. [DOI: 10.1161/hypertensionaha.113.02044] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Flow-mediated dilation (FMD) is a noninvasive index of endothelial function and vascular health in humans. Studies examining the role of nitric oxide (NO) are not conclusive. In this article, we quantified the contribution of NO in FMD of conduit arteries and explored the effect of the protocol (ie, distal cuff, ≈5-minute ischemia) and method of analysis (ie, automated and continuous edge detection) on the NO dependency of this test. A systematic review and 3-stage meta-analysis of published crossover studies that measured FMD under local infusion of saline or the NO synthase blocker
N
G
monomethyl-L-arginine (L-NMMA) was undertaken. Twenty studies met the inclusion criteria for stage 1 (374 individual comparisons). The meta-analyzed outcome was the difference in FMD between infusion of saline (ie, FMD
saline
) and NO synthase blocker (ie, FMD
L-NMMA
). Overall, FMD
saline
was 8.2% (95% confidence interval [CI], 6.8%–9.6%) compared with FMD
L-NMMA
of 3.7% (95% CI, 3.1%–4.3%;
P
<0.001). Stage 2 analysis focused on studies that used the most commonly adopted approach in healthy volunteers (ie, distal cuff placement, ≈5-minute occlusion), which similarly revealed a significant NO contribution to FMD (FMD
saline
, 6.5% [95% CI, 5.7%–7.3%]; FMD
L-NMMA
, 0.9% [95% CI, 0.5%–1.3%];
P
<0.001). Stage 3 meta-analyzed the studies that adopted the commonly adopted approach and automated, continuous method of analysis, which also revealed a significant contribution of NO to the FMD (FMD
saline
, 6.9% [95% CI, 6.0%–7.8%]; FMD
L-NMMA
, 2.4% [95% CI, 1.1%–3.7%];
P
<0.001). This comprehensive analysis demonstrates that FMD of conduit arteries in humans is, at least in part, mediated by NO.
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Affiliation(s)
- Daniel J. Green
- From the Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom (D.J.G., E.A.D., H.J., D.H.J.T.); School of Sports Science, Exercise and Health, The University of Western Australia, Crawley Perth, Western Australia (D.J.G.); and Departments of Health Evidence (H.M.M.G.) and Physiology (D.H.J.T.), Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ellen A. Dawson
- From the Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom (D.J.G., E.A.D., H.J., D.H.J.T.); School of Sports Science, Exercise and Health, The University of Western Australia, Crawley Perth, Western Australia (D.J.G.); and Departments of Health Evidence (H.M.M.G.) and Physiology (D.H.J.T.), Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hans M.M. Groenewoud
- From the Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom (D.J.G., E.A.D., H.J., D.H.J.T.); School of Sports Science, Exercise and Health, The University of Western Australia, Crawley Perth, Western Australia (D.J.G.); and Departments of Health Evidence (H.M.M.G.) and Physiology (D.H.J.T.), Radboud University Medical Center, Nijmegen, The Netherlands
| | - Helen Jones
- From the Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom (D.J.G., E.A.D., H.J., D.H.J.T.); School of Sports Science, Exercise and Health, The University of Western Australia, Crawley Perth, Western Australia (D.J.G.); and Departments of Health Evidence (H.M.M.G.) and Physiology (D.H.J.T.), Radboud University Medical Center, Nijmegen, The Netherlands
| | - Dick H.J. Thijssen
- From the Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom (D.J.G., E.A.D., H.J., D.H.J.T.); School of Sports Science, Exercise and Health, The University of Western Australia, Crawley Perth, Western Australia (D.J.G.); and Departments of Health Evidence (H.M.M.G.) and Physiology (D.H.J.T.), Radboud University Medical Center, Nijmegen, The Netherlands
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Chen Q, Wang J, Tian J, Tang X, Yu C, Marshall RJ, Chen D, Cao W, Zhan S, Lv J, Lee L, Hu Y. Association between ambient temperature and blood pressure and blood pressure regulators: 1831 hypertensive patients followed up for three years. PLoS One 2013; 8:e84522. [PMID: 24391962 PMCID: PMC3877276 DOI: 10.1371/journal.pone.0084522] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Accepted: 11/14/2013] [Indexed: 12/27/2022] Open
Abstract
Several studies have suggested an association between ambient air temperature and blood pressure. However, this has not been reliably confirmed by longitudinal studies. Also, whether the reaction to temperature stimulation is modified by other factors such as antihypertensive medication is rarely investigated. The present study explores the relationship between ambient temperature and blood pressure, without and with antihypertensive medication, in a study of 1,831 hypertensive patients followed up for three years, in two or four weekly check ups, accumulating 62,452 follow-up records. Both baseline and follow-up blood pressure showed an inverse association with ambient temperature, which explained 32.4% and 65.6% of variation of systolic blood pressure and diastolic blood pressure (P<0.05) respectively. The amplitude of individual blood pressure fluctuation with temperature throughout a year (a 29 degrees centigrade range) was 9.4/7.3 mmHg. Medication with angiotensin converting enzyme inhibitor benazepril attenuated the blood pressure fluctuation by 2.4/1.3 mmHg each year, though the inverse association of temperature and blood pressure remained. Gender, drinking behavior and body mass index were also found to modify the association between temperature and diastolic blood pressure. The results indicate that ambient temperature may negatively regulate blood pressure. Hypertensive patients should monitor and treat blood pressure more carefully in cold days, and it could be especially important for the males, thinner people and drinkers.
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Affiliation(s)
- Qing Chen
- Department of Hygienic Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, P. R. China
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Jinwei Wang
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Jun Tian
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Xun Tang
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Canqing Yu
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Roger J. Marshall
- Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand
| | - Dafang Chen
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Weihua Cao
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Siyan Zhan
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Jun Lv
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Liming Lee
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
| | - Yonghua Hu
- Department of Epidemiology & Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, P. R. China
- * E-mail:
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Cerebral hemodynamics and systemic endothelial function are already impaired in well-controlled type 2 diabetic patients, with short-term disease. PLoS One 2013; 8:e83287. [PMID: 24391751 PMCID: PMC3877017 DOI: 10.1371/journal.pone.0083287] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/11/2013] [Indexed: 01/22/2023] Open
Abstract
Objective Impaired cerebral vasomotor reactivity (VMR) and flow-mediated dilation (FMD) were found in selected subgroups of type 2 diabetes mellitus (T2DM) patients with long-term disease. Our study aimed to evaluate cerebral hemodynamics, systemic endothelial function and sympatho-vagal balance in a selected population of well-controlled T2DM patients with short-term disease and without cardiac autonomic neuropathy (CAN). Research Design and Methods Twenty-six T2DM patients with short-term (4.40±4.80 years) and well-controlled (HbA1C = 6.71±1.29%) disease, without any complications, treated with diet and/or metformin, were consecutively recruited. Eighteen controls, comparable by sex and age, were enrolled also. Results FMD and shear rate FMD were found to be reduced in T2DM subjects with short-term disease (8.5% SD 3.5 and 2.5 SD 1.3, respectively) compared to controls (15.4% SD 4.1 and 3.5 SD 1.4; p<.001 and p<.05). T2DM patients also displayed reduced VMR values than controls (39.4% SD 12.4 vs 51.7%, SD 15.5; p<.05). Sympatho-vagal balance was not different in T2DM patients compared to healthy subjects. FMD and shear rate FMD did not correlate with VMR in T2DM patients or in controls (p>.05). Conclusions In well-controlled T2DM patients with short-term disease cerebral hemodynamics and systemic endothelial function are altered while autonomic balance appeared to be preserved.
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Lewis NCS, Bailey DM, Dumanoir GR, Messinger L, Lucas SJE, Cotter JD, Donnelly J, McEneny J, Young IS, Stembridge M, Burgess KR, Basnet AS, Ainslie PN. Conduit artery structure and function in lowlanders and native highlanders: relationships with oxidative stress and role of sympathoexcitation. J Physiol 2013; 592:1009-24. [PMID: 24324004 DOI: 10.1113/jphysiol.2013.268615] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Research detailing the normal vascular adaptions to high altitude is minimal and often confounded by pathology (e.g., chronic mountain sickness) and methodological issues. We examined vascular function and structure in: (1) healthy lowlanders during acute hypoxia and prolonged (∼2 weeks) exposure to high altitude, and (2) high-altitude natives at 5050 m (highlanders). In 12 healthy lowlanders (aged 32 ± 7 years) and 12 highlanders (Sherpa; 33 ± 14 years) we assessed brachial endothelium-dependent flow-mediated dilatation (FMD), endothelium-independent dilatation (via glyceryl trinitrate; GTN), common carotid intima-media thickness (CIMT) and diameter (ultrasound), and arterial stiffness via pulse wave velocity (PWV; applanation tonometry). Cephalic venous biomarkers of free radical-mediated lipid peroxidation (lipid hydroperoxides, LOOH), nitrite (NO2-) and lipid soluble antioxidants were also obtained at rest. In lowlanders, measurements were performed at sea level (334 m) and between days 3-4 (acute high altitude) and 12-14 (chronic high altitude) following arrival to 5050 m. Highlanders were assessed once at 5050 m. Compared with sea level, acute high altitude reduced lowlanders' FMD (7.9 ± 0.4 vs. 6.8 ± 0.4%; P = 0.004) and GTN-induced dilatation (16.6 ± 0.9 vs. 14.5 ± 0.8%; P = 0.006), and raised central PWV (6.0 ± 0.2 vs. 6.6 ± 0.3 m s(-1); P = 0.001). These changes persisted at days 12-14, and after allometrically scaling FMD to adjust for altered baseline diameter. Compared to lowlanders at sea level and high altitude, highlanders had a lower carotid wall:lumen ratio (∼19%, P ≤ 0.04), attributable to a narrower CIMT and wider lumen. Although both LOOH and NO2- increased with high altitude in lowlanders, only LOOH correlated with the reduction in GTN-induced dilatation evident during acute (n = 11, r = -0.53) and chronic (n = 7, r = -0.69; P ≤ 0.01) exposure to 5050 m. In a follow-up, placebo-controlled experiment (n = 11 healthy lowlanders) conducted in a normobaric hypoxic chamber (inspired O2 fraction (F IO 2) = 0.11; 6 h), a sustained reduction in FMD was evident within 1 h of hypoxic exposure when compared to normoxic baseline (5.7 ± 1.6 vs. 8.0 ±1.3%; P < 0.01); this decline in FMD was largely reversed following α1-adrenoreceptor blockade. In conclusion, high-altitude exposure in lowlanders caused persistent impairment in vascular function, which was mediated partially via oxidative stress and sympathoexcitation. Although a lifetime of high-altitude exposure neither intensifies nor attenuates the impairments seen with short-term exposure, chronic high-altitude exposure appears to be associated with arterial remodelling.
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Affiliation(s)
- Nia C S Lewis
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan Campus, School of Health and Exercise Sciences 111 Health Science Centre 1088 Discovery Avenue, Kelowna, British Columbia, Canada.
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63
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Allen AP, Kennedy PJ, Cryan JF, Dinan TG, Clarke G. Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test. Neurosci Biobehav Rev 2013; 38:94-124. [PMID: 24239854 DOI: 10.1016/j.neubiorev.2013.11.005] [Citation(s) in RCA: 424] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 11/01/2013] [Accepted: 11/06/2013] [Indexed: 12/24/2022]
Abstract
Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.
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Affiliation(s)
- Andrew P Allen
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Psychiatry, University College Cork, Cork, Ireland
| | - Paul J Kennedy
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Psychiatry, University College Cork, Cork, Ireland
| | - John F Cryan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Timothy G Dinan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Psychiatry, University College Cork, Cork, Ireland
| | - Gerard Clarke
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Psychiatry, University College Cork, Cork, Ireland.
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64
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Dawson EA, Green DJ, Cable NT, Thijssen DHJ. Effects of acute exercise on flow-mediated dilatation in healthy humans. J Appl Physiol (1985) 2013; 115:1589-98. [PMID: 24030665 DOI: 10.1152/japplphysiol.00450.2013] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Although the effects of exercise training on vascular function have been well studied, less is known about the effects of acute exercise bouts. This synthesis summarizes and integrates knowledge derived from papers relating acute impacts of exercise on artery function, specifically endothelial function assessed by flow-mediated dilatation (FMD). We propose that an immediate decrease in FMD ("nadir") occurs soon after exercise cessation and that this is followed by a (supra)normalization response. The magnitude of the nadir and (supra)normalization and duration of this biphasic pattern of response appears to be influenced by numerous factors, including the nature of the exercise stimulus (e.g., type, duration, intensity), the subject population (e.g., trained vs. untrained), and various methodological factors. The impact of these factors on the biphasic pattern are most likely mediated through stimuli that underpin altered FMD postexercise, including shear and oxidative stress, changes in arterial diameter, and antioxidant status. We propose that a combination of these stimuli act synergistically to balance the vasomotor responses postexercise. Finally, we discuss the potential (clinical) relevance of the biphasic response after acute exercise, as the immediate nadir may represent an essential response for subsequent training-induced adaptations but may also represent a transient period of increased cardiovascular risk leading to the "exercise paradox."
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Affiliation(s)
- Ellen A Dawson
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom
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65
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Fairfax ST, Padilla J, Vianna LC, Holwerda SH, Davis MJ, Fadel PJ. Influence of spontaneously occurring bursts of muscle sympathetic nerve activity on conduit artery diameter. Am J Physiol Heart Circ Physiol 2013; 305:H867-74. [PMID: 23832696 DOI: 10.1152/ajpheart.00372.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Large increases in muscle sympathetic nerve activity (MSNA) can decrease the diameter of a conduit artery even in the presence of elevated blood pressure, suggesting that MSNA acts to regulate conduit artery tone. Whether this influence can be extrapolated to spontaneously occurring MSNA bursts has not been examined. Therefore, we tested the hypothesis that MSNA bursts decrease conduit artery diameter on a beat-by-beat basis during rest. Conduit artery responses were assessed in the brachial (BA), common femoral (CFA) and popliteal (PA) arteries to account for regional differences in vascular function. In 20 young men, MSNA, mean arterial pressure (MAP), conduit artery diameter, and shear rate (SR) were continuously measured during 20-min periods of supine rest. Spike-triggered averaging was used to characterize beat-by-beat changes in each variable for 15 cardiac cycles following all MSNA bursts, and a peak response was calculated. Diameter increased to a similar peak among the BA (+0.14 ± 0.02%), CFA (+0.17 ± 0.03%), and PA (+0.18 ± 0.03%) following MSNA bursts (all P < 0.05 vs. control). The diameter rise was positively associated with an increase in MAP in relation to increasing amplitude and consecutive numbers of MSNA bursts (P < 0.05). Such relationships were similar between arteries. SR changes following MSNA bursts were heterogeneous between arteries and did not appear to systematically alter diameter responses. Thus, in contrast to our hypothesis, spontaneously occurring MSNA bursts do not directly influence conduit arteries with local vasoconstriction or changes in shear, but rather induce a systemic pressor response that appears to passively increase conduit artery diameter.
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Affiliation(s)
- Seth T Fairfax
- Biomedical Sciences, University of Missouri, Columbia, Missouri
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66
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Paine NJ, Ring C, Bosch JA, McIntyre D, Veldhuijzen van Zanten JJCS. The effect of acute mental stress on limb vasodilation is unrelated to total peripheral resistance. Psychophysiology 2013; 50:680-90. [PMID: 23656692 DOI: 10.1111/psyp.12054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 03/26/2013] [Indexed: 01/01/2023]
Abstract
Mental stress can trigger myocardial infarction, with poor vascular responses to stress implicated as a pathway. Vascular stress reactivity can be assessed by different methods, such as total peripheral resistance (TPR) and forearm blood flow (FBF). Little is known about how these vascular assessments are linked. This was examined in two separate studies. Healthy men (Study 1: N = 29, Study 2: N = 23) completed rest and mental arithmetic (Study 1: 8 min, Study 2: 16 min). In both studies, heart rate, mean arterial pressure, and FBF increased in response to stress. In Study 1, no changes in TPR were seen, but Study 2 found stress-induced increases in TPR. FBF was not linked to TPR at any time (all ps > .05). It appears that limb vasculature and TPR responses to stress do not give the same information about impairments of the vasculature. These findings are relevant to the interpretation of prior research findings and the design of future studies on stress and vascular responses.
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Affiliation(s)
- Nicola J Paine
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UK, B15 2TT.
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67
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Szijgyarto IC, King TJ, Ku J, Poitras VJ, Gurd BJ, Pyke KE. The impact of acute mental stress on brachial artery flow-mediated dilation differs when shear stress is elevated by reactive hyperemia versus handgrip exercise. Appl Physiol Nutr Metab 2013; 38:498-506. [DOI: 10.1139/apnm-2012-0328] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acute mental stress can impair brachial artery (BA) flow-mediated dilation (FMD) in response to reactive hyperemia (RH) induced increases in shear stress. Handgrip exercise (HGEX) is emerging as a useful tool to increase shear stress for FMD assessment; however, the impact of acute mental stress on HGEX-FMD is unknown. The purpose of this study was to determine whether acute mental stress attenuates RH- and HGEX-induced BA-FMD to a similar extent. In 2 counterbalanced visits, 16 healthy males (19–27 years of age) performed RH-FMD or HGEX-FMD tests after a counting control task (prestress FMD) and a speech and arithmetic stress task (poststress FMD). BA diameter and mean blood velocity were assessed with echo and Doppler ultrasound, respectively. Shear stress was estimated using shear rate (SR = BA blood velocity/BA diameter). Mean arterial pressure (MAP), heart rate (HR), and salivary cortisol were used to assess stress reactivity. Results are expressed as mean ± SE. The stress task elevated MAP (Δ24.0 ± 2.6 mm Hg) and HR (Δ15.5 ± 1.9 beats·min–1), but not cortisol (prestress vs. poststress: 4.4 ± 0.7 nmol·L–1 vs. 4.7 ± 0.7 nmol·L–1; p = 0.625). There was no difference between the pre- and poststress SR stimulus for RH (p = 0.115) or HGEX (p = 0.664). RH-FMD decreased from 5.2% ± 0.6% prestress to 4.1% ± 0.5% poststress (p = 0.071); however, stress did not attenuate HGEX-FMD (prestress vs. poststress: 4.1% ± 0.6% vs. 5.3% ± 0.6%; p = 0.154). The pre- to poststress change in FMD was significantly different in the RH-FMD vs. the HGEX-FMD test (–1.1% ± 0.6% vs. +1.1% ± 0.8%; p = 0.015). In conclusion, acute mental stress appears to have a disparate impact on FMD stimulated by RH vs. HGEX induced increases in shear stress.
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Affiliation(s)
- Ingrid C. Szijgyarto
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Trevor J. King
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Jennifer Ku
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Veronica J. Poitras
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Brendon J. Gurd
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Kyra E. Pyke
- School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
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68
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Poitras VJ, Pyke KE. The impact of acute mental stress on vascular endothelial function: evidence, mechanisms and importance. Int J Psychophysiol 2013; 88:124-35. [PMID: 23562766 DOI: 10.1016/j.ijpsycho.2013.03.019] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/21/2013] [Accepted: 03/26/2013] [Indexed: 01/23/2023]
Abstract
Cardiovascular disease is a principle cause of morbidity and mortality worldwide, and it has a complex etiology that involves lifestyle factors such as psychosocial stress. Recent evidence suggests that temporary impairments in vascular endothelial cell function may contribute to the relationship between stress and cardiovascular disease. Indeed, impaired endothelial function has been observed to occur transiently (lasting up to 1.5h) following mental stress, and such periods of impairment could accumulate to become clinically relevant over the long term. The finding of acute stress induced endothelial dysfunction is not universal however, and both physiological (e.g. sympathetic nervous system and hypothalamic-pituitary-adrenal axis reactivity), and methodological factors contribute to the conflicting results. A clear understanding of the interaction between stress response activation and endothelial function is critical to elucidating the complexities of the relationship between psychosocial stress and cardiovascular disease. Therefore, the purpose of this review is: 1) to briefly describe the importance of vascular endothelial function and how it is assessed, 2) to review the literature investigating the impact of acute mental stress on endothelial function in humans, identifying factors that may explain contradictory results, and 3) to summarize our current understanding of the mechanisms that may mediate an acute mental stress-endothelial function interaction.
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Affiliation(s)
- Veronica J Poitras
- Queen's University School of Kinesiology and Health Studies, 28 Division St. Kingston, Ontario, Canada
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69
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Silverthorn DU, Michael J. Cold stress and the cold pressor test. ADVANCES IN PHYSIOLOGY EDUCATION 2013; 37:93-6. [PMID: 23471256 DOI: 10.1152/advan.00002.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Temperature and other environmental stressors are known to affect blood pressure and heart rate. In this activity, students perform the cold pressor test, demonstrating increased blood pressure during a 1- to 2-min immersion of one hand in ice water. The cold pressor test is used clinically to evaluate autonomic and left ventricular function. This activity is easily adapted to an inquiry format that asks students to go to the scientific literature to learn about the test and then design a protocol for carrying out the test in classmates. The data collected are ideal for teaching graphical presentation of data and statistical analysis.
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Affiliation(s)
- Dee U Silverthorn
- Section of Integrative Biology, University of Texas, Austin, TX 78712, USA.
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70
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GREEN DANIELJ, ROWLEY NICOLA, SPENCE ANGELA, CARTER HOWARD, WHYTE GREG, GEORGE KEITH, NAYLOR LOUISEH, CABLE NTIMOTHY, DAWSON ELLENA, J. THIJSSEN DICKH. Why Isn’t Flow-Mediated Dilation Enhanced in Athletes? Med Sci Sports Exerc 2013; 45:75-82. [DOI: 10.1249/mss.0b013e318269affe] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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71
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Carter HH, Dawson EA, Birk GK, Spence AL, Naylor LH, Cable NT, Thijssen DH, Green DJ. Effect of SR Manipulation on Conduit Artery Dilation in Humans. Hypertension 2013; 61:143-50. [DOI: 10.1161/hypertensionaha.112.197277] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The impact of manipulating shear stress on conduit artery vasodilation has not been comprehensively described in vivo. We hypothesized that manipulation of SR through the brachial and radial arteries would be associated with corresponding changes in diameter. We performed a series of studies involving the following: (1) leg cycle exercise at increasing intensities (≈70 and 85% maximum heart rate [HRmax]) with simultaneous bilateral measurement of SR in the radial arteries; (2) leg cycle exercise for 30 minutes at 80% HRmax with simultaneous bilateral measurement of velocity and diameter in the brachial arteries; and (3) bilateral forearm heating for 30 minutes with simultaneous bilateral measurement of brachial artery diameter and blood velocity. Cycling and forearm heating interventions were performed in the presence of unilateral cuff inflation throughout the experiment, or starting during the intervention (15 minutes), to manipulate SR responses. Cuff placement was associated with lower radial artery SR responses (cuffed versus uncuffed, 248±49 versus 349±105 L/s 85% HRmax;
P
<0.01), and diameter responses were similarly attenuated (2.45±0.30 versus 2.78±0.20 mm 85% HRmax;
P
<0.05). Exercise performed at 80% HRmax in the presence of unilateral cuff inflation also reduced brachial artery SR (cuffed versus uncuffed; 258±107 versus 454±157 L/s;
P
<0.01) and diameter (3.96±0.39 versus 4.20±0.45 mm). Finally, cuff inflation decreased the impact of forearm heating on brachial SR (cuffed versus uncuffed; 262±97 versus 440±106 L/s;
P
<0.01) and diameter (4.35±0.54 versus 4.87±0.47 mm;
P
<0.05). Similar significant differences between the cuffed and uncuffed limbs in SR and diameter were observed when cuff inflation occurred during exercise or heating. Our findings strongly implicate SR as an important stimulus to increase conduit artery diameter in humans.
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Affiliation(s)
- Howard H. Carter
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Ellen A. Dawson
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Gurpreet K. Birk
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Angela L. Spence
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Louise H. Naylor
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - N. Timothy Cable
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Dick H.J. Thijssen
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
| | - Daniel J. Green
- From the School of Sport Science, Exercise, and Health, University of Western Australia, Crawley, Western Australia, Australia (H.H.C., A.L.S., L.H.N., D.J.G.); Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom (E.A.D., G.K.B., N.T.C., D.H.J.T., D.J.G.); and Department of Physiology, Radboud University Nijmegen Medical Centre, Radboud, the Netherlands (D.H.J.T.)
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72
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Wagner JA, Tennen H, Finan PH, White WB, Burg MM, Ghuman N. Lifetime History of Depression, Type 2 Diabetes, and Endothelial Reactivity to Acute Stress in Postmenopausal Women. Int J Behav Med 2011; 19:503-11. [DOI: 10.1007/s12529-011-9190-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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73
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Jazuli F, Pyke KE. The impact of baseline artery diameter on flow-mediated vasodilation: a comparison of brachial and radial artery responses to matched levels of shear stress. Am J Physiol Heart Circ Physiol 2011; 301:H1667-77. [DOI: 10.1152/ajpheart.00487.2011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An inverse relationship between baseline artery diameter (BAD) and flow-mediated vasodilation (FMD) has been identified using reactive hyperemia (RH) to create a shear stress (SS) stimulus in human conduit arteries. However, RH creates a SS stimulus that is inversely related to BAD. The purpose of this study was to compare FMD in response to matched levels of SS in two differently sized upper limb arteries [brachial (BA) and radial (RA) artery]. With the use of exercise, three distinct, shear rate (SR) stimuli were created (SR = blood velocity/vessel diameter; estimate of SS) in the RA and BA. Artery diameter and mean blood velocity were assessed with echo and Doppler ultrasound in 15 healthy male subjects (19–25 yr). Data are means ± SE. Subjects performed 6 min of adductor pollicis and handgrip exercise to increase SR in the RA and BA, respectively. Exercise intensity was modulated to achieve uniformity in SR between arteries. The three distinct SR levels were as follows: steady-state exercise 39.8 ± 0.6, 57.3 ± 0.7, and 72.4 ± 1.2 s−1 ( P < 0.001). %FMD and AbsFMD (mm) at the end of exercise were greater in the RA vs. the BA at each shear level [at the highest level: RA = 15.7 ± 1.5%, BA = 5.4 ± 0.8% ( P < 0.001)]. The mean slope of the within-subject SR-%FMD regression line was greater in the RA (RA = 0.33 ± 0.04, BA = 0.13 ± 0.02, P < 0.001), and a strong within-subjects relationship between %FMD and SR was observed in both arteries (RA: r2 = 0.92 ± 0.02; BA: r2 = 0.90 ± 0.03). Within the RA, there was a significant relationship between baseline diameter and %FMD; however, this relationship was not present in the BA (RA: r2 = 0.76, P < 0.001; BA: r2 = 0.03, P = 0.541). These findings suggest that the response to SS is not uniform across differently sized vessels, which is in agreement with previous studies.
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Affiliation(s)
- F. Jazuli
- Queen's University, Kingston, Ontario, Canada
| | - K. E. Pyke
- Queen's University, Kingston, Ontario, Canada
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74
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Frances MF, Goswami R, Rachinsky M, Craen R, Kiviniemi AM, Fleischhauer A, Steinback CD, Zamir M, Shoemaker JK. Adrenergic and myogenic regulation of viscoelasticity in the vascular bed of the human forearm. Exp Physiol 2011; 96:1129-37. [DOI: 10.1113/expphysiol.2011.059188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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75
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Kaplon RE, Walker AE, Seals DR. Plasma norepinephrine is an independent predictor of vascular endothelial function with aging in healthy women. J Appl Physiol (1985) 2011; 111:1416-21. [PMID: 21903879 DOI: 10.1152/japplphysiol.00721.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We tested the hypothesis that reductions in vascular endothelial function (endothelium-dependent dilation, EDD) with age are related to increases in sympathetic activity. Among 314 healthy men and women, age was inversely related to brachial artery flow-mediated dilation (FMD) (r = -0.30, P < 0.001), a measure of EDD, and positively related to plasma norepinephrine concentrations (PNE), a marker of sympathetic activity (r = 0.49, P < 0.001). Brachial FMD was inversely related to PNE in all subjects (r = -0.25, P < 0.001) and in men (n = 187, r = -0.17, P = 0.02) and women (n = 127, r = -0.37, P < 0.001) separately. After controlling for PNE (multiple regression analysis), brachial FMD remained significantly related to age in all subjects (r = -0.20, P < 0.001) and in men (r = -0.23, P < 0.01), but not women (r = -0.16, P = 0.06). Consistent with this, brachial FMD remained significantly related to PNE when controlling for age (r = -0.24, P < 0.01) and menopause status (r = -0.24, P < 0.01) in women. Indeed, PNE was the strongest independent correlate of brachial FMD in women after controlling for conventional cardiovascular disease risk factors (r = -0.22, P = 0.01). This relation persisted in a subset of women (n = 113) after further accounting for the effects of plasma oxidized low-density lipoprotein (P < 0.05), a circulating marker of oxidative stress. Endothelium-independent dilation was not related to age in either men or women (P > 0.05). These results provide the first evidence that EDD is inversely related to sympathetic activity, as assessed by PNE, among healthy adults varying in age. In particular, our findings suggest that sympathetic nervous system activity may be a key factor involved in the modulation of vascular endothelial function with aging in women.
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Affiliation(s)
- Rachelle E Kaplon
- Dept. of Integrative Physiology, Univ. of Colorado at Boulder, Boulder, CO 80309, USA
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76
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Gibbs BB, Dobrosielski DA, Lima M, Bonekamp S, Stewart KJ, Clark JM. The association of arterial shear and flow-mediated dilation in diabetes. Vasc Med 2011; 16:267-74. [PMID: 21708874 PMCID: PMC4397901 DOI: 10.1177/1358863x11411361] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
While adjusting flow-mediated dilation (FMD), a measure of vascular function, for shear rate may be important when evaluating endothelial-dependent vasodilation, the relationship of FMD with shear rate in study populations with cardiovascular risk factors is unclear. We aimed to investigate the association of four measures of shear rate (peak shear rate (SR(peak)) and shear rate area under the curve through 30 seconds (SR(AUC 0-30)), 60 seconds (SR(AUC 0-60)), and time to peak dilation (SR(AUC 0-ttp))) with FMD in 50 study subjects with type 2 diabetes and mild hypertension undergoing baseline FMD testing for an exercise intervention trial. Associations among measures of shear rate and FMD were evaluated using Pearson's correlations and R(2). The four measures of shear rate were highly correlated within subjects, with Pearson's correlations ranging from 0.783 (p < 0.001) to 0.972 (p < 0.001). FMD was associated with each measure of shear rate, having a correlation of 0.576 (p < 0.001) with SR(AUC 0-30), 0.529 (p < 0.001) with SR(AUC 0-60), and 0.512 (p < 0.001) with SR(peak). Nine of 50 subjects (18%) did not dilate following the shear stimulus. Among the 41 responders, FMD had a correlation of 0.517 (p < 0.001) with SR(AUC 0-ttp) and similar correlations to those found in the full sample for SR(AUC 0-30), SR(AUC 0-60), and SR(peak). In conclusion, shear rate appears to explain up to a third of between-person variability in FMD response and our results support the reporting of shear rate and FMD with and without adjustment for shear rate in similar clinical populations with CVD risk factors.
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Affiliation(s)
- Bethany Barone Gibbs
- Department of Epidemiology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
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77
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Rooks CR, McCully KK, Dishman RK. Acute exercise improves endothelial function despite increasing vascular resistance during stress in smokers and nonsmokers. Psychophysiology 2011; 48:1299-308. [PMID: 21457274 DOI: 10.1111/j.1469-8986.2011.01194.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The present study examined the effect of acute exercise on flow mediated dilation (FMD) and reactivity to neurovascular challenges among female smokers and nonsmokers. FMD was determined by arterial diameter, velocity, and blood flow measured by Doppler ultrasonography after forearm occlusion. Those measures and blood pressure and heart rate were also assessed in response to forehead cold and the Stroop Color-Word Conflict Test (CWT) before and after 30 min of rest or an acute bout of cycling exercise (∼50% VO₂ peak). Baseline FMD and stress responses were not different between smokers and nonsmokers. Compared to passive rest, exercise increased FMD and decreased arterial velocity and blood flow responses during the Stroop CWT and forehead cold in both groups. Overall, acute exercise improved endothelial function among smokers and nonsmokers despite increasing vascular resistance and reducing limb blood flow during neurovascular stress.
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Affiliation(s)
- Cherie R Rooks
- Department of Kinesiology, University of Georgia, Athens, Georgia 30322, USA.
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78
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Impact of blood pressure cuff inflation rates on flow-mediated dilatation and contralateral arm response. J Hum Hypertens 2011; 26:35-40. [PMID: 21248779 DOI: 10.1038/jhh.2010.128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Flow-mediated dilatation (FMD) is widely used as an index of nitric oxide-mediated vasodilator function, yet its methodology has not been well established. Previous research indicates that a rapid inflation of a blood pressure cuff evokes systemic vasoconstriction, as it was observed even on non-occluded contralateral arm. This would potentially contribute to the variability of FMD readings and complicate the emerging evidence that non-occluded contralateral arm fingertip temperature responses during the FMD procedure may be an indicator of the presence of coronary artery disease. To test the hypotheses that rapid inflation of a blood pressure cuff could reduce FMD values and influence contralateral vasodilatory states, 33 apparently healthy adults (18 males and 15 females, 29±6 years) were studied in two randomized FMD trials. The blood flow-occluding cuff was inflated rapidly (<1 s) in one trial or slowly over 10 s in the other trial. Arterial diameter, fingertip temperature and infrared thermography were obtained throughout each session. FMD values were not different between the rapid and slow cuff inflation trials (5.9±0.6 vs 5.9±0.4%). There were no differences in reactive hyperaemia (6.4±1.6 vs 6.2±1.7 AU), shear stress (80±20 vs 77±17 dyn cm(-2)) and fingertip temperature rebound (TR; 1.8±1.2 vs 1.9±1.0 °C) between the rapid and slow inflation. Changes in finger temperature on the contralateral (non-occluded) arm were positively associated with those on the occluded arm (r=0.26 to 0.61, P<0.05). We concluded that rates of inflating a blood pressure cuff do not affect FMD and TR response, and that neurovascular-induced vasodilatation of the contralateral arm was not observed regardless of cuff inflation rates.
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79
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Pyke KE, Jazuli F. Impact of repeated increases in shear stress via reactive hyperemia and handgrip exercise: no evidence of systematic changes in brachial artery FMD. Am J Physiol Heart Circ Physiol 2010; 300:H1078-89. [PMID: 21186268 DOI: 10.1152/ajpheart.00736.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Reactive hyperemia (RH) creates an uncontrolled, transient increase in brachial artery (BA) shear stress (SS) for flow-mediated dilation (FMD) assessment. In contrast, handgrip exercise (HGEX) can create similar, sustained SS increases over repeated trials. The purpose of this study was to examine the impact of repeated SS elevation via RH or HGEX and the relationship between RH and HGEX %FMD. BA diameter and blood velocity were assessed with echo and Doppler ultrasound in 20 healthy subjects. Visit A consisted of four 6-min HGEX trials (HGEX trials 1-4) at the intensity required to achieve a shear rate (SR = mean blood velocity/BA diameter; an estimate of SS) of 65 s(-1). Visit B consisted of four RH trials (RH trials 1-4). The RH SR area under the curve (AUC) was higher in trial 1 versus trial 3 and trial 4 (P = 0.019 and 0.047). The HGEX mean SR was similar across trials (mean SR = 66.1 ± 5.8 s(-1), P = 0.152). There were no differences in %FMD across trials or tests (RH trial 1: 6.9 ± 3.5%, trial 2: 6.9 ± 2.3%, trial 3: 7.1 ± 3.5%, and trial 4: 7.0 ± 2.8%; HGEX trial 1: 7.3 ± 3.6%, trial 2: 7.0 ± 3.6%, trial 3: 6.5 ± 3.5%, and trial 4: 6.8 ± 2.9%, P = 0.913). No relationship between subject's RH %FMD and HGEX %FMD was detected (r(2) = 0.12, P = 0.137). However, with response normalization, a relationship emerged (RH %FMD/SR AUC vs. HGEX %FMD/mean SR, r(2) = 0.44, P = 0.002). In conclusion, with repeat trials, there were no systematic changes in RH or HGEX %FMD. The relationship between normalized RH and HGEX %FMD suggests that endothelial responses to different SS profiles provide related information regarding endothelial function.
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Affiliation(s)
- K E Pyke
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada.
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80
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Thijssen DHJ, Black MA, Pyke KE, Padilla J, Atkinson G, Harris RA, Parker B, Widlansky ME, Tschakovsky ME, Green DJ. Assessment of flow-mediated dilation in humans: a methodological and physiological guideline. Am J Physiol Heart Circ Physiol 2010; 300:H2-12. [PMID: 20952670 DOI: 10.1152/ajpheart.00471.2010] [Citation(s) in RCA: 1048] [Impact Index Per Article: 74.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endothelial dysfunction is now considered an important early event in the development of atherosclerosis, which precedes gross morphological signs and clinical symptoms. The assessment of flow-mediated dilation (FMD) was introduced almost 20 years ago as a noninvasive approach to examine vasodilator function in vivo. FMD is widely believed to reflect endothelium-dependent and largely nitric oxide-mediated arterial function and has been used as a surrogate marker of vascular health. This noninvasive technique has been used to compare groups of subjects and to evaluate the impact of interventions within individuals. Despite its widespread adoption, there is considerable variability between studies with respect to the protocols applied, methods of analysis, and interpretation of results. Moreover, differences in methodological approaches have important impacts on the response magnitude, can result in spurious data interpretation, and limit the comparability of outcomes between studies. This review results from a collegial discussion between physiologists with the purpose of developing considered guidelines. The contributors represent several distinct research groups that have independently worked to advance the evidence base for improvement of the technical approaches to FMD measurement and analysis. The outcome is a series of recommendations on the basis of review and critical appraisal of recent physiological studies, pertaining to the most appropriate methods to assess FMD in humans.
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Affiliation(s)
- Dick H J Thijssen
- Research Inst. for Sport and Exercise Science, Henry Cotton Campus, Liverpool John Moores Univ., 15-21 Webster St., Liverpool, L3 2ET, UK.
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81
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Jones H, Green DJ, George KP, Black MA, Atkinson G. Evidence for a greater elevation in vascular shear stress after morning exercise. Med Sci Sports Exerc 2010; 41:1188-93. [PMID: 19461550 DOI: 10.1249/mss.0b013e318195109c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION The vascular endothelium plays an important role in the maintenance of vascular health and the modulation of vascular tone and blood pressure. Recently, it has been demonstrated that blood pressure reactivity to physical activity is greater in the morning, and possibly, diurnal variation in vascular function may also be evident. The aim of this study was to assess vascular responses after exercise at different times of day. METHODS After 45 min of supine rest, 12 male normotensives completed a 30-min bout of cycling at 70% peak oxygen uptake beginning on separate days at 0800 and 1600 h. Edge detection and wall tracking of high-resolution arterial B-mode ultrasound images combined with synchronized Doppler waveform analysis were used to measure brachial and femoral conduit artery diameter and to calculate blood flow and shear rate. Measurements were recorded before and 20 min after exercise. RESULTS At 5 min after exercise, the mean +/- SE brachial shear rate was 72 +/- 21 arbitrary unit (AU) higher in the morning compared with the afternoon (P = 0.05), but this was not compensated for by enlargement of arterial diameter (P = 0.59). No diurnal variation was observed in the femoral artery measurements. CONCLUSION Diurnal difference in conduit artery regulatory control manifests as an elevated intravascular shear stress after morning exercise. Potentially, higher postexercise shear rate in the morning in at-risk individuals could contribute to the elevated cardiovascular risk evident in the postwaking hours.
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Affiliation(s)
- Helen Jones
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK.
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82
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Weissgerber TL, Davies GAL, Tschakovsky ME. Low flow-mediated constriction occurs in the radial but not the brachial artery in healthy pregnant and nonpregnant women. J Appl Physiol (1985) 2010; 108:1097-105. [PMID: 20185630 DOI: 10.1152/japplphysiol.00815.2009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Radial artery diameter decreases when a wrist cuff is inflated to stop blood flow to distal tissue. This phenomenon, referred to as low flow-mediated vasoconstriction (L-FMC), was proposed as a vascular function test. Recommendations that L-FMC be measured concurrently with flow-mediated dilation (FMD) were based on radial artery data. However, cardiovascular disease prediction studies traditionally measure brachial artery FMD. Therefore, studies should determine whether L-FMC occurs in the brachial artery. The hypothesis that reduced shear causes L-FMC has not been tested. Brachial and radial artery L-FMC and FMD were assessed in active nonpregnant (n=17), inactive nonpregnant (n=10), active pregnant (n=15, 34.1+/-1.2 wk gestation), and inactive pregnant (n=8, 34.2+/-2.2 wk gestation) women. Radial artery diameter decreased significantly during occlusion in all groups (nonpregnant, -4.4+/-4.2%; pregnant, -6.4+/-3.2%). Brachial artery diameter did not change in active and inactive nonpregnant, and inactive pregnant women; however, the small decrease in active pregnant women was significant. Occlusion decreased shear rate in both arteries, yet L-FMC only occurred in the radial artery. Radial artery L-FMC was not correlated with the reduction in shear rate. L-FMC occurs in the radial but not the brachial artery and is not related to changes in shear rate. Positive correlations between L-FMC (negative values) and FMD (positive values) suggest that radial artery FMD may be reduced among women who experience greater L-FMC. Studies should clarify the underlying stimulus and mechanisms regulating L-FMC, and test the hypothesis that endothelial dysfunction is manifested as enhanced brachial artery L-FMC, but attenuated radial artery L-FMC.
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Affiliation(s)
- Tracey L Weissgerber
- Department of Obstetrics, Gynecology, and Reproductive Science, Magee Women's Research Institute, 204 Craft Ave., Pittsburgh, PA 15213, USA.
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83
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Parker BA, Trehearn TL, Meendering JR. Pick your Poiseuille: normalizing the shear stimulus in studies of flow-mediated dilation. J Appl Physiol (1985) 2009; 107:1357-9. [DOI: 10.1152/japplphysiol.91302.2009] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Beth A. Parker
- Department of Preventive Cardiology, Hartford Hospital, Hartford, Connecticut; and
| | - Tamra L. Trehearn
- Department of Health, Physical Education, and Recreation, University of Nebraska Omaha, Omaha, Nebraska
| | - Jessica R. Meendering
- Department of Health, Physical Education, and Recreation, University of Nebraska Omaha, Omaha, Nebraska
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Black MA, Cable NT, Thijssen DHJ, Green DJ. Impact of age, sex, and exercise on brachial artery flow-mediated dilatation. Am J Physiol Heart Circ Physiol 2009; 297:H1109-16. [PMID: 19633208 DOI: 10.1152/ajpheart.00226.2009] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Flow-mediated dilatation (%FMD), an index of nitric oxide (NO)-mediated vasodilator function, is regarded as a surrogate marker of cardiovascular disease. Aging is associated with endothelial dysfunction, but underlying sex-related differences may exist and the effects of fitness and exercise on endothelial dysfunction in men (M) and women (W) are poorly understood. We compared %FMD of the brachial artery in 18 young [Y, 26 +/- 1 yr; 9 M and 9 W], 12 older fit (OF, 57 +/- 2 yr; 6 M and 6 W), and 16 older sedentary (OS, 59 +/- 2 yr; 8 M and 8 W) subjects. Glyceryl trinitrate (GTN) administration was used to assess endothelium-independent vasodilatation, and the FMD-to-GTN ratio was calculated to characterize NO dilator function in the context of smooth muscle cell sensitivity. Brachial %FMD in Y (7.1 +/- 0.8%) was significantly higher compared with OS (4.8 +/- 0.7%, P < 0.05), but not OF (6.4 +/- 0.7%). Differences between Y and OS subjects were due primarily to lower FMD in the OS women (4.3 +/- 0.6%). OS women exhibited significantly lower FMD-to-GTN ratios compared with Y (P < 0.05) and OF women (P < 0.05), whereas these differences were not apparent in men. Exercise training improved brachial artery NO dilator function (FMD-to-GTN ratio) after 24 wk (P < 0.05) in OS women, but not men. These findings indicate that maintaining a high level of fitness, or undertaking exercise training, prevents the age-related decline in the brachial artery vasodilator function evident in women. In OS men, who had relatively preserved NO dilator function, no training adaptations were observed. This study has potential implications for the prevention of conduit artery endothelial dysfunction in men and women.
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Affiliation(s)
- Mark A Black
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, L3 2ET, United Kingdom.
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85
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Thijssen DH, Dawson EA, Tinken TM, Cable NT, Green DJ. Retrograde Flow and Shear Rate Acutely Impair Endothelial Function in Humans. Hypertension 2009; 53:986-92. [DOI: 10.1161/hypertensionaha.109.131508] [Citation(s) in RCA: 225] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Dick H.J. Thijssen
- From the Research Institute for Sport and Exercise Science (D.H.J.T., E.A.D., T.M.T., N.T.C., D.J.G.), Liverpool John Moores University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the School of Sport Science (D.J.G.), Exercise and Health, University of Western Australia, Crawley, Western Australia, Australia
| | - Ellen A. Dawson
- From the Research Institute for Sport and Exercise Science (D.H.J.T., E.A.D., T.M.T., N.T.C., D.J.G.), Liverpool John Moores University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the School of Sport Science (D.J.G.), Exercise and Health, University of Western Australia, Crawley, Western Australia, Australia
| | - Toni M. Tinken
- From the Research Institute for Sport and Exercise Science (D.H.J.T., E.A.D., T.M.T., N.T.C., D.J.G.), Liverpool John Moores University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the School of Sport Science (D.J.G.), Exercise and Health, University of Western Australia, Crawley, Western Australia, Australia
| | - N. Timothy Cable
- From the Research Institute for Sport and Exercise Science (D.H.J.T., E.A.D., T.M.T., N.T.C., D.J.G.), Liverpool John Moores University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the School of Sport Science (D.J.G.), Exercise and Health, University of Western Australia, Crawley, Western Australia, Australia
| | - Daniel J. Green
- From the Research Institute for Sport and Exercise Science (D.H.J.T., E.A.D., T.M.T., N.T.C., D.J.G.), Liverpool John Moores University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the School of Sport Science (D.J.G.), Exercise and Health, University of Western Australia, Crawley, Western Australia, Australia
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86
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Central sympathetic overactivity: maladies and mechanisms. Auton Neurosci 2009; 148:5-15. [PMID: 19268634 DOI: 10.1016/j.autneu.2009.02.003] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 02/06/2009] [Accepted: 02/10/2009] [Indexed: 12/20/2022]
Abstract
There is growing evidence to suggest that many disease states are accompanied by chronic elevations in sympathetic nerve activity. The present review will specifically focus on central sympathetic overactivity and highlight three main areas of interest: 1) the pathological consequences of excessive sympathetic nerve activity; 2) the potential role of centrally derived nitric oxide in the genesis of neural dysregulation in disease; and 3) the promise of several novel therapeutic strategies targeting central sympathetic overactivity. The findings from both animal and human studies will be discussed and integrated in an attempt to provide a concise update on current work and ideas in these important areas.
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87
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Thijssen DHJ, Bullens LM, van Bemmel MM, Dawson EA, Hopkins N, Tinken TM, Black MA, Hopman MTE, Cable NT, Green DJ. Does arterial shear explain the magnitude of flow-mediated dilation?: a comparison between young and older humans. Am J Physiol Heart Circ Physiol 2008; 296:H57-64. [PMID: 19028795 DOI: 10.1152/ajpheart.00980.2008] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Flow-mediated dilatation (FMD) has become a commonly applied approach for the assessment of vascular function and health in humans. Recent studies emphasize the importance of normalizing the magnitude of FMD to its apparent eliciting stimulus, the postdeflation arterial shear. However, the relationship between shear stress and the magnitude of FMD may differ between groups. The aim of this study was to examine the relationship between the brachial FMD and four different indexes of postdeflation shear rate (SR) in healthy children (n = 51, 10 +/- 1 yr) and young (n = 57, 27 +/- 6 yr) and older (n = 27, 58 +/- 4 yr) adults. SR was calculated from deflation (time 0) until 9 s (peak), 30 s (0-30), 60 s (0-60), or until the time-to-peak diameter in each individual (0-ttp). Edge detection and wall tracking of high resolution B-mode arterial ultrasound images were used to calculate the conduit artery diameter. In young adults, the brachial artery FMD demonstrated a significant correlation with the area under the SR curve (SR(AUC)) 0-30 s (r(2) = 0.12, P = 0.009), 0-60 s (r(2) = 0.14, P = 0.005), and 0-ttp (r(2) = 0.14, P = 0.005) but not for the peak SR(AUC) 0-9 s (r(2) = 0.04, P = 0.12). In children and older adults, the magnitude of the brachial artery FMD did not correlate with any of the four SR(AUC) stimuli. These findings suggest that in young subjects, postdeflation SR(AUC) correlates moderately with the magnitude of the FMD response. However, the relationship between FMD and postdeflation shear appears to be age dependent, with less evidence for an association in younger and older subjects. Therefore, we support presenting SR(AUC) stimuli but not normalizing FMD responses for the SR(AUC) when using this technique.
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Affiliation(s)
- Dick H J Thijssen
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom.
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88
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Thijssen DHJ, van Bemmel MM, Bullens LM, Dawson EA, Hopkins ND, Tinken TM, Black MA, Hopman MTE, Cable NT, Green DJ. The impact of baseline diameter on flow-mediated dilation differs in young and older humans. Am J Physiol Heart Circ Physiol 2008; 295:H1594-8. [PMID: 18708443 DOI: 10.1152/ajpheart.00669.2008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Flow-mediated dilation (FMD) has become a commonly applied approach for the assessment of vascular function and health, but methods used to calculate FMD differ between studies. For example, the baseline diameter used as a benchmark is sometimes assessed before cuff inflation, whereas others use the diameter during cuff inflation. Therefore, we compared the brachial artery diameter before and during cuff inflation and calculated the resulting FMD in healthy children (n=45; 10+/-1 yr), adults (n=31; 28+/-6 yr), and older subjects (n=22; 58+/-5 yr). Brachial artery FMD was examined after 5 min of distal ischemia. Diameter was determined from either 30 s before cuff inflation or from the last 30 s during cuff inflation. Edge detection and wall tracking of high resolution B-mode arterial ultrasound images was used to calculate conduit artery diameter. Brachial artery diameter during cuff inflation was significantly larger than before inflation in children (P=0.02) and adults (P<0.001) but not in older subjects (P=0.59). Accordingly, FMD values significantly differed in children (11.2+/-5.1% vs. 9.4+/-5.2%; P=0.02) and adults (7.3+/-3.2% vs. 4.6+/-3.3%; P<0.001) but not in older subjects (6.3+/-3.4% vs. 6.0+/-4.2%; P=0.77). When the diameter before cuff inflation was used, an age-dependent decline was evident in FMD, whereas FMD calculated using the diameter during inflation was associated with higher FMD values in older than younger adults. In summary, the inflation of the cuff significantly increases brachial artery diameter, which results in a lower FMD response. This effect was found to be age dependent, which emphasizes the importance of using appropriate methodology to calculate the FMD.
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Affiliation(s)
- Dick H J Thijssen
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom.
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89
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Salzer DA, Medeiros PJ, Craen R, Shoemaker JK. Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1181-7. [PMID: 18685062 DOI: 10.1152/ajpregu.90333.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this investigation was to assess the interactive influence of sympathetic activation and supplemental nitric oxide (NO) on brachial artery distensibility vs. its diameter. It was hypothesized that 1) sympathetic activation and NO competitively impact muscular conduit artery (brachial artery) mechanics, and 2) neurogenic constrictor input affects conduit vessel stiffness independently of outright changes in conduit vessel diastolic diameter. Lower body negative pressure (LBNP) and a cold pressor stress (CPT) were used to study the changes in conduit vessel mechanics when the increased sympathetic outflow occurred with and without changes in heart rate (LBNP -40 vs. -15 mmHg) and blood pressure (CPT vs. LBNP). These maneuvers were performed in the absence and presence of nitroglycerin. Neither LBNP nor CPT altered brachial artery diastolic diameter; however, distensibility was reduced by 25 to 54% in each reflex (all P < 0.05). This impact of sympathetic activation on brachial artery distensibility was not altered by nitroglycerin supplementation (21-54%; P < 0.05), although baseline diameter was increased by the exogenous NO (P < 0.05). The results indicate that sympathetic excitation can reduce the distensibility of the brachial artery independently of concurrent changes in diastolic diameter, heart rate, and blood pressure. However, exogenous NO did not minimize or reverse brachial stiffening during sympathetic activation. Therefore, sympathetic outflow appears to impact the stiffness of this conduit vessel rather than its diastolic diameter or, by inference, its local resistance to flow.
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Affiliation(s)
- Deborah A Salzer
- Neurovascular Research Laboratory, School of Kinesiology, Rm. 3110 Thames Hall, The Univ. of Western Ontario, London, ON, Canada N6A 3K7
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90
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Pyke KE, Poitras V, Tschakovsky ME. Brachial artery flow-mediated dilation during handgrip exercise: evidence for endothelial transduction of the mean shear stimulus. Am J Physiol Heart Circ Physiol 2008; 294:H2669-79. [DOI: 10.1152/ajpheart.01372.2007] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exercise elevates shear stress in the supplying conduit artery. Although this is the most relevant physiological stimulus for flow-mediated dilation (FMD), the fluctuating pattern of shear that occurs may influence the shear stress-FMD stimulus response relationship. This study tested the hypothesis that the brachial artery FMD response to a step increase in shear is influenced by the fluctuating characteristics of the stimulus, as evoked by forearm exercise. In 16 healthy subjects, we examined FMD responses to step increases in shear rate in three conditions: stable shear upstream of heat-induced forearm vasodilation (FHStable); fluctuating shear upstream of heat-induced forearm vasodilation and rhythmic forearm cuff inflation/deflation (FHFluctuating); and fluctuating shear upstream of exercise-induced forearm vasodilation (FEStep Increase). The mean increase in shear rate (±SD) was the same in all trials (FHFluctuating: 51.69 ± 15.70 s−1; FHStable: 52.16 ± 14.10 s−1; FEStep Increase: 50.14 ± 13.03 s−1 P = 0.131). However, the FHFluctuating and FEStep Increase trials resulted in a fluctuating shear stress stimulus with rhythmic high and low shear periods that were 96.18 ± 24.54 and 11.80 ± 7.30 s−1, respectively. The initial phase of FMD (phase I) was followed by a second, delayed-onset FMD and was not different between conditions (phase I: FHFluctuating: 5.63 ± 2.15%; FHStable: 5.33 ± 1.85%; FEStep Increase: 5.30 ± 2.03%; end-trial: FHFluctuating: 7.76 ± 3.40%; FHStable: 7.00 ± 3.03%; FEStep Increase: 6.68 ± 3.04%; P = 0.196). Phase I speed also did not differ ( P = 0.685). In conclusion, the endothelium transduced the mean shear when exposed to shear fluctuations created by a typical handgrip protocol. Muscle activation did not alter the FMD response. Forearm exercise may provide a viable technique to investigate brachial artery FMD in humans.
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91
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Pyke KE, Hartnett JA, Tschakovsky ME. Are the dynamic response characteristics of brachial artery flow-mediated dilation sensitive to the magnitude of increase in shear stimulus? J Appl Physiol (1985) 2008; 105:282-92. [PMID: 18467554 DOI: 10.1152/japplphysiol.01190.2007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine the dynamic characteristics of brachial artery dilation in response to step increases in shear stress [flow-mediated dilation (FMD)]. Brachial artery diameter (BAD) and mean blood velocity (MBV) (Doppler ultrasound) were obtained in 15 healthy subjects. Step increases in MBV at two shear stimulus magnitudes were investigated: large (L; maximal MBV attainable), and small (S; MBV at 50% of the large step). Increase in shear rate (estimate of shear stress: MBV/BAD) was 76.8 +/- 15.6 s(-1) for L and 41.4 +/- 8.7 s(-1) for S. The peak %FMD was 14.5 +/- 3.8% for L and 5.7 +/- 2.1% for S (P < 0.001). Both the L (all subjects) and the S step trials (12 of 15 subjects) elicited a biphasic diameter response with a fast initial phase (phase I) followed by a slower final phase. Relative contribution of phase I to total FMD when two phases occurred was not sensitive to shear rate magnitude (r(2) = 0.003, slope P = 0.775). Parameters quantifying the dynamics of the FMD response [time delay (TD), time constant (tau)] were also not sensitive to shear rate magnitude for both phases (phase I: TD r(2) = 0.03, slope P = 0.376, tau r(2) = 0.04, slope P = 0.261; final phase: TD r(2) = 0.07, slope P = 0.169, tau r(2) = 0.07, slope P = 0.996). These data support the existence of two distinct mechanisms, or sets of mechanisms, in the human conduit artery FMD response that are proportionally sensitive to shear stimulus magnitude and whose dynamic response is not sensitive to shear stimulus magnitude.
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Affiliation(s)
- K E Pyke
- Queen's University, Kingston, Ontario, Canada
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92
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Padilla J, Harris RA, Wallace JP. Can the measurement of brachial artery flow-mediated dilation be applied to the acute exercise model? Cardiovasc Ultrasound 2007; 5:45. [PMID: 18039389 PMCID: PMC2211283 DOI: 10.1186/1476-7120-5-45] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 11/26/2007] [Indexed: 01/22/2023] Open
Abstract
The measurement of flow-mediated dilation using high-resolution ultrasound has been utilized extensively in interventional trials evaluating the salutary effect of drugs and lifestyle modifications (i.e. diet or exercise training) on endothelial function; however, until recently researchers have not used flow-mediated dilation to examine the role of a single bout of exercise on vascular function. Utilizing the acute exercise model can be advantageous as it allows for an efficient manipulation of exercise variables (i.e. mode, intensity, duration, etc.) and permits greater experimental control of confounding variables. Given that the application of flow-mediated dilation in the acute exercise paradigm is expanding, the purpose of this review is to discuss methodological and physiological factors pertinent to flow-mediated dilation in the context of acute exercise. Although the scientific rationale for evaluating endothelial function in response to acute exercise is sound, few concerns warrant attention when interpreting flow-mediated dilation data following acute exercise. The following questions will be addressed in the present review: Does the measurement of flow-mediated dilation influence subsequent serial measures of flow-mediated dilation? Do we need to account for diurnal variation? Is there an optimal time to measure post-exercise flow-mediated dilation? Is the post-exercise flow-mediated dilation reproducible? How is flow-mediated dilation interpreted considering the hemodynamic and sympathetic changes associated with acute exercise? Can the measurement of endothelial-independent dilation affect the exercise? Evidence exists to support the methodological appropriateness for employing flow-mediated dilation in the acute exercise model; however, further research is warranted to clarify its interpretation following acute exercise.
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Affiliation(s)
- Jaume Padilla
- Clinical Exercise Physiology Laboratory, Department of Kinesiology, Indiana University, Bloomington, IN, USA
| | - Ryan A Harris
- Clinical Exercise Physiology Laboratory, Department of Kinesiology, Indiana University, Bloomington, IN, USA
- Physiology Division, Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Janet P Wallace
- Clinical Exercise Physiology Laboratory, Department of Kinesiology, Indiana University, Bloomington, IN, USA
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93
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Barr RG, Mesia-Vela S, Austin JHM, Basner RC, Keller BM, Reeves AP, Shimbo D, Stevenson L. Impaired flow-mediated dilation is associated with low pulmonary function and emphysema in ex-smokers: the Emphysema and Cancer Action Project (EMCAP) Study. Am J Respir Crit Care Med 2007; 176:1200-7. [PMID: 17761614 PMCID: PMC2176103 DOI: 10.1164/rccm.200707-980oc] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
RATIONALE Basic science research suggests a causal role for endothelial dysfunction in chronic obstructive pulmonary disease (COPD). Clinical studies examining endothelial function are lacking, particularly early in the disease. Flow-mediated dilation (FMD) is a physiologic measure of endothelial reactivity to endogenous nitric oxide. OBJECTIVES We hypothesized that lower FMD among former smokers would be associated with lower post-bronchodilator FEV(1), higher percentage of emphysema using computed tomography (CT) and lower diffusing capacity. METHODS We measured FMD, pulmonary function, and CT percentage of emphysema in a random sample of 107 cotinine-confirmed former smokers in the ongoing EMCAP study. FMD was defined as percentage change in the brachial artery diameter with reactive hyperemia. Generalized additive models were used to adjust for potential confounders and assess linearity. MEASUREMENTS AND MAIN RESULTS Mean age of participants was 71 +/- 5 years, 46% were female, and pack-years averaged 48 +/- 26. Mean FMD was 3.8 +/- 3.1%; mean post-bronchodilator FEV(1), 2.3 +/- 0.8 L; and mean CT percentage of emphysema, 26 +/- 10%. A 1 SD decrease in FMD was associated with a 132-ml (95% confidence interval, 16-248 ml; P = 0.03) decrement in post-bronchodilator FEV(1) and a 2.6% (95% confidence interval, 0.5-4.7%; P = 0.02) increase in CT percentage of emphysema in fully adjusted models. These associations were linear across the spectrum from normality to disease, independent of smoking history, and also significant among participants without COPD. Associations with diffusing capacity were consistent but nonsignificant (P = 0.09). The FMD-FEV(1) association was entirely attributable to percentage of emphysema. CONCLUSIONS Impaired endothelial function, as measured by FMD, was associated with lower FEV(1) and higher CT percentage of emphysema in former smokers early in COPD.
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Affiliation(s)
- R Graham Barr
- Dr.P.H., Presbyterian Hospital 9 East, Room 105, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA.
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94
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Pyke KE, Tschakovsky ME. Peak vs. total reactive hyperemia: which determines the magnitude of flow-mediated dilation? J Appl Physiol (1985) 2007; 102:1510-9. [PMID: 17170205 DOI: 10.1152/japplphysiol.01024.2006] [Citation(s) in RCA: 230] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the independent contributions of the peak and continued reactive hyperemia on flow-mediated dilation (FMD). 1) For the duration manipulation experiment (DME), 10 healthy males experienced reactive hyperemia durations of 10 s, 20 s, 30 s, 40 s, 50 s, or full reactive hyperemia (RH). 2) For the peak manipulation experiment (PME), eight healthy males experienced reactive hyperemia trials with three peak shear rate magnitudes (large, medium, and small). Data are means ± SD. For the DME, peak shear rate was not different between trials ( P = 0.326). Shear rate area under the curve (AUC) was P < 0.001. Peak %FMD was dependent on shear rate AUC: 10 s, 2.7 ± 1.3; 20 s, 6.2 ± 1.9; 30 s, 7.9 ± 2.9; 40 s, 8.3 ± 3.2; 50 s, 7.9 ± 3.2; full RH, 9.3 ± 4.1, with 10 and 20 s less than full RH ( P < 0.001). For the PME, peak shear rate was different between trials (large, 1,049.1 ± 285.8; medium, 726.4 ± 228.8; small, 512.8 ± 161.8; P < 0.001). AUC of the continued shear rate was not ( P = 0.412). Peak %FMD was unaffected by peak shear rate (large, 7.0 ± 2.7%; medium, 7.4 ± 2.6%; small, 6.6 ± 1.8%; P = 0.542). Peak and AUC shear stimulus were not significantly related in full RH ( r2 = 0.35, P = 0.07). We conclude that the shear stimulus AUC, not the peak itself, is the critical determinant of the peak FMD response. This indicates AUC as the best method of quantifying reactive hyperemia shear stimulus for %FMD normalization.
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Affiliation(s)
- Kyra E Pyke
- Human Vascular Control Laboratory, School of Kinesiology and Health Studies and Department of Physiology, Queen's University, Kingston, Ontario, Canada
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95
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Kaufman CL, Kaiser DR, Steinberger J, Dengel DR. Relationships between heart rate variability, vascular function, and adiposity in children. Clin Auton Res 2007; 17:165-71. [PMID: 17390101 DOI: 10.1007/s10286-007-0411-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2006] [Accepted: 02/14/2007] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To examine the relationships and interactions between cardiovascular autonomic nervous system (cANS) function, adiposity, and vascular function in children of varying levels of adiposity. METHODS Participants were children (19 M, 17 F, age = 11.5 +/- 0.1 years) who had cANS function assessed via heart rate variability (HRV) methods during resting conditions. Vascular function was assessed with brachial artery flow-mediated dilation (FMD) and nitroglycerin-induced dilation. Spectral power of HRV was calculated for high frequency normalized units (HFnu; measure of PSNS activity) and low frequency:high frequency ratio (LF:HF; overall sympathovagal balance). A blood sample was drawn for measurement of fasting insulin, glucose, lipids, and C-reactive protein (CRP). Results were reported as mean +/- SEM. RESULTS FMD peak dilation was positively related to HFnu (r = 0.48, P = 0.01) and negatively related to LF:HF (r = -0.51, P = 0.01) indicating that reduced parasympathetic activity and states of dysfunctional sympathovagal balance were associated with decreased vascular function. After adjustment for confounding factors (insulin, CRP, age) and fat mass, the relationships between these measures of cANS and vascular function remained moderately strong and significant. DISCUSSION These data indicate a relationship between cANS and vascular function that is independent of fat mass, inflammation (CRP), and fasting insulin in children of varying levels of adiposity. These relationships and the mechanisms by which they exist require further study to allow for the identification of appropriate therapies for children with high levels of adiposity given the likelihood of them having concomitant cANS and vascular dysfunction.
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96
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Parker BA, Smithmyer SL, Jarvis SS, Ridout SJ, Pawelczyk JA, Proctor DN. Evidence for reduced sympatholysis in leg resistance vasculature of healthy older women. Am J Physiol Heart Circ Physiol 2006; 292:H1148-56. [PMID: 17071730 DOI: 10.1152/ajpheart.00729.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Inhibition of a sympathetic stimulus (i.e., sympatholysis) during forearm exercise is reduced with age in women. This age-related alteration has not been characterized in the lower extremity vasculature of women, and the potential for blunting of the conduit artery dilatory response to a sudden increase in shear stress [flow-mediated dilation (FMD)] has not been examined in older adults of either sex. In the present study, we assessed popliteal artery diameter and velocity (Doppler ultrasound) in 16 young (23 +/- 1 yr) and 14 older (69 +/- 1 yr) women after 5 min of distal calf occlusion (FMD), 3 min of hand immersion in ice water [cold pressor test (CPT)], and 5 min of distal calf occlusion combined with hand immersion in ice water (FMD+CPT). Peak popliteal conductance after 5-min ischemia was not significantly different in young vs. older women. During the combined stimulus (FMD+CPT), the magnitude of vasoconstriction in the calf (reduction in peak popliteal artery conductance) was similar (5-8%), despite reduced resting adrenergic sensitivity to CPT [young (Y): -27.3 +/- 3.8%; older (O): -15.8 +/- 2.2%; P < 0.05] and blunted muscle sympathetic nerve activity responses to CPT (Y: 12.7 +/- 3.6 bursts/min; O: 7.8 +/- 2.5 bursts/min; P < 0.05) in older women. Popliteal FMD, normalized to the shear stimulus, was attenuated by 60-70% in older women. Peak popliteal diameter, measured during the combined stimulus (FMD+CPT), was blunted in young but not in older women (Y FMD: 5.5 +/- 0.1 mm; Y FMD+CPT: 5.4 +/- 0.1 mm; P = 0.03; O FMD: 5.8 +/- 0.2 mm; O FMD+CPT: 5.8 +/- 0.2 mm). These results confirm previous findings of diminished reactivity in the conduit arteries of older humans and provide the first evidence of reduced sympatholysis in the leg resistance vasculature of older women.
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Affiliation(s)
- Beth A Parker
- Department of Kinesiology, Pennsylvania State University, 105 Noll Laboratory, University Park, PA 16802-6900, USA
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97
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Parker BA, Ridout SJ, Proctor DN. Age and flow-mediated dilation: a comparison of dilatory responsiveness in the brachial and popliteal arteries. Am J Physiol Heart Circ Physiol 2006; 291:H3043-9. [PMID: 16861699 DOI: 10.1152/ajpheart.00190.2006] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous investigations of age-associated changes in flow-mediated vasodilation (FMD) in women have been limited to the upper extremity and have not accounted for possible age differences in the stimulus for dilation. The purpose of the present study was to compare age differences in brachial and popliteal FMD and its stimulus (changes in shear rate following occlusion). Ultrasound-derived diameters and Doppler flow velocities of the brachial and popliteal arteries were measured in 14 young (20- to 30-yr-old) and 14 older (60- to 79-yr-old) healthy women at rest and during and after 5 min of distal cuff occlusion. Resting diameters were similar (both P > 0.39) in both age groups. Peak shear rate did not differ with age in either artery: approximately 1,300-1,400 and approximately 400-500 s(-1) in brachial and popliteal arteries, respectively. FMD (percent change above diameter measured during occlusion) was approximately 50-60% lower (P < 0.05) in the brachial (15.8 + 0.8% vs. 8.1 + 1.5%) and popliteal (4.6 +/- 0.7% vs. 1.8 +/- 0.4%) arteries of the older women. The normalized response of the brachial and popliteal arteries (%FMD per unit change in shear rate) was also reduced with age (55% and 53%, respectively) but did not exhibit limb specificity. Additionally, endothelium-independent dilation, as assessed by administration of nitroglycerin, was similarly blunted (by 45-65%) in brachial and popliteal arteries of older women. These results suggest that 1) brachial and popliteal artery FMD (after 5 min of distal occlusion) are similarly reduced with age, 2) when normalized to the change in shear stimulus, both arteries are equally responsive to 5 min of distal cuff occlusion in women, and 3) the age-associated decline in FMD may be attributable in part to diminished smooth muscle responsiveness.
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Affiliation(s)
- Beth A Parker
- Dept. of Kinesiology, The Pennsylvania State University, University Park, PA 16802-6900, USA
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98
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Thijssen DHJ, de Groot P, Kooijman M, Smits P, Hopman MTE. Sympathetic nervous system contributes to the age-related impairment of flow-mediated dilation of the superficial femoral artery. Am J Physiol Heart Circ Physiol 2006; 291:H3122-9. [PMID: 16844924 DOI: 10.1152/ajpheart.00240.2006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The physiological aging process is associated with endothelial dysfunction, as assessed by flow-mediated dilation (FMD). Aging is also characterized by increased sympathetic tone. Therefore, the aim of the present study is to assess whether acute changes in sympathetic activity alter FMD in the leg. For this purpose, the FMD of the superficial femoral artery was determined in 10 healthy young (22 +/- 1 yr) and 8 healthy older (69 +/- 1 yr) men in three different conditions: 1) at baseline, 2) during reduction of sympathetic activity, and 3) during sympathetic stimulation. Reduction of sympathetic activity was achieved by performing a maximal cycling exercise, leading to postexercise attenuation of the sympathetic responsiveness in the exercised limb. A cold pressor test was used to increase sympathetic activity. Nitroglycerin (NTG) was used to assess endothelium-independent vasodilation in all three conditions. Our results showed that, in older men, the FMD and NTG responses were significantly lower compared with young men (P = 0.001 and P = 0.02, respectively). In older men, sympathetic activity significantly affected the FMD response [repeated-measures (RM) ANOVA: P = 0.01], with a negative correlation between the level of sympathetic activity and FMD (R = -0.41, P = 0.049). This was not the case for NTG responses (ANOVA; P = 0.48). FMD and NTG responses in young men did not differ among the three conditions (RM-ANOVA: P = 0.32 and P = 0.31, respectively). In conclusion, in older men, FMD of the femoral artery is impaired. Local attenuation of the sympathetic responsiveness partly restores the FMD in these subjects. In contrast, in young subjects, acute modulation of the sympathetic nervous system activity does not alter flow-mediated vasodilation in the leg.
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Affiliation(s)
- Dick H J Thijssen
- Dept. of Physiology, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
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