An independent relationship between muscle sympathetic nerve activity and pulse wave velocity in normal humans

Hemodynamic phenotypes in chronic kidney disease patients based on linear regression of blood pressure parameters

Classic and non-classic cardiovascular (CV) risk factors accumulate in chronic kidney disease (CKD), contributing to vascular remodeling and hemodynamic abnormalities. This study aimed to determine hemodynamic phenotypes based on linear regression of blood pressure (BP) parameters in stage G3-G4 CKD patients at very high CV risk. 24-h ambulatory BP monitoring (ABPM), carotid-femoral pulse wave velocity (PWV) and central BP were obtained from 52 patients (aged 60 ± 11 years, BMI 30 ± 6 kg/m2) with stage G3-G4 CKD (eGFR 44 ± 12 mL/min./1.73 m2). Linear BP regression coefficients were generated to determine hemodynamic phenotypes using ABPM data. Coexisting hypertension was present in 45 (86%) patients, out of whom 33 (73%) had BP controlled. 24-h mean systolic/diastolic BP was 128 ± 18/75 ± 12 mm Hg. Twenty-six patients demonstrated the harmonious (H) and 26 patients diastolic dysfunctional (D) hemodynamic phenotypes. eGFR was not significantly different between both phenotypes. Compared to phenotype H, patients with phenotype D were older (57 ± 11 vs. 63 ± 10 years, p = .04), had higher PWV (8.2 [7.3-10.3] vs. 9.7 [8.3-10.9] m/s, p = .02), ambulatory arterial stiffness index (AASI) (0.31 ± 0.1 vs. 0.40 ± 0.1, p = .02), systolic BP (128 [122-130] vs. 137 [130-150] mm Hg, p = .001) and systolic BP variability (BPV) (11.7 ± 2.3 vs. 15.7 ± 3.4 mm Hg, p < .0001). Our findings suggest that one in two patients with stage G3-G4 CKD demonstrates an unfavorable D hemodynamic phenotype based on a linear regression model, associated with higher PWV, AASI, systolic BP, and systolic BPV. Further studies are required to assess the clinical utility of hemodynamic phenotypes and whether the D phenotype may predict latent circulatory disorders and outcomes.

Perfusion and pulsatile pressure: their relationship with target organ damage in the African-PREDICT study

BACKGROUND

Hypertension is the leading risk factor for subclinical target-organ damage (TOD) and cardiovascular disease (CVD). Little is known about the relationship between different pressure measures and subclinical TOD, especially in young populations. We compared the strength of associations of subclinical TOD markers with perfusion and pulsatile pressure in young adults.

METHODS

A total of 1 187 young adults from the African-PREDICT study were included. Ambulatory mean arterial pressure (MAP) and pulse pressure (PP) was obtained. Markers of subclinical TOD were measured and included left ventricular mass index (LVMi), carotid intimamedia thickness (cIMT), carotidfemoral pulse wave velocity (cfPWV), central retinal arteriolar equivalent (CRAE) and albumin to creatinine ratio (ACR).

RESULTS

Measures of sub-clinical TOD (cIMT, cfPWV and CRAE), associated stronger with perfusion pressure (all p < 0.001) than pulsatile pressure in unadjusted models. Stronger associations were found between cfPWV (adjusted R2 = 0.26), CRAE (adjusted R2 = 0.12) and perfusion pressure (all p ≤ 0.001) than pulsatile pressure independent of several non-modifiable and modifiable risk factors.

CONCLUSIONS

In young, healthy adults, perfusion pressure is more strongly associated with subclinical TOD markers than pulsatile pressure. These findings contribute to the understanding of the development of early cardiovascular changes and may guide future intervention strategies.

Seated Elliptical Exercise, But Not Periodic Standing, Alleviates Sitting-Induced Changes to Arterial Wave Reflections

PURPOSE

Sedentary behavior may contribute to increased central wave reflection due to associated peripheral vasoconstriction, yet its impact on central hemodynamics and the mitigating effects of interventional strategies have not been thoroughly investigated. We tested whether standing or seated elliptical breaks alleviate the deleterious effects of prolonged sitting on central wave reflections.

METHODS

Eighteen healthy adults (9 9 females, 25 ± 3 yr) completed three 3-h protocols on separate days: uninterrupted sitting, sitting with periodic standing, and sitting with periodic seated elliptical activity. Central wave reflection, central pulse wave velocity, and lower-limb pulse wave velocity were measured before and after each intervention.

RESULTS

Central relative wave reflection magnitude (RM) increased during sitting (0.31 ± 0.05 to 0.35 ± 0.05; P < 0.01) but did not change after standing (0.30 ± 0.05 to 0.32 ± 0.04; P = 0.19) or elliptical protocols (0.30 ± 0.05 to 0.30 ± 0.04; P > 0.99). The change in RM during prolonged sitting (ΔRM) was attenuated with elliptical activity (0.04 ± 0.05 vs 0.00 ± 0.03; P = 0.02) but not with periodic standing (0.04 ± 0.04 vs 0.02 ± 0.05; P = 0.54). In addition, augmentation index and central pulse wave velocity increased after sitting (both P < 0.01) and periodic standing (both P < 0.01) but were unchanged after elliptical activity. Lower limb pulse wave velocity did not change after sitting ( P = 0.73) or standing ( P = 0.21) but did decrease after elliptical activity ( P = 0.03).

CONCLUSIONS

Prolonged sitting without interruptions increased central wave reflection, whereas elliptical but not standing interruptions were able to ameliorate multiple sitting-induced vascular consequences. More work is required to examine the long-term effectiveness of interruption strategies, as well as the optimal type, frequency, and duration for reducing vascular risk associated with sedentary behaviors.

Sex differences in sympathetic activity and pulse wave velocity in adults with chronic kidney disease

Chronic kidney disease (CKD) is characterized by sympathetic nervous system (SNS) overactivity that contributes to increased vascular stiffness and cardiovascular risk. Although it is well established that SNS activity and vascular stiffness are substantially elevated in CKD, whether sex differences in autonomic and vascular function exist in CKD remains unknown. We tested the hypothesis that compared with females, males with CKD have higher baseline sympathetic activity that is related to increased arterial stiffness. One hundred twenty-nine participants (96 males and 33 females) with CKD stages III and IV were recruited and enrolled. During two separate study visits, vascular stiffness was assessed by measuring carotid-to-femoral pulse wave velocity (cfPWV), and resting muscle sympathetic nerve activity (MSNA) was measured by microneurography. Males with CKD had higher resting MSNA compared with females with CKD (68 ± 16 vs. 55 ± 14 bursts/100 heart beats, P = 0.005), whereas there was no difference in cfPWV between the groups (P = 0.248). Resting MSNA was not associated with cfPWV in both males and females. In conclusion, males with CKD have higher resting sympathetic activity compared with females with CKD. However, there was no difference in vascular stiffness between the sexes. There was no correlation between resting MSNA and cfPWV, suggesting that non-neural mechanisms may play a greater role in the progression of vascular stiffness in CKD, particularly in females.NEW & NOTEWORTHY Males with chronic kidney disease (CKD) have higher resting muscle sympathetic nerve activity (MSNA) compared with females. There was no correlation between MSNA and carotid-to-femoral pulse wave velocity (cfPWV), suggesting that non-neural mechanisms may play a greater role in the progression of vascular stiffness in CKD. Sex differences in SNS activity may play a mechanistic role in observations from epidemiological studies suggesting greater cardiovascular risk in males compared with females with CKD.

Association of blood pressure and heart rate with carotid markers of vascular remodeling in the young: a case for early prevention

OBJECTIVE

The association of childhood blood pressure (BP) and heart rate (HR) with intermediate markers of cardiovascular disease several decades later has been shown, but studies on more short-term outcomes are scarce. Using population-based data, this study investigates the association of four BP parameters and HR in childhood with three carotid markers for vascular remodeling one decade later.

METHODS

At the 11-year follow-up, 4607 participants of the nationwide KiGGS cohort aged 14 to 28 years had semi-automated sonographic carotid intima media thickness (CIMT) measurements. We investigated associations of baseline (age 3-17 years) and follow-up SBP, DBP, mean arterial pressure (MAP), pulse pressure (PP) and resting heart rate (RHR), with CIMT and lumen diameter at or above the 90th percentile and distensibility coefficient at or below the tenth percentile in logistic regressions. Analyses were further adjusted using a composite cardiovascular risk (CVR) score of BMI, triglycerides, total/HDL-cholesterol-ratio and HbA1c.

RESULTS

SBP, DBP, MAP and RHR were significantly and similarly associated with all carotid measures 11 years later, for example an odds ratio (OR) of 1.17 [confidence interval (CI) 1.06-1.29] for one standard deviation SBP increase with elevated CIMT when adjusting for sex, age and CVR score. Cross-sectionally, the strongest association was found for MAP with reduced distensibility coefficient (OR 1.76; CI 1.59-1.94).

CONCLUSION

This population-based cohort study shows robust and consistent associations between childhood BP and RHR and three carotid measures of vascular remodeling only one decade later, clearly underscoring the potential importance of preventing high BP already early in the life course.

Fructose-induced salt-sensitive blood pressure differentially affects sympathetically mediated aortic stiffness in male and female Sprague-Dawley rats

Hypertension is the leading risk factor for major adverse cardiovascular events (MACE). Aortic stiffness and sympathoexcitation are robust predictors of MACE. Combined high fructose and sodium intake increases arterial pressure, aortic stiffness, renin, and sympathetic nerve activity in male rats. We hypothesized that activation of the renin angiotensin system (RAS) and/or the sympathetic system mediates aortic stiffness in rats with fructose-induced salt-sensitive blood pressure. Male and female Sprague-Dawley rats ingested 20% fructose or 20% glucose in drinking water with 0.4% NaCl chow for 1 week. Then, fructose-fed rats were switched to 4% NaCl chow (Fru + HS); glucose-fed rats remained on 0.4% NaCl chow (Glu + NS, controls for caloric intake). After 2 weeks, mean arterial pressure (MAP) and aortic pulsed wave velocity (PWV) were evaluated at baseline or after acute intravenous vehicle, clonidine, enalapril, losartan, or hydrochlorothiazide. Baseline global longitudinal strain (GLS) was also assessed. MAP and PWV were greater in male Fru + HS versus Glu + NS male rats (p < 0.05 and p < 0.001, respectively). PWV was similar between the female groups. Despite similarly reduced MAP after clonidine, PWV decreased in Fru + HS versus Glu + NS male rats (p < 0.01). Clonidine induced similar decreases in MAP and PWV in females on either diet. GLS was lower in Fru + HS versus Glu + NS male rats and either of the female groups. Thus, acute sympathoinhibition improved aortic compliance in male rats with fructose salt-sensitive blood pressure. Female rats retained aortic compliance regardless of diet. Acute RAS inhibition exerted no significant effects. Male rats on fructose high salt diet displayed an early deficit in myocardial function. Taken together, these findings suggest that adult female rats are protected from the impact of fructose and high salt diet on blood pressure, aortic stiffness, and early left ventricular dysfunction compared with male rats.

Effects of Acute and Chronic Exercise in Hypoxia on Cardiovascular and Glycemic Parameters in Patients with Type 2 Diabetes: A Systematic Review

Kindlovits, Raquel, Alberto Mello da Silva Pereira, Ana Catarina Sousa, João Luís Viana,and Vitor Hugo Teixeira. Effects of acute and chronic exercise in hypoxia on cardiovascular and glycemic parameters in patients with type 2 diabetes: a systematic review. High Alt Med Biol. 23:301-312, 2022. Background: Exercise in hypoxia (EH, decreased oxygen availability) has been proposed as a potential therapeutic intervention to promote angiogenesis and improve glucose metabolism to a greater extent than exercise under normoxia (normal ambient air) in patients with type 2 diabetes (T2D). Currently, there are no studies that systematize the existent evidence. This study aims to systematically review the literature and qualitatively evaluate the effects of acute and chronic EH on cardiovascular and glycemic parameters in T2D patients. Methods: A structured search was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines until March 2021, in the MEDLINE/PubMed, Scopus, and Web of Science databases. The inclusion criteria were as follows: (1) randomized and nonrandomized trials, (2) in complication-free patients with T2D, (3) in which EH was compared with exercise in normoxia or with baseline data, and (4) published in English. Results: Six articles (64 subjects) met the inclusion criteria and were reviewed to data extraction. Four articles investigated the acute effect of EH (33 subjects), and two articles investigated the chronic effect of EH (31 subjects), ranging from 6 to 8 weeks. All studies used a cycle ergometer as exercise. Acute EH benefits insulin sensitivity, blood glucose, vascular endothelial growth factor, and metalloproteinase-9, while chronic EH benefits nitric oxide synthase in erythrocytes, but not brachial artery flow-mediated dilation. Conclusion: Acute EH improves glucose homeostasis in T2D patients, which was not seen with chronic EH. Both acute EH and chronic EH improve angiogenesis regulators, but not vascular function. Despite the putative benefits of EH in patients with T2D, the evidence is still scarce and further research is needed before recommendations can be provided.

Autonomic and circulatory alterations persist despite adequate resuscitation in a 5-day sepsis swine experiment

Autonomic and vascular failures are common phenotypes of sepsis, typically characterized by tachycardia despite corrected hypotension/hypovolemia, vasopressor resistance, increased arterial stiffness and decreased peripheral vascular resistance. In a 5-day swine experiment of polymicrobial sepsis we aimed at characterizing arterial properties and autonomic mechanisms responsible for cardiovascular homeostasis regulation, with the final goal to verify whether the resuscitation therapy in agreement with standard guidelines was successful in restoring a physiological condition of hemodynamic profile, cardiovascular interactions and autonomic control. Twenty pigs were randomized to polymicrobial sepsis and protocol-based resuscitation or to prolonged mechanical ventilation and sedation without sepsis. The animals were studied at baseline, after sepsis development, and every 24 h during the 3-days resuscitation period. Beat-to-beat carotid blood pressure (BP), carotid blood flow, and central venous pressure were continuously recorded. The two-element Windkessel model was adopted to study carotid arterial compliance, systemic vascular resistance and characteristic time constant τ. Effective arterial elastance was calculated as a simple estimate of total arterial load. Cardiac baroreflex sensitivity (BRS) and low frequency (LF) spectral power of diastolic BP were computed to assess autonomic activity. Sepsis induced significant vascular and autonomic alterations, manifested as increased arterial stiffness, decreased vascular resistance and τ constant, reduced BRS and LF power, higher arterial afterload and elevated heart rate in septic pigs compared to sham animals. This compromised condition was persistent until the end of the experiment, despite achievement of recommended resuscitation goals by administered vasopressors and fluids. Vascular and autonomic alterations persist 3 days after goal-directed resuscitation in a clinically relevant sepsis model. We hypothesize that the addition of these variables to standard clinical markers may better profile patients' response to treatment and this could drive a more tailored therapy which could have a potential impact on long-term outcomes.

Dietary Inorganic Nitrate/Nitrite Supplementation Reduces Central and Peripheral Blood Pressure in Patients With Type 2 Diabetes Mellitus

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) have increased cardiovascular risk due to elevated blood pressure (BP). As low levels of nitric oxide (NO) may contribute to increased BP, we determined if increasing NO bioavailability via eight weeks of supplementation with beetroot juice containing inorganic nitrate/nitrite (4.03 mmol nitrate, 0.29 mmol nitrite) improves peripheral and central BP relative to nitrate/nitrite-depleted beetroot juice.

METHODS

Peripheral and central BP were assessed at heart-level in supine subjects using a brachial artery catheter and applanation tonometry, respectively.

RESULTS

Nitrate/nitrite supplementation reduced peripheral systolic BP (148 ± 16 to 142 ± 18 mm Hg, P < 0.05) but not placebo (150 ± 19 to 149 ± 17 mm Hg, P = 0.93); however, diastolic BP was unaffected (supplement-by-time P = 0.08). Central systolic BP (131 ± 16 to 127 ± 17 mm Hg) and augmented pressure (13.3 ± 6.6 to 11.6 ± 6.9 mm Hg, both P < 0.05) were reduced after nitrate/nitrite, but not placebo (134 ± 17 to 135 ± 16 mm Hg, P = 0.62; 14.1 ± 6.6 to 15.2 ± 7.4 mm Hg, P = 0.20); central diastolic BP was unchanged by the interventions (supplement-by-time P = 0.16). Inorganic nitrate/nitrite also reduced AIx (24.3 ± 9.9% to 21.0 ± 9.6%) whereas no changes were observed following placebo (24.6 ± 9.3% to 25.6 ± 9.9%, P = 0.46).

CONCLUSIONS

Inorganic nitrate/nitrite supplementation improves peripheral and central BP as well as AIx in T2DM.

CLINICAL TRIALS REGISTRATION

Trial Number NCT02804932.

Relationships between muscle sympathetic nerve activity and novel indices of arterial stiffness using single oscillometric cuff in patients with hypertension

The arterial velocity pulse index (AVI) and arterial pressure-volume index (API) have been proposed as new arterial stiffness indices that can be measured using an oscillometric cuff. Sympathetic nerve activity (SNA) contributes to arterial stiffness via increasing vascular smooth muscle tone. However, the associations between SNA and the AVI or API are not understood. The purpose of this study was to evaluate the relationships between muscle sympathetic nerve activity (MSNA) and the AVI or API in healthy individuals and patients with hypertension (HT). Forty healthy individuals (40.1 ± 15.2 years, 8 females) (healthy group) and 40 patients with HT (60.2 ± 13.6, 18 females) (HT group) were included in this study. The AVI, API, MSNA, beat-by-beat blood pressure, and heart rate were recorded simultaneously. The AVI and API were higher in the HT group than in the healthy group (AVI, 26.1 ± 7.6 vs. 16.5 ± 4.0, p < 0.001; API, 31.2 ± 8.6 vs. 25.5 ± 7.2, p = 0.002). MSNA in the HT group was also higher than in the healthy group (p < 0.001). MSNA was correlated with the AVI, but not with the API, in both the healthy group (R = 0.52, p = 0.001) and HT group (R = 0.57, p < 0.001). MSNA was independently correlated with the AVI in multivariate analysis (ß = 0.34, p = 0.001). In conclusion, AVI, obtained by a simple and less user-dependent method, was related to the MSNA in healthy individuals and patients with HT.

Six-month longitudinal tracking of arterial stiffness and blood pressure in young adults following SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can increase arterial stiffness 3–4 wk following infection, even among young, healthy adults. However, the long-term impacts of SARS-CoV-2 infection on cardiovascular health and the duration of recovery remain unknown. The purpose of this study was to elucidate potential long-lasting effects of SARS-CoV-2 infection on markers of arterial stiffness among young adults during the 6 mo following infection. Assessments were performed at months 1, 2, 3, 4, and ∼6 following SARS-CoV-2 infection. Doppler ultrasound was used to measure carotid-femoral pulse wave velocity (cfPWV) and carotid stiffness, and arterial tonometry was used to measure central blood pressures and aortic augmentation index at a heart rate of 75 beats·min⁻¹ (AIx@HR75). Vascular (VCAM-1) and intracellular (ICAM-1) adhesion molecules were analyzed as circulating markers of arterial stiffness. From months 1–6, a significant reduction in cfPWV was observed (month 1: 5.70 ± 0.73 m·s⁻¹; month 6: 4.88 ± 0.65 m·s⁻¹; P < 0.05) without any change in carotid stiffness measures. Reductions in systolic blood pressure (month 1: 123 ± 8 mmHg; month 6: 112 ± 11 mmHg) and mean arterial pressure (MAP; month 1: 97 ± 6 mmHg; month 6: 86 ± 7 mmHg) were observed (P < 0.05), although AIx@HR75 did not change over time. The month 1–6 change in cfPWV and MAP were correlated (r = 0.894; P < 0.001). A reduction in VCAM-1 was observed at month 3 compared with month 1 (month 1: 5,575 ± 2,242 pg·mL⁻¹; month 3: 4,636 ± 1,621 pg·mL⁻¹; P < 0.05) without a change in ICAM-1. A reduction in cfPWV was related with MAP, and some indicators of arterial stiffness remain elevated for several months following SARS-CoV-2 infection, possibly contributing to prolonged recovery and increased cardiovascular health risks.

NEW & NOTEWORTHY We sought to investigate potential long-lasting effects of SARS-CoV-2 infection on markers of arterial stiffness among young adults for 6 mo following infection. Carotid femoral pulse wave velocity was significantly reduced while carotid stiffness measures remained unaltered over the 6-mo period. These findings suggest several months of recovery from infection may be necessary for young adults to improve various markers of arterial stiffness, possibly contributing to cardiovascular health and recovery among those infected with SARS-CoV-2.

Is It Good to Have a Stiff Aorta with Aging? Causes and Consequences

Aortic stiffness increases with advancing age, more than doubling during the human life span, and is a robust predictor of cardiovascular disease (CVD) clinical events independent of traditional risk factors. The aorta increases in diameter and length to accommodate growing body size and cardiac output in youth, but in middle and older age the aorta continues to remodel to a larger diameter, thinning the pool of permanent elastin fibers, increasing intramural wall stress and resulting in the transfer of load bearing onto stiffer collagen fibers. Whereas aortic stiffening in early middle age may be a compensatory mechanism to normalize intramural wall stress and therefore theoretically "good" early in the life span, the negative clinical consequences of accelerated aortic stiffening beyond middle age far outweigh any earlier physiological benefit. Indeed, aortic stiffness and the loss of the "windkessel effect" with advancing age result in elevated pulsatile pressure and flow in downstream microvasculature that is associated with subclinical damage to high-flow, low-resistance organs such as brain, kidney, retina, and heart. The mechanisms of aortic stiffness include alterations in extracellular matrix proteins (collagen deposition, elastin fragmentation), increased arterial tone (oxidative stress and inflammation-related reduced vasodilators and augmented vasoconstrictors; enhanced sympathetic activity), arterial calcification, vascular smooth muscle cell stiffness, and extracellular matrix glycosaminoglycans. Given the rapidly aging population of the United States, aortic stiffening will likely contribute to substantial CVD burden over the next 2-3 decades unless new therapeutic targets and interventions are identified to prevent the potential avalanche of clinical sequelae related to age-related aortic stiffness.

Aortic haemodynamics: the effects of habitual endurance exercise, age and muscle sympathetic vasomotor outflow in healthy men

PURPOSE

We determined the effect of habitual endurance exercise and age on aortic pulse wave velocity (aPWV), augmentation pressure (AP) and systolic blood pressure (aSBP), with statistical adjustments of aPWV and AP for heart rate and aortic mean arterial pressure, when appropriate. Furthermore, we assessed whether muscle sympathetic nerve activity (MSNA) correlates with AP in young and middle-aged men.

METHODS

Aortic PWV, AP, aortic blood pressure (applanation tonometry; SphygmoCor) and MSNA (peroneal microneurography) were recorded in 46 normotensive men who were either young or middle-aged and endurance-trained runners or recreationally active nonrunners (10 nonrunners and 13 runners within each age-group). Between-group differences and relationships between variables were assessed via ANOVA/ANCOVA and Pearson product-moment correlation coefficients, respectively.

RESULTS

Adjusted aPWV and adjusted AP were similar between runners and nonrunners in both age groups (all, P > 0.05), but higher with age (all, P < 0.001), with a greater effect size for the age-related difference in AP in runners (Hedges' g, 3.6 vs 2.6). aSBP was lower in young (P = 0.009; g = 2.6), but not middle-aged (P = 0.341; g = 1.1), runners compared to nonrunners. MSNA burst frequency did not correlate with AP in either age group (young: r = 0.00, P = 0.994; middle-aged: r = - 0.11, P = 0.604).

CONCLUSION

There is an age-dependent effect of habitual exercise on aortic haemodynamics, with lower aSBP in young runners compared to nonrunners only. Statistical adjustment of aPWV and AP markedly influenced the outcomes of this study, highlighting the importance of performing these analyses. Further, peripheral sympathetic vasomotor outflow and AP were not correlated in young or middle-aged normotensive men.

Effect of Nocturnal Oxygen on Blood Pressure Response to Altitude Exposure in COPD - Data from a Randomized Placebo-Controlled Cross-Over Trial

Purpose

Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to hypoxia-induced autonomic dysregulation. Hypoxemia is marked during sleep. In COPD, altitude exposure is associated with an increase in blood pressure (BP) and a decrease in baroreflex-sensitivity (BRS). Whether nocturnal oxygen therapy (NOT) may mitigate these cardiovascular autonomic changes in COPD at altitude is unknown.

Materials and Methods

In a randomized placebo-controlled cross-over trial, 32 patients with moderate-to-severe COPD living <800 m were subsequently allocated to NOT and placebo during acute exposure to altitude. Measurements were done at low altitude at 490 m and during two stays at 2048 m on NOT (3 L/min) and placebo (3 L/min, ambient air) via nasal cannula. Allocation and intervention sequences were randomized. Outcomes of interest were BP, BRS (from beat-to-beat BP measurement), BP variability (BPV), and heart rate.

Results

About 23/32 patients finished the trial per protocol (mean (SD) age 66 (5) y, FEV₁ 62 (14) % predicted) and 9/32 experienced altitude-related illnesses (8 vs 1, p < 0.05 placebo vs NOT). NOT significantly mitigated the altitude-induced increase in systolic BP compared to placebo (Δ median −5.8 [95% CI −22.2 to −1.4] mmHg, p = 0.05) but not diastolic BP (−3.5 [95% CI −12.6 to 3.0] mmHg; p = 0.21) or BPV. BRS at altitude was significantly higher in NOT than in placebo (1.7 [95% CI 0.3 to 3.4] ms/mmHg, p = 0.02).

Conclusion

NOT may protect from hypoxia-induced autonomic dysregulation upon altitude exposure in COPD and thus protect from a relevant increase in BP and decrease in BRS. NOT may provide cardiovascular benefits in COPD during conditions of increased hypoxemia and may be considered in COPD travelling to altitude.

Temporal Clustering of Skin Sympathetic Nerve Activity Bursts in Acute Myocardial Infarction Patients

Backgrounds: Acute myocardial infarction (AMI) affects the autonomic nervous system (ANS) function. The aim of our study is to detect the particular patterns of ANS regulation in AMI. We hypothesize that altered ANS regulation in AMI patients causes synchronized neural discharge (clustering phenomenon) detected by non-invasive skin sympathetic nerve activity (SKNA).

Methods: Forty subjects, including 20 AMI patients and 20 non-AMI controls, participated in the study. The wide-band bioelectrical signals (neuECG) were continuously recorded on the body surface for 5 min. SKNA was signal processed to depict the envelope of SKNA (eSKNA). By labeling the clusters, the AMI subjects were separated into non-AMI, non-cluster appearing (AMI_NCA), and cluster appearing (AMI_CA) groups.

Results: The average eSKNA was significantly correlated with HRV low-frequency (LF) power (rho = −0.336) and high-frequency power (rho = −0.372). The cross-comparison results demonstrated that eSKNA is a valid surrogate marker to assess ANS in AMI patients. The frequency of cluster occurrence was 0.01–0.03 Hz and the amplitude was about 3 μV. The LF/HF ratio of AMI_CA (median: 1.877; Q1–Q3: 1.483–2.413) revealed significantly lower than AMI_NCA (median: 3.959; Q1–Q3: 1.840–6.562). The results suggest that the SKNA clustering is a unique temporal pattern of ANS synchronized discharge, which could indicate the lower sympathetic status (by HRV) in AMI patients.

Conclusion: This is the first study to identify SKNA clustering phenomenon in AMI patients. Such a synchronized nerve discharge pattern could be detected with non-invasive SKNA signals. SKNA temporal clustering could be a novel biomarker to classify ANS regulation ability in AMI patients.

Clinical and Translational Significance: SKNA is higher in AMI patients than in control and negatively correlates with parasympathetic parameters. SKNA clustering is associated with a lower LF/HF ratio that has been shown to correlate with sudden cardiac death in AMI. The lack of SKNA temporal clustering could indicate poor ANS regulation in AMI patients.

[Renal sympathetic denervation can significantly reduce blood pressure and improve arterial stiffness in hypertensive beagles]

OBJECTIVE

To investigate the effect of renal sympathetic denervation (RDN) on blood pressure and arterial stiffness in hypertensive beagles and explore the underlying mechanism.

METHODS

Sixteen beagles were randomly divided into RDN group (n=8, fed with a high-salt high-fat diet to establish models of hypertension and treated with RDN), sham-operated group (n=4, fed with a high-salt high-fat diet to induce hypertension but only examined with renal arteriography) and control group (n=4, fed with formula dog food). The changes in blood pressure, arterial stiffness, endothelial function, and sympathetic activity were compared among the 3 groups and correlation analysis was performed.

RESULTS

All the animal models of hypertension were established successfully in the beagles. At 3 months after the RDN, the changes in systolic blood pressure (SBP) differed significantly among the 3 groups (P=0.006), and the reduction in SBP was significantly greater in RDN group than in the other two groups (P < 0.05). The variations of diastolic blood pressure (DBP) also differed significantly among the 3 groups (P=0.016), and DBP reduction was more obvious in RDN group than in the control group (P=0.007), but similar to that in the sham-operated group (P=0.052). The changes of resistance index (RI) after the procedure were significantly different among the 3 groups (P=0.043), and the RDN group showed a greater reduction of RI than the control group (P=0.032) and sham group (P=0.043). Serum levels of eNOS, NO and Ang Ⅱ did not differ significantly among the groups either before or after RDN (P>0.05), but serum NE level was significantly higher in RDN group than in the control groupafter successful modeling (P=0.014), but similar to that in the sham group (P=0.560). Compared with the sham operation, RDN in the hypertensive beagles resulted in a significantly greater decrease of serum NE level (P=0.032) to almost the control level (P= 0.080). The changes of RI following RDN were significantly correlated with the changes of SBP, DBP and serum levels of NO and NE (P < 0.05).

CONCLUSION

RDN can significantly reduce blood pressure and improve arterial stiffness in hypertensive beagles possibly by reducing sympathetic activity and blood pressure and promoting NO synthesis.

Acute effects of long-distance races on heart rate variability and arterial stiffness: A systematic review and meta-analysis

This study systematically reviewed and quantified the effects of running a long-distance race (LDR) on heart rate variability (HRV) and arterial stiffness (AS). All types of races of a distance equal to or greater than a marathon (≥42.2 km) were included. A total of 2,220 articles were identified, 52 were included in the qualitative analysis, and 48 were meta-analysed. The standardised mean difference pre- and post-race of various time-domain and frequency-domain indices of HRV, mean arterial blood pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP) and carotid-femoral pulse wave velocity (cfPWV) was calculated. Regarding HRV, there was a significant decrease in most of the variables considered as markers of parasympathetic activity, indicating a shift of autonomic balance towards a reduced vagal tone. Regarding vascular variables, there was a significant drop in blood pressure and reduced AS. In conclusion, running an LDR seems to have a considerable acute effect on the autonomic nervous system, haemodynamics, and vascular properties. The observed effects could be categorised within the expected acute responses to long-lasting, strenuous exercise.

Assessment of Cerebrovascular Dynamics and Cognitive Function with Acute Aerobic Exercise in Persons with Multiple Sclerosis

Background

Cognitive dysfunction in multiple sclerosis (MS) may partially stem from inadequate cerebral blood flow. Cerebral blood flow and cognitive function improve with aerobic exercise in healthy adults. The effect of aerobic exercise on cerebrovascular hemodynamics and cognitive performance in persons with MS is unclear. The acute effect of aerobic exercise versus quiet rest on cerebrovascular hemodynamics and cognitive performance in relapsing-remitting MS was examined.

Methods

Sixteen adults with relapsing-remitting MS underwent cerebrovascular hemodynamics and cognitive performance testing before, 2 minutes after, and 30 minutes after aerobic exercise (20-minute treadmill walking, 60% peak oxygen consumption) and a time-matched seated control. Brachial blood pressure was obtained via an oscillometric cuff. Right middle cerebral artery (MCA) blood velocity was measured via transcranial Doppler and used to calculate mean velocity, pulsatility index (PI), and conductance. Carotid artery stiffness was measured via ultrasonography and tonometry. Cognitive performance (accuracy, reaction time) was assessed using a modified flanker task.

Results

Exercise elicited significant increases in mean pressure and carotid artery stiffness and decreases in MCA conductance at 2 minutes after exercise, which subsided by 30 minutes (P < .05). Exercise did not significantly alter MCA PI. Flanker reaction time decreased during posttesting in both conditions (P < .05). There were no condition × time interactions for cognitive performance.

Conclusions

Persons with MS seem resilient to exercise-induced acute changes in MCA PI despite transient carotid stiffening, potentially via reductions in MCA conductance. These data suggest that changes in cognitive performance after acute aerobic exercise are not directly related to transient cerebrovascular responses in persons with MS.

COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2

KEY POINTS

The impact of SARS-CoV-2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS-CoV-2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS-CoV-2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS-CoV-2 infection, there may be substantial adverse implications for cardiovascular health.

ABSTRACT

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can elicit systemic adverse physiological effects. However, the impact of SARS-CoV-2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS-CoV-2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head-up tilt (HUT). Data were compared with age-matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min-1 ) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min-1 ) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group-by-position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS-CoV-2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults.

Global REACH 2018: the adaptive phenotype to life with chronic mountain sickness and polycythaemia

KEY POINTS

Humans suffering from polycythaemia undergo multiple circulatory adaptations including changes in blood rheology and structural and functional vascular adaptations to maintain normal blood pressure and vascular shear stresses, despite high blood viscosity. During exercise, several circulatory adaptations are observed, especially involving adrenergic and non-adrenergic mechanisms within non-active and active skeletal muscle to maintain exercise capacity, which is not observed in animal models. Despite profound circulatory stress, i.e. polycythaemia, several adaptations can occur to maintain exercise capacity, therefore making early identification of the disease difficult without overt symptomology. Pharmacological treatment of the background heightened sympathetic activity may impair the adaptive sympathetic response needed to match local oxygen delivery to active skeletal muscle oxygen demand and therefore inadvertently impair exercise capacity.

ABSTRACT

Excessive haematocrit and blood viscosity can increase blood pressure, cardiac work and reduce aerobic capacity. However, past clinical investigations have demonstrated that certain human high-altitude populations suffering from excessive erythrocytosis, Andeans with chronic mountain sickness, appear to have phenotypically adapted to life with polycythaemia, as their exercise capacity is comparable to healthy Andeans and even with sea-level inhabitants residing at high altitude. By studying this unique population, which has adapted through natural selection, this study aimed to describe how humans can adapt to life with polycythaemia. Experimental studies included Andeans with (n = 19) and without (n = 17) chronic mountain sickness, documenting exercise capacity and characterizing the transport of oxygen through blood rheology, including haemoglobin mass, blood and plasma volume and blood viscosity, cardiac output, blood pressure and changes in total and local vascular resistances through pharmacological dissection of α-adrenergic signalling pathways within non-active and active skeletal muscle. At rest, Andeans with chronic mountain sickness had a substantial plasma volume contraction, which alongside a higher red blood cell volume, caused an increase in blood viscosity yet similar total blood volume. Moreover, both morphological and functional alterations in the periphery normalized vascular shear stress and blood pressure despite high sympathetic nerve activity. During exercise, blood pressure, cardiac work and global oxygen delivery increased similar to healthy Andeans but were sustained by modifications in both non-active and active skeletal muscle vascular function. These findings highlight widespread physiological adaptations that can occur in response to polycythaemia, which allow the maintenance of exercise capacity.

COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2

Key points

The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown.

For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects.

Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls.

Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis.

If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.

Abstract

The novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) can elicit systemic adverse physiological effects. However, the impact of SARS‐CoV‐2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS‐CoV‐2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head‐up tilt (HUT). Data were compared with age‐matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min⁻¹) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min⁻¹) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group‐by‐position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS‐CoV‐2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults.

The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown.

For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects.

Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls.

Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis.

If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.

Wearable Cuff-Less Blood Pressure Estimation at Home via Pulse Transit Time

OBJECTIVE

We developed a wearable watch-based device to provide noninvasive, cuff-less blood pressure (BP) estimation in an at-home setting.

METHODS

The watch measures single-lead electrocardiogram (ECG), tri-axial seismocardiogram (SCG), and multi-wavelength photoplethysmogram (PPG) signals to compute the pulse transit time (PTT), allowing for BP estimation. We sent our custom watch device and an oscillometric BP cuff home with 21 healthy subjects, and captured the natural variability in BP over the course of a 24-hour period.

RESULTS

After calibration, our Pearson correlation coefficient (PCC) of 0.69 and root-mean-square-error (RMSE) of 2.72 mmHg suggest that noninvasive PTT measurements correlate with around-the-clock BP. Using a novel two-point calibration method, we achieved a RMSE of 3.86 mmHg. We further demonstrated the potential of a semi-globalized adaptive model to reduce calibration requirements.

CONCLUSION

This is, to the best of our knowledge, the first time that BP has been comprehensively estimated noninvasively using PTT in an at-home setting. We showed a more convenient method for obtaining ambulatory BP than through the use of the standard oscillometric cuff. We presented new calibration methods for BP estimation using fewer calibration points that are more practical for a real-world scenario.

SIGNIFICANCE

A custom watch (SeismoWatch) capable of taking multiple BP measurements enables reliable remote monitoring of daily BP and paves the way towards convenient hypertension screening and management, which can potentially reduce hospitalizations and improve quality of life.

Association between household income and pulse pressure: data from the Korean National Health and Nutrition Examination Survey

PURPOSE

There has been limited evidence for the association between socioeconomic status (SES) and arterial stiffness. This study was performed to investigate the association between household income and brachial pulse pressure (PP) in the general Korean population.

MATERIALS AND METHODS

This study was based on data acquired in the 2018 Korea National Health and Nutrition Examination Survey (2018 KNHANES). A total of 13004 subjects at the age of 20 years or older analysed. The information on monthly household income was obtained through the questionnaire, and was stratified into 5 groups for each quintile. Brachial blood pressure (BP) was measured 3 times, and the average of the second and third measured BPs were used. PP was calculated as the difference between systolic and diastolic BPs.

RESULTS

A lower household income was associated with a higher prevalence of cardiovascular risk factors. As household income increased, PP decreased proportionally (p < .001). In multiple linear regression analysis, household income (per quintile) was independently associated with PP even after controlling for potential confounders (β = -.125, p < .001). Multiple binary logistic regression analysis showed that the increased household income level was significantly associated lower probability having higher PP (≥ 43.5 mmHg) even after controlling for multiple covariates (the lowest vs. the highest household income; odds ratio, 0.48; 95% confidence interval, .41-.55; p < .001).

CONCLUSION

Low household income was associated with higher PP. This provides additional evidence for the association between low SES and high arterial stiffness.

Arterial stiffness is not acutely modified by consumption of a caffeinated soft drink sweetened with high-fructose corn syrup in young healthy adults

We tested the hypothesis that ingestion of a caffeinated soft drink sweetened with high‐fructose corn syrup acutely increases arterial stiffness. In a randomized counterbalanced, crossover design, fourteen healthy adults (25 ± 3 years, 6 women) reported to the laboratory for two experimental visits where 500 ml of tap water (H₂O) or 500 ml of Mountain Dew® (a caffeinated soft drink sweetened with high‐fructose corn syrup (HFCS)) were consumed. Arterial stiffness (carotid‐to‐femoral pulse wave velocity (cfPWV)), peripheral and central blood pressures were measured pre‐consumption, 30 min post‐consumption, and 120 min post‐consumption. Prior to each measurement period, beat‐to‐beat hemodynamic measures were collected. Changes in heart rate, blood pressure, and cardiac output from pre‐consumption did not differ between trials at any timepoint (p ≥ 0.06). Moreover, changes in peripheral or central blood pressures from pre‐consumption did not differ between trials (p ≥ 0.84). Likewise, changes in cfPWV from pre‐consumption to 30 min post‐consumption (HFCS: 0.2 ± 0.3 m/s, H₂O: 0.0 ± 0.3 m/s, p = 0.34) and 120 min post‐consumption (HFCS: 0.3 ± 0.4 m/s, H₂O: 0.2 ± 0.3 m/s, p = 0.77) did not differ. Changes in aortic augmentation pressure, augmentation index, augmentation index corrected to a heart rate of 75 bpm, and reflection magnitude did not differ between conditions at 30 min post‐ (p ≥ 0.55) or 120 min post‐ (p ≥ 0.18) consumption. In healthy young adults, ingesting 500 ml of a commercially available caffeinated soft drink sweetened with high‐fructose corn syrup does not acutely change indices of arterial stiffness and wave reflection.

No Evidence That Hyperpnea-Based Respiratory Muscle Training Affects Indexes of Cardiovascular Health in Young Healthy Adults

Introduction

The chronic effects of respiratory muscle training (RMT) on the cardiovascular system remain unclear. This investigation tested to which degree a single sessions of RMT with or without added vibration, which could enhance peripheral blood flow and vascular response, or a 4-week RMT program could result in changes in pulse wave velocity (PWV), blood pressure (systolic, SBP; diastolic, DBP) and other markers of cardiovascular health.

Methods

Sixteen young and healthy participants (8 m/8f) performed 15 min of either continuous normocapnic hyperpnea (RMET), sprint-interval-type hyperpnea (RMSIT) or a control session (quiet sitting). Sessions were performed once with and once without passive vibration of the lower limbs. To assess training-induced adaptations, thirty-four young and healthy participants (17 m/17f) were measured before and after 4 weeks (three weekly sessions) of RMET (n = 13, 30-min sessions of normocapnic hyperpnea), RMSIT [n = 11, 6 × 1 min (1 min break) normocapnic hyperpnea with added resistance] or placebo (n = 10).

Results

SBP was elevated from baseline at 5 min after each RMT session, but returned to baseline levels after 15 min, whereas DBP was unchanged from baseline following RMT. Carotid-femoral PWV (PWV_CF) was elevated at 5 and 15 min after RMT compared to baseline (main effect of time, P = 0.001), whereas no changes were seen for carotid-radial PWV (PWV_CR) or the PWV_CF/PWV_CR ratio. Vibration had no effects in any of the interventions. Following the 4-week training period, no differences from the placebo group were seen for SBP (P = 0.686), DBP (P = 0.233), PWV_CF (P = 0.844), PWV_CR (P = 0.815) or the PWV_CF/PWV_CR ratio (P = 0.389).

Discussion/Conclusion

Although 15 min of RMT sessions elicited transient increases in PWV_CF and SBP, no changes were detected following 4 weeks of either RMET or RMSIT. Adding passive vibration of the lower limbs during RMT sessions did not provide additional value to the session with regards to vascular responses.

The effects of repeated binge drinking on arterial stiffness and urinary norepinephrine levels in young adults

OBJECTIVES

The aim of this study was to investigate the effect of repeated binge drinking and moderate alcohol consumption in young adults on arterial stiffness and sympathetic activity.

METHODS

We enrolled 49 healthy young adults, free of cardiovascular diseases (25 men; age: 23.5 ± 0.4 years; BMI: 23.4 ± 0.4 kg/m; mean ± S.E). Individuals included were those with a history of repeated binge drinking (>2 years duration; n = 20), drank at moderate levels (MODs, >5 years duration; n = 16) and abstained from alcohol (last 2-3 years; n = 13). Arterial stiffness was assessed using carotid to femoral pulse wave velocity (cfPWV) and sympathetic activity was assessed using 24-h urinary norepinephrine levels. Also measured was aortic SBP and augmentation index (AIx), a measure of wave reflection.

RESULTS

Binge drinkers and MODs had higher cfPWV than alcohol abstainers (0.6 and 0.5 m/s, respectively; P ≤ 0.04). In addition, binge drinkers had higher urinary norepinephrine levels than MODs and alcohol abstainers (P < 0.05). Higher cfPWV were correlated with higher norepinephrine levels (r = 0.35. P = 0.02). Aortic SBP (P = 0.2) and AIx (P = 0.96) were similar among binge drinkers, MODs and alcohol abstainers.

CONCLUSION

Our findings suggest that repeated exposure to alcohol, regardless of drinking pattern, may increase aortic arterial stiffness in healthy young adults. In addition, sympathetic activation, reflected by increased 24-h urinary norepinephrine levels, may contribute to alcohol-induced arterial stiffening in young adults.

Association of the Amount and Pattern of Physical Activity With Arterial Stiffness: The Maastricht Study

Background Arterial stiffness is an independent risk factor for cardiovascular disease and can be beneficially influenced by physical activity. However, it is not clear how an individual's physical activity pattern over a week is associated with arterial stiffness. Therefore, we examined the associations of the amount and pattern of higher intensity physical activity with arterial stiffness. Methods and Results Data from the Maastricht Study (n=1699; mean age: 60±8 years, 49.4% women, 26.9% type 2 diabetes mellitus) were used. Arterial stiffness was assessed by carotid-to-femoral pulse wave velocity and carotid distensibility. The amount (continuous variable as h/wk) and pattern (categorical variable) of higher intensity physical activity were assessed with the activPAL3. Activity groups were: inactive (<75 min/wk), insufficiently active (75-150 min/wk), weekend warrior (>150 min/wk in ≤2 sessions), and regularly active (>150 min/wk in ≥3 sessions). In the fully adjusted model (adjusted for demographic, lifestyle, and cardiovascular risk factors), higher intensity physical activity was associated with lower carotid-to-femoral pulse wave velocity (amount: β = -0.05, 95% CI, -0.09 to -0.01; insufficiently active: β = -0.33, 95% CI, -0.55 to -0.11; weekend warrior: β = -0.38, 95% CI, -0.64 to -0.12; and regularly active: β = -0.46, 95% CI, -0.71 to -0.21 [reference: inactive]). These associations were stronger in those with type 2 diabetes mellitus. There was no statistically significant association between higher intensity physical activity with carotid distensibility. Conclusions Participating in higher intensity physical activity was associated with lower carotid-to-femoral pulse wave velocity, but there was no difference between the regularly actives and the weekend warriors. From the perspective of arterial stiffness, engaging higher intensity physical activity, regardless of the weekly pattern, may be an important strategy to reduce the risk of cardiovascular disease, particularly in individuals with type 2 diabetes mellitus.

Sympathetic neural modulation of arterial stiffness in humans

Elevated large-artery stiffness is recognized as an independent predictor of cardiovascular and all-cause mortality. The mechanisms responsible for such stiffening are incompletely understood. Several recent cross-sectional and acute experimental studies have examined whether sympathetic outflow, quantified by microneurographic measures of muscle sympathetic nerve activity (MSNA), can modulate large-artery stiffness in humans. A major methodological challenge of this research has been the capacity to evaluate the independent neural contribution without influencing the dynamic blood pressure dependence of arterial stiffness. The focus of this review is to summarize the evidence examining 1) the relationship between resting MSNA and large-artery stiffness, as determined by carotid-femoral pulse wave velocity or pulse wave reflection characteristics (i.e., augmentation index) in men and women; 2) the effects of acute sympathoexcitatory or sympathoinhibitory maneuvers on carotid-femoral pulse wave velocity and augmentation index; and 3) the influence of sustained increases or decreases in sympathetic neurotransmitter release or circulating catecholamines on large-artery stiffness. The present results highlight the growing evidence that the sympathetic nervous system is capable of modulating arterial stiffness independent of prevailing hemodynamics and vasomotor tone.

Methodological considerations for the measurement of arterial stiffness using applanation tonometry

INTRODUCTION

Accurate comparisons of carotid--femoral pulse wave velocity (cfPWV) within and across studies require standardized procedures. Guidelines suggest reporting the average of at least two cfPWV measurements; if the difference exceeds 0.5 m/s, a third measurement should be taken, and the median reported. Another method involves repeating measurements until two values are within 0.5 m/s. However, in many studies, duplicate measurements are averaged irrespective of the difference between readings. We evaluated the impact of these methods on the reported cfPWV value.

METHODS

Measurements of cfPWV (SphygmoCor) from five studies included individuals spanning a wide age range, with or without comorbid conditions, and pregnant women. In participants with at least three high-quality measurements, differences between the median value (MED) and the average of the first two cfPWV measurements (AVG1) and the average of two cfPWV measurements within 0.5 m/s (AVG2) were evaluated using paired t-tests and Bland--Altman plots.

RESULTS

Participants' mean age was 50 ± 14 years and BMI was 28.0 ± 5.5 kg/m2 (N = 306, 79% women). The overall mean difference was -0.10 m/s (95% CI 0.17 to -0.04) between MED and AVG1, and 0.11 m/s (95% CI 0.05--0.17) between MED and AVG2. The absolute difference exceeded 0.5 m/s in 34% (MED-AVG1) and 22% (MED-AVG2) of participants, and 1 m/s in 8% of participants (both MED-AVG1 and MED-AVG2). Scatter around the bias line increased with higher mean cfPWV values.

CONCLUSION

Although the overall mean difference in cfPWV between protocols was not clinically relevant, large variation led to absolute differences exceeding 0.5 m/s in a large proportion of participants.

Autonomic Phenotypes in Chronic Fatigue Syndrome (CFS) Are Associated with Illness Severity: A Cluster Analysis

In this study we set out to define the characteristics of autonomic subgroups of patients with Chronic Fatigue Syndrome (CFS). The study included 131 patients with CFS (Fukuda criteria). Participants completed the following screening symptom assessment tools: Chalder Fatigue Scale, Fatigue Impact Scale, Fatigue Severity Scale, Epworth Sleepiness Scales, the self-reported Composite Autonomic Symptom Scale. Autonomic parameters were measured at rest with a Task Force Monitor (CNS Systems) and arterial stiffness using an Arteriograph (TensioMed Kft.). Principal axis factor analysis yielded four factors: fatigue, subjective and objective autonomic dysfunction and arterial stiffness. Using cluster analyses, these factors were grouped in four autonomic profiles: 34% of patients had sympathetic symptoms with dysautonomia, 5% sympathetic alone, 21% parasympathetic and 40% had issues with sympathovagal balance. Those with a sympathetic-dysautonomia phenotype were associated with more severe disease, reported greater subjective autonomic symptoms with sympathetic over-modulation and had the lowest quality of life. The highest quality of life was observed in the balance subtype where subjects were the youngest, had lower levels of fatigue and the lowest values for arterial stiffness. Future studies will aim to design autonomic profile-specific treatment interventions to determine links between autonomic phenotypes CFS and a specific treatment.

Relationship of Socioeconomic Status to Arterial Stiffness: Comparison Between Medical Aid Beneficiaries and National Health Insurance Beneficiaries

BACKGROUND

There is no general agreement on underlying pathophysiology explaining the high burden of cardiovascular disease on people at low socioeconomic status (SES). This study was conducted to investigate the association between healthcare systems and arterial stiffness.

METHODS

A total of 8,929 subjects (60 years old and 55% were male) who underwent brachial-ankle pulse wave velocity (baPWV) measurement were retrospectively analyzed. There were 8,237 National Health Insurance (NHI) beneficiaries (92.2%) and 692 medical aid (MA) beneficiaries (7.8%). The median value of baPWV was 1,540 cm/s.

RESULTS

Subjects with higher baPWV values (≥1,540 cm/s) were older, and more frequently had cardiovascular risk factors and unfavorable laboratory findings than those with lower values baPWV (<1,540 cm/s). The baPWV values were significantly higher in MA beneficiaries than in NHI beneficiaries (1,966 ± 495 vs. 1,582 ± 346 cm/s, P < 0.001). The proportion of MA beneficiaries was significantly higher in subjects with higher baPWV than those with lower baPWV (13.1% vs. 2.3%, P < 0.001). In multivariable analysis, MA beneficiaries were significantly associated with higher baPWV values even after controlling for potential confounders (odds ratio, 5.41; 95% confidence intervals, 4.02-7.27; P < 0.001).

CONCLUSIONS

The baPWV values were significantly higher in MA beneficiaries than in NHI beneficiaries. The result of this study provides additional evidence on the association between low SES and arterial stiffening.

Repeatability and reproducibility of pulse wave velocity in relation to hemodynamics and sodium excretion in stable patients with hypertension

OBJECTIVE

Pulse wave velocity (PWV) is a useful marker for determining subclinical vascular damage and patient risk stratification. Repeatability and reproducibility of PWV in relation to influencing factors have not yet been determined. This study examined the repeatability and reproducibility of PWV, and whether hemodynamics and sodium excretion impact on PWV in hypertensive patients remaining on stable medication.

METHODS

Office blood pressure (BP), heart rate (HR), carotid--femoral PWV and central BP (SphygmoCor device), impedance cardiography (HOTMAN device) and 24-h urinary sodium excretion (UNa) were measured at baseline and after 4 weeks in 74 hypertensive patients (age 56.8 ± 11.5 years, mean ± SD). Two PWV measurements were performed at each visit.

RESULTS

Intraclass correlation coefficient (ICC) and 95% confidence interval (95% CI) between the two PWV measurements were 0.981 (0.970--0.988) at baseline, 0.975 (0.960--0.984) after 4 weeks and 0.851 (0.773--0.903) between both visits. There were no significant changes in BP, HR, thoracic fluid content, stroke volume and UNa between visits. Despite excellent ICC, reproducibility of PWV was related to BP (P < 0.001) and HR (P = 0.07) changes between visits. Nineteen out of 74 patients had a difference in PWV greater than ±1 m/s between both visits.

CONCLUSION

In the medium-term observation, changes in BP and HR seem to affect PWV values. Our findings suggest that the assessment of PWV should be performed under stabilized BP and HR values, particularly in patients with newly diagnosed hypertension and/or low--moderate cardiovascular risk in whom the detection of asymptomatic hypertension-mediated organ damage impact on patient risk stratification.

Vascular Decoupling in Septic Shock: The Combined Role of Autonomic Nervous System, Arterial Stiffness, and Peripheral Vascular Tone

BACKGROUND

Acute inflammation and sepsis are known to induce changes in vascular properties, leading to increased arterial stiffness; at the same time, the autonomic nervous system (ANS) also affects vascular properties by modulating the arterial smooth muscle tone, and it is widely reported that sepsis and septic shock severely impair ANS activity. Currently, clinical guidelines are mainly concerned to resuscitate septic shock patients from hypotension, hypovolemia, and hypoperfusion; however, if the current resuscitation maneuvers have a beneficial effect also on vascular properties and autonomic functionality is still unclear. The objective of this work is to assess the effects of standard resuscitation at vascular level and to verify if there is any association between alterations in vascular properties and ANS activity.

METHODS

Six pigs underwent a protocol of polymicrobial septic shock and resuscitation (fluids and noradrenaline). The arterial blood pressure (ABP) waveform was recorded in the central aorta and in the peripheral radial and femoral artery. The characteristic arterial time constant was computed at the three arterial sites based on the two-element Windkessel model, to characterize the overall arterial vascular tree. Moreover, independent estimates of total arterial compliance (AC) and total peripheral resistance (TPR) were performed. Baroreflex sensitivity (BRS), low frequency (LF, 0.04-0.15 Hz) spectral power of diastolic blood pressure, and indices of heart rate variability (HRV) were computed to assess ANS functionality.

RESULTS

Septic shock induced a severe vascular disarray, decoupling the usual pressure wave propagation from central to peripheral sites; this phenomenon appeared as an inversion of the physiological pulse pressure (PP) amplification, with a higher PP in the central aorta than in the peripheral arteries. The time constant was decreased, together with AC and TPR. ANS dysfunction was described by a reduced BRS, decreased LF power, and suppressed HRV. This compromised condition was not resolved by administration of fluids and noradrenaline. Thus, a persistent vascular and autonomic dysfunction were reported also in the resuscitated animals, and they were found to be significantly correlated.

CONCLUSION

Measures of vascular function and ANS activity could add information to standard hemodynamic and clinical markers, and the current resuscitation strategies could benefit from the adjunction of these additional functional indices.

Acute psychological stress, autonomic function, and arterial stiffness among women

This study aimed to investigate the effect of acute psychological stress on autonomic function and arterial stiffness, and to test a mediating role of changes in autonomic function between acute stress and arterial stiffness. Eighty-five healthy female adults were randomized into either an experimental or control group. The Trier Social Stress Test (TSST) was used to induce acute psychological stress. Autonomic function (measured by pre-ejection period [PEP] from cardiac impedance and high frequency [HF] of heart rate variability [HRV]) and arterial stiffness (measured by carotid and femoral pulse wave velocity [cfPWV] and augmentation index [AIx]) were assessed before and after the TSST. The mean age of the participants was 28.78 (±9.84) years old. Experimental group participants had a significant increase in cfPWV (p = .025) and AIx (p = .017) following the stressor, compared with those in the control group, after controlling for age, body mass index, and systolic blood pressure. However, no significant group differences were observed in changes in PEP (p = .181) and HF (p = .058). Changes in PEP and HF were neither associated with changes in cfPWV (p = .975 and p = .654, respectively), nor in AIx (p = .376 and p = .323, respectively). The results suggest that even a brief period of mild to moderate stress, which does not cause sustainable changes in autonomic function, may still exert significant adverse effects on arterial stiffness. The changes in arterial stiffness were not related to changes in autonomic function. Future experimental studies with several measurement points are recommended to identify distinct effects of stress on autonomic function and arterial stiffness.

Global REACH 2018: Andean highlanders, chronic mountain sickness and the integrative regulation of resting blood pressure

NEW FINDINGS

What is the central question of this study? Does chronic mountain sickness (CMS) alter sympathetic neural control and arterial baroreflex regulation of blood pressure in Andean (Quechua) highlanders? What is the main finding and its importance? Compared to healthy Andean highlanders, basal sympathetic vasomotor outflow is lower, baroreflex control of muscle sympathetic nerve activity is similar, supine heart rate is lower and cardiovagal baroreflex gain is greater in mild CMS. Taken together, these findings reflect flexibility in integrative regulation of blood pressure that may be important when blood viscosity and blood volume are elevated in CMS.

ABSTRACT

The high-altitude maladaptation syndrome chronic mountain sickness (CMS) is characterized by excessive erythrocytosis and frequently accompanied by accentuated arterial hypoxaemia. Whether altered autonomic cardiovascular regulation is apparent in CMS is unclear. Therefore, during the 2018 Global REACH expedition to Cerro de Pasco, Peru (4383 m), we assessed integrative control of blood pressure (BP) and determined basal sympathetic vasomotor outflow and arterial baroreflex function in eight Andean natives with CMS ([Hb] 22.6 ± 0.9 g·dL^-1 ) and seven healthy highlanders ([Hb] 19.3 ± 0.8 g·dL^-1 ). R-R interval (RRI, electrocardiogram), beat-by-beat BP (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded at rest and during pharmacologically induced changes in BP (modified Oxford test). Although [Hb] and blood viscosity (7.8 ± 0.7 vs. 6.6 ± 0.7 cP; d = 1.7, P = 0.01) were elevated in CMS compared to healthy highlanders, cardiac output, total peripheral resistance and mean BP were similar between groups. The vascular sympathetic baroreflex MSNA set-point (i.e. MSNA burst incidence) and reflex gain (i.e. responsiveness) were also similar between groups (MSNA set-point, d = 0.75, P = 0.16; gain, d = 0.2, P = 0.69). In contrast, in CMS the cardiovagal baroreflex operated around a longer RRI (960 ± 159 vs. 817 ± 50 ms; d = 1.4, P = 0.04) with a greater reflex gain (17.2 ± 6.8 vs. 8.8 ± 2.6 ms·mmHg^-1 ; d = 1.8, P = 0.01) versus healthy highlanders. Basal sympathetic vasomotor activity was also lower compared to healthy highlanders (33 ± 11 vs. 45 ± 13 bursts·min^-1 ; d = 1.0, P = 0.08). In conclusion, our findings indicate adaptive differences in basal sympathetic vasomotor activity and heart rate compensate for the haemodynamic consequences of excessive erythrocyte volume and contribute to integrative blood pressure regulation in Andean highlanders with mild CMS.

Single-pill combination of cilnidipine, an L-/N-type calcium channel blocker, and valsartan effectively reduces home pulse pressure in patients with uncontrolled hypertension and sympathetic hyperactivity: The HOPE-Combi survey

The home blood pressure (BP) control by a single-pill combination of cilnidipine (an L-/N-type calcium channel blocker; CCB) and valsartan (HOPE-Combi) survey is a multicenter, post-marketing, prospective observational study of a single-pill combination of cilnidipine 10 mg and valsartan 80 mg (SPC of Cil/Val) in patients with uncontrolled hypertension. We examined the effects of the SPC of Cil/Val on morning home systolic BP (MHSBP) and morning home pulse pressure (MHPP) of 1036 patients with hypertension over 12 months. MHSBP decreased by 14.0 mm Hg (P < .01), and MHPP decreased by 6.6 mm Hg (P < .01). Moreover, morning home pulse rate (MHPR) decreased by 2.1 bpm (P < .01). A more progressive and greater decrease in MHSBP (-17.2 vs -10.3 mm Hg, P < .01) and MHPP (-7.6 vs -4.9 mm Hg, P < .01) was observed in patients with higher MHPR (≥70 bpm) than in those with lower MHPR (<70 bpm) over the treatment period. In particular, in patients with a wide MHPP (≥70 mm Hg), the difference in the MHPP reduction was greater in patients with higher MHPR than in those with lower MHPR (-17.9 vs -13.6 mm Hg, P < .01). These results suggested that the SPC of Cil/Val, which possesses the unique sympatholytic characteristics of an L-/N-type CCB, was particularly effective in patients with uncontrolled hypertension and sympathetic hyperactivity.

The Effect of Body Position on Measures of Arterial Stiffness in Humans

BACKGROUND

The dynamics ofpulsatile waveforms travelling the central aorta are governed by pressures and arterial compliance. Arterial stiffness, the inverse of compliance, is an independent risk factor for cardiovascular disease and has been suggested as a superior risk index compared to brachial blood pressure (BP). Arterial stiffness is typically measured via carotid-femoral pulse wave velocity (cfPWV) in the supine position; however, different body positions alter orthostatic column height, impacting heart rate and BP. The purpose of this investigation was to examine different body positions and associated measures of cfPWV.

METHODS

Measures of resting cfPWV were acquired simultaneously with BP during supine, head-up tilt (HUT), head-down tilt (HDT), and Fowler's position, all at 45 degrees from vertical.

RESULTS

Relative to supine, cfPWV was increased 1.1 ± 1.0 and 1.5 ± 1.1 m/s (both p ≤ 0.001) in HUT and Fowler's positions, respectively. Supine to HDT cfPWV was unaltered (p = 0.1), despite an increase in mean arterial pressure (MAP) (10 ± 9 mm Hg). When cfPWV was normalized to MAP, the same effects persisted (p ≤ 0.001).

CONCLUSION

Increasing orthostatic column height by changing posture independently increases resting cfPWV, concurrent with increases in BP. This data demonstrates the impact of body position on measures of central artery stiffness, which may have clinical relevance.

A recent history of preeclampsia is associated with elevated central pulse wave velocity and muscle sympathetic outflow

We demonstrate that resting muscle sympathetic nerve activity is elevated in women with a recent history of preeclampsia relative to women who have recently had uncomplicated pregnancies and without a history of preeclampsia. Structural changes in the central arteries are associated with arterial stiffness following preeclampsia, independent of changes in the sympathetic nervous system. The structural changes are observed in these relatively young previously preeclamptic women, indicating elevated cardiovascular risk. Our data suggest that with aging (and the gradual loss of vascular protection for women, as established by others), this risk will become exaggerated compared with women who have had normal pregnancies.

Photoplethysmography Detection of Overreaching

INTRODUCTION

Detecting the onset of functional overreaching (FOR) or nonfunctional overreaching in endurance athletes is of prior importance to ensure reactive amendment of the scheduled training program. The objective of this study was to assess photoplethysmography (PPG) in overloaded athletes and test whether 1) it would be affected differently in functional overreached (FOR) or nonoverreached acutely fatigued (AF) athletes and 2) specific PPG characteristics would allow for timely distinction of FOR and AF.

METHODS

Fifteen athletes performed 2-wk baseline training followed by 3-wk overload (+45%; OVL) and 2-wk recovery (-20%). Three-thousand-meter time-trial running was used to assess performance at the end of baseline, OVL, and recovery and distinguish FOR and AF. PPG was recorded overnight using a wearable sensor, every third night. Overnight means and variances of systolic, diastolic, and dicrotic amplitudes and times as well as systolic and diastolic slopes were used to discriminate FOR and AF athletes.

RESULTS

Performance was decreased in FOR and improved in AF at the end of OVL. Diastolic time was greater in AF than FOR, whereas systolic slope was smaller in AF than in FOR during OVL. The variances of systolic, diastolic, dicrotic amplitudes, systolic, diastolic slopes, and pulse areas were smaller in AF compared with FOR in the last week of OVL.

CONCLUSION

PPG is an efficient tool for the detection of overreaching because it distinguished FOR and AF athletes during OVL (prior performance decrement). This fast-responding method would therefore allow for adjusting the daily training content to prevent nonfunctional overreaching.

Elevated Muscle Sympathetic Nerve Activity Contributes to Central Artery Stiffness in Young and Middle-Age/Older Adults

Muscle sympathetic nerve activity (MSNA) influences the mechanical properties (ie, vascular smooth muscle tone and stiffness) of peripheral arteries, but it remains controversial whether MSNA contributes to stiffness of central arteries, such as the aorta and carotids. We examined whether elevated MSNA (age-related) would be independently associated with greater stiffness of central (carotid-femoral pulse wave velocity [PWV]) and peripheral (carotid-brachial PWV) arteries, in addition to lower carotid compliance coefficient, in healthy men and women (n=88, age: 19-73 years, 52% men). We also examined whether acute elevations in MSNA without increases in mean arterial pressure using graded levels of lower body negative pressure would augment central and peripheral artery stiffness in young (n=15, 60% men) and middle-age/older (MA/O, n=14, 43% men) adults. Resting MSNA burst frequency (bursts·min^-1) was significantly correlated with carotid-femoral PWV ( R=0.44, P<0.001), carotid-brachial PWV ( R=0.32, P=0.004), and carotid compliance coefficient ( R=0.28, P=0.01) after controlling for sex, mean arterial pressure, heart rate, and waist-to-hip ratio (central obesity), but these correlations were abolished after further controlling for age (all P>0.05). In young and MA/O adults, MSNA was elevated during lower body negative pressure ( P<0.001) and produced significant increases in carotid-femoral PWV (young: Δ+1.3±0.3 versus MA/O: Δ+1.0±0.3 m·s^-1, P=0.53) and carotid-brachial PWV (young: Δ+0.7±0.3 versus MA/O: Δ+0.7±0.5 m·s^-1, P=0.92), whereas carotid compliance coefficient during lower body negative pressure was significantly reduced in young but not MA/O (young: Δ-0.04±0.01 versus MA/O: Δ0.001±0.008 mm²·mm Hg^-1, P<0.01). Collectively, these data demonstrate the influence of MSNA on central artery stiffness and its potential contribution to age-related increases in stiffness of both peripheral and central arteries.

Interrelationships between pulse arrival time and arterial blood pressure during postural transitions before and after spaceflight

We tested the hypothesis that acute changes in arterial blood pressure (BP) when astronauts moved between supine and standing posture before and after spaceflight can be tracked by beat-to-beat changes in pulse arrival time (PAT). Nine male crewmembers (45 ± 7 yr of age; mean mission length: 165 ± 13 days) participated in a standardized supine-to-sit-to-stand test (5 min-30 s-3 min) before flight and 1 day following return to Earth with continuous monitoring of ECG and finger arterial BP. PAT was determined from the R-wave of the ECG to the foot of the BP waveform. On average, modest cardiovascular deconditioning was detected by ~10 beats/min increase in heart rate in supine and standing posture after spaceflight (P < 0.05). When looking across the full data collection period, the r² values between inverse of PAT (1/PAT) and systolic (SBP) and diastolic BP (DBP) varied considerably between individuals (SBP preflight 0.142 ± 0.186, postflight 0.262 ± 0.243). Individual variability was consistent during periods of transition (SBP preflight 0.284 ± 0.324, postflight 0.297 ± 0.269); however, when SBP dropped >20 mmHg, r² was significant in 5 of 5 preflight tests and 5 of 7 postflight tests. The standard error of the estimate based on a simple linear model during both pre- and postflight testing was 9-11 mmHg for SBP and 6-7 mmHg for DBP. Overall, the results support the hypothesis that PAT tracked dynamic changes in BP. PAT as a noninvasive, nonintrusive surrogate for changes in BP could be developed as an indicator of risk for syncope on return from spaceflight or other Earth-based applications.NEW & NOTEWORTHY Astronauts returning to Earth's gravity are at increased risk of low blood pressure on standing. Arterial pulse arrival time tracked the decrease in arterial blood pressure on moving from supine to upright posture. Nonintrusive technology providing indicators sensitive to acute changes in blood pressure could act as an early warning system to identify risk for hypotension that place astronauts, or people on Earth, at risk of impaired cognitive performance, fainting, and falls.

Arterial Stiffness Can Be Modulated by Pressure-Independent Mechanisms in Hypertension

Background Effects of short-term interventions on large-artery stiffness assessed by pulse wave velocity (PWV) have mainly been explained by concomitant changes in blood pressure (BP). However, lower body negative pressure, which increases sympathetic activity and has other hemodynamic effects, has a specific effect on PWV in healthy volunteers. Methods and Results We examined effects of lower-limb venous occlusion (LVO), a similar intervention to lower-body negative pressure that reduces BP but increases sympathetic activity and device-guided breathing (DGB), which reduces both BP and sympathetic activity, on PWV in patients with essential hypertension (n=70 after LVO, n=45 after DGB and LVO in random order). The short-acting calcium channel antagonist nifedipine was used as a control for changes in BP. LVO produced a small but significant reduction in mean arterial pressure of 1.8 (95% CI 0.3-3.4) mm Hg. Despite this, aortic and carotid-femoral PWV increased during LVO by 0.8 (0.2-1.4) m/s and 0.7 (0.3-1.05) m/s, respectively. DGB reduced PWV by 1.2 (0.9-1.4) m/s, to a greater extent than did nifedipine 10 mg (reduction of 0.7 [0.1-1.3] m/s, P<0.05 compared with reduction during DGB). This occurred despite a greater decrease in BP with nifedipine compared with DGB. Conclusions Arterial stiffness can be modulated independently of BP over the short term. The mechanism could involve alterations in sympathetic activity or other as yet uncharacterized effects of LVO and DGB.

Effects of acute aerobic exercise on arterial stiffness and cerebrovascular pulsatility in adults with and without hypertension

OBJECTIVES

Stiffer central arteries, as seen in hypertension (HTN), foster transmission of pulsatile hemodynamics into fragile cerebral vessels. Aerobic exercise is recommended for adults with HTN, but its effects on arterial stiffness and pulsatility in this group are unclear. This study sought to investigate the effect of acute aerobic exercise on arterial stiffness and cerebrovascular pulsatility in 30 adults with treated HTN and 30 age, sex, and BMI-matched adults without HTN (56 ± 6 years, BMI 28.2 ± 2.9 kg/m; 28 women).

METHODS

Patients underwent hemodynamic measures before/after 30-min cycling (≈55% peak oxygen consumption). Aortic stiffness was measured using carotid-femoral pulse wave velocity, and carotid artery stiffness was assessed with β-stiffness via ultrasound. Aortic/carotid pulse pressure (aortic via radial generalized transfer function) was measured by tonometry and calibrated to brachial mean pressure and diastolic pressure. Carotid/middle cerebral artery (MCA) blood velocity pulsatility indices were measured using Doppler. Carotid wave intensity analysis was used to derive forward wave intensity (W1).

RESULTS

Exercise impacted hemodynamics similarly in HTN compared to no-HTN. Carotid-femoral pulse wave velocity, MCA pulsatility index, carotid pulsatility index, and W1 increased similarly after exercise in both groups (P < 0.05). Carotid pulse pressure and β-stiffness were unaltered after exercise. Postexercise changes in W1 were positively associated with carotid pulsatility index, which was further associated with MCA pulsatility index.

CONCLUSIONS

These data suggest adults with treated HTN experience similar increases in aortic stiffness and cerebrovascular hemodynamic pulsatility during early recovery from acute aerobic exercise as their counterparts without HTN.

A multilocus genetic risk score is associated with arterial stiffness in hypertensive patients: the CARE NORTH study

INTRODUCTION

Arterial stiffness is recognized as an intermediate phenotype and predictor of cardiovascular disease. Arterial stiffness is complex in origin with contributions from lifestyle and genetic factors. However, the association between single nucleotide polymorphisms (SNPs) and arterial stiffness remains unclear.

OBJECTIVE

The aim is to assess whether a multilocus genetic risk score (GRS), composed of selected SNPs linked to cardiovascular traits and outcomes, is associated with arterial stiffness in patients with hypertension.

DESIGN AND METHODS

This study included 730 participants derived from the CARE NORTH study. The arterial stiffness was evaluated by carotid-femoral pulse wave velocity (cfPWV). An adjusted linear regression was used to evaluate the association between cfPWV and each individual SNP using multiple genetic models. The association between a constructed GRS and cfPWV was tested in an unadjusted and adjusted model.

RESULTS

We selected 13 SNPs found to be associated with cfPWV (P < .05): 6 SNPs in additive, 4 SNPs in recessive and 3 SNPs in dominant mode of inheritance. The GRS based on these SNPs was positively associated with cfPWV both in unadjusted and adjusted models (β = 0.2 m/s, 95% CI 0.11 - 0.29, P = 7.6 × 10 and β = 0.22 m/s, 95% CI 0.15 - 0.28, P = 1.4 × 10, respectively). The GRS explained an additional 3.6% cfPWV variance above clinical covariates.

CONCLUSION

We demonstrate that the GRS composed of 13 SNPs related to cardiovascular phenotypes is associated with an increased arterial stiffness in hypertensive patients. Our findings may help to clarify genetic basis of arterial stiffening and provide insight into mechanisms underlying this phenotype.

Age-Associated Differences in Central Artery Responsiveness to Sympathoexcitatory Stimuli

BACKGROUND

Age-associated arterial stiffening may be the result of greater tonic sympathetic nerve activity. However, age-associated changes in central artery responsiveness to sympathoexcitatory stimuli are understudied. Therefore, we examined changes in central artery stiffness and wave reflection in response to sympathoexcitatory stimuli in young and older adults.

METHODS

Fourteen young (25 ± 4 years) and 15 older (68 ± 4 years) subjects completed 3 minutes of the cold pressor test (CPT) and lower-body negative pressure (LBNP) separated by 15 minutes. Carotid-femoral pulse wave velocity (cfPWV), central augmentation pressure (cAP), and augmentation index (AIx) were measured in duplicate during rest and the final minute of each perturbation.

RESULTS

Young subjects had lower baseline cfPWV, cAP, and AIx than older subjects (P < 0.05 for all). During the CPT mean arterial pressure (MAP), cfPWV, cAP, and AIx increased in both groups (P < 0.05 for all); however, changes (Δ) in MAP (18 ± 7 vs. 9 ± 5 mm Hg), cfPWV (1.3 ± 0.7 vs. 0.6 ± 0.9 m/s), cAP (4 ± 2 vs. 6 ± 3 mm Hg), and AIx (18 ± 9% vs. 7 ± 4%) were greater in young vs. older subjects, respectively (P < 0.05 for all). With MAP as a covariate, cfPWV, cAP, and AIx responses to the CPT were no longer significantly different between groups. During LBNP, changes in MAP (-1 ± 3 vs. -3 ± 5 mm Hg), cfPWV (0.5 ± 0.3 vs. 0.5 ± 0.7 m/s), cAP (-2 ± 2 vs. -2 ± 3 mm Hg), and AIx (-7 ± 7% vs. -3 ± 6%) were similar between young and older groups, respectively (P > 0.05 for all).

CONCLUSIONS

Collectively, our data suggest the sympathetic nervous system may directly modulate central hemodynamics and that age-associated differences in central artery responsiveness to sympathoexcitatory stimuli are largely attributable to differential blood pressure responses.

Arterial stiffness during whole-body passive heat stress in healthy older adults

We tested the hypothesis that whole-body passive heat stress reduces arterial stiffness in older adults. At preheat stress (baseline) and when core temperature was elevated by 0.6 ± 0.2°C (mild) and 1.2 ± 0.3°C (moderate), arterial stiffness was measured in eight healthy younger (26 ± 5 years) and eight healthy older (70 ± 4 years) adults in the supine position. Arterial stiffness was estimated from carotid-to-femoral pulse wave velocity (cfPWV, applanation tonometry). cfPWV was higher at baseline in older adults (8.8 ± 2.3 m/sec vs. 5.6 ± 0.9 m/sec, P < 0.01) and this difference was maintained throughout passive heat stress (P < 0.01). cfPWV did not change (P ≥ 0.49) with passive heat stress in either younger (at moderate heat stress: 6.0 ± 1.0 m/sec) or older (at moderate heat stress: 8.5 ± 1.6 m/sec) adults. However, the influence of baseline cfPWV on the change in cfPWV during mild (r = -0.66, P = 0.04) and moderate (r = -0.87, P < 0.01) heat stress were inversely related in older adults, and the strength of these relations was not statistically different (P = 0.08). In younger adults, the influence of baseline cfPWV on the change in cfPWV during mild heat stress was also inversely related (r = -0.79, P = 0.01), while the strength of this relation was attenuated at moderate heat stress (r = -0.24, P = 0.30). Changes in arterial stiffness during passive heat stress in adults aged ≥65 year are likely dependent on the magnitude of baseline arterial stiffness and not necessarily age.