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.

Formulas to Explain Popular Oscillometric Blood Pressure Estimation Algorithms

Oscillometry is the blood pressure (BP) measurement principle of most automatic cuff devices. The oscillogram (which is approximately the blood volume oscillation amplitude-external pressure function) is measured, and BP is then estimated via an empirical algorithm. The objective was to establish formulas to explain three popular empirical algorithms in the literature—the maximum amplitude, derivative, and fixed ratio algorithms. A mathematical model of the oscillogram was developed and analyzed to derive parametric formulas for explaining each algorithm. Exemplary parameter values were obtained by fitting the model to measured oscillograms. The model and formulas were validated by showing that their predictions correspond to measurements. The formula for the maximum amplitude algorithm indicates that it yields a weighted average of systolic and diastolic BP (0.45 and 0.55 weighting) instead of commonly assumed mean BP. The formulas for the derivative algorithm indicate that it can accurately estimate systolic and diastolic BP (<1.5 mmHg error), if oscillogram measurement noise can be obviated. The formulas for the fixed ratio algorithm indicate that it can yield inaccurate BP estimates, because the ratios change substantially (over a 0.5–0.6 range) with arterial compliance and pulse pressure and error in the assumed ratio translates to BP error via large amplification (>40). The established formulas allow for easy and complete interpretation of perhaps the three most popular oscillometric BP estimation algorithms in the literature while providing new insights. The model and formulas may also be of some value toward improving the accuracy of automatic cuff BP measurement devices.

Evaluation of the calculation formulas of the cardio-ankle vascular index used in the Japanese apparatus

Background

Recently, coefficients in the equation of cardio-ankle vascular index (CAVI) used in VaSera^® device were disclosed. This study aimed to simulate the influence of adjusting the coefficients in the equation of CAVI and also aimed to validate the equation.

Methods

The CAVI displayed by VaSera (CAVIvs) and the CAVI estimated (CAVIes) with fixing the coefficients of the middle range of the heart-ankle stiffness parameter β (haβ) in the equation were compared. Moreover, the heart-ankle pulse wave velocity (haPWV) which corresponds to the low cutoff haβ of 7.348 was estimated in various blood pressure patterns to validate the formula.

Results

The CAVIvs was clearly lower than CAVIes in the low and the high range of CAVIvs. Moreover, it was virtually impossible to obtain the low cutoff haβ of 7.348 by using typical values of haPWV.

Conclusion

The CAVIvs in the high-range of VaSera underestimates the original property of stiffness parameter β. Moreover, there will be also a missing information in the equations introduced in the corresponding article, especially in the calculation formula of CAVIvs from haβ. Therefore, in order to make the best use of the nature of the stiffness parameter β to be used in VaSera, fixing the coefficients or termination of its use should be considered.

Acute Blood Pressure and Cardiovascular Effects of Near-Roadway Exposures With and Without N95 Respirators

BACKGROUND

The risk for cardiovascular events increases within hours of near-roadway exposures. We aimed to determine the traffic-related air pollution (TRAP) and biological mechanisms involved and if reducing particulate matter <2.5 µm (PM2.5) inhalation is protective.

METHODS

Fifty healthy-adults underwent multiple 2-hour near-roadway exposures (Tuesdays to Fridays) in Ann Arbor during 2 separate weeks (randomized to wear an N95 respirator during 1 week). Monday both weeks, participants rested 2 hours in an exam room (once wearing an N95 respirator). Brachial blood pressure, aortic hemodynamics, and heart rate variability were repeatedly measured during exposures. Endothelial function (reactive hyperemia index [RHI]) was measured post-exposures (Thursdays). Black carbon (BC), total particle count (PC), PM2.5, noise and temperature were measured throughout exposures.

RESULTS

PM2.5 (9.3 ± 7.7 µg/m3), BC (1.3 ± 0.6 µg/m3), PC (8,375 ± 4,930 particles/cm3) and noise (69.2 ± 4.2 dB) were higher (P values <0.01) and aortic hemodynamic parameters trended worse while near-roadway (P values<0.15 vs. exam room). Other outcomes were unchanged. Aortic hemodynamics trended towards improvements with N95 respirator usage while near-roadway (P values<0.15 vs. no-use), whereas other outcomes remained unaffected. Higher near-roadway PC and BC exposures were associated with increases in aortic augmentation pressures (P values<0.05) and trends toward lower RHI (P values <0.2). N95 respirator usage did not mitigate these adverse responses (nonsignificant pollutant-respirator interactions). Near-roadway outdoor-temperature and noise were also associated with cardiovascular changes.

CONCLUSIONS

Exposure to real-world combustion-derived particulates in TRAP, even at relatively low concentrations, acutely worsened aortic hemodynamics. Our mixed findings regarding the health benefits of wearing N95 respirators support that further studies are needed to validate if they adequately protect against TRAP given their growing worldwide usage.

Burden of Cardiovascular Risk Factors Over Time and Arterial Stiffness in Youth With Type 1 Diabetes Mellitus: The SEARCH for Diabetes in Youth Study

Background The incidence of type 1 diabetes mellitus (T1DM) in children is increasing, resulting in higher burden of cardiovascular diseases due to diabetes mellitus-related vascular dysfunction. Methods and Results We examined cardiovascular risk factors ( CVRF s) and arterial parameters in 1809 youth with T1DM. Demographics, anthropometrics, blood pressure, and laboratory data were collected at T1DM onset and 5 years later. Pulse wave velocity and augmentation index were collected with tonometry. ANOVA or chi-square tests were used to test for differences in measures of arterial parameters by CVRF . Area under the curve of CVRF s was entered in general linear models to explore determinants of accelerate vascular aging. Participants at the time of arterial measurement were 17.6±4.5 years old, 50% female, 76% non-Hispanic white, and duration of T1DM was 7.8±1.9 years. Glycemic control was poor (glycated hemoglobin, 9.1±1.8%). All arterial parameters were higher in participants with glycated hemoglobin ≥9% and pulse wave velocity was higher with lower insulin sensitivity or longer duration of diabetes mellitus. Differences in arterial parameters were found by sex, age, and presence of obesity, hypertension, or dyslipidemia. In multivariable models, higher glycated hemoglobin, lower insulin sensitivity, body mass index, blood pressure, and lipid areas under the curve were associated with accelerated vascular aging. Conclusions In young people with T1DM, persistent poor glycemic control and higher levels of traditional CVRF s are independently associated with arterial aging. Improving glycemic control and interventions to lower CVRF s may prevent future cardiovascular events in young individuals with T1DM.

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.

Aortic Pulsatility Propagates Intracranially and Correlates with Dilated Perivascular Spaces and Small Vessel Compliance

INTRODUCTION

To test the hypotheses that changes in the aortic pulse-wave produced by arterial stiffening are (1) propagated into cerebral small vessels, (2) associated with reduced compliance of small cerebral arterial vessels, and (3) associated with the presence of dilated perivascular spaces (PVS).

METHODS

Fifteen volunteers and 19 patients with late-onset depression (LOD) were prospectively recruited, of which 6 fulfilled the criteria for treatment-resistant depression (TRD). Aortic pulse-wave velocity (PWV) was determined using Carotid-Femoral Doppler. Pulse-wave analysis (PWA) was performed using a SphygmoCor system. White-matter lesion load and PVS were scored on established MRI scales. Cerebral arterial and aqueductal cerebrospinal fluid (CSF) flow patterns were studied using quantitative phase-contrast angiography.

RESULTS

Depressed patients had more PVS (P < .05) and prolongation of the width of the arterial systolic pulse-wave in the carotid arteries (P < .01). There was no significant group difference for any PWV or PWA measurement. TRD patients showed more PVS than other LOD patients (P < .05). The fractional width of the arterial systolic peak correlated significantly with augmentation index (AIx) and heart rate-corrected augmentation index (AIx75; R² = 0.302, P < .01and R² = 0.363, P < .01 respectively). Arterial-aqueductal delay showed a negative correlation with estimated aortic systolic pressure (PWVsys; R² =  0.293; P < .01), AIx (R² = -0.491; P < .01) and AIx75 (R² = -0.310; P < .01). PVS scores correlated with AIx (R² = 0.485; P < .01) and AIx75 (R² = -0.292; P < .01).

CONCLUSION

Our findings support the hypothesis that increased arterial pulsatility resulting from central arterial stiffness propagates directly into cerebral vessels and is associated with the development of microvascular angiopathy, characterized by dilated PVS and decreased compliance of small arterial vessels.

Reducing lung liquid volume increases biventricular outputs and systemic arterial blood flows despite decreased cardiac filling pressures in fetal lambs

As prior work has shown that reducing lung liquid volume 1) increases pulmonary arterial (PA) blood flow, 2) augments right ventricular (RV) output/power, and 3) decreases left atrial (LA) pressure, we tested the hypothesis that this perturbation has global cardiovascular effects. Ten anesthetized, open-chest fetal lambs (128 ± 2 days gestation, full term = 147 days) were acutely instrumented with 1) LA and right atrial (RA) catheters, 2) aortic and pulmonary trunk catheters, 3) brachiocephalic trunk, aortic isthmus, ductal, and left PA flow probes to obtain left ventricular (LV) and RV outputs and hydraulic power and flow in the descending thoracic aorta, and 4) an endotracheal tube to remove lung liquid. A 17 ± 7 ml/kg reduction of lung liquid volume 1) decreased LA and RA pressures similarly (1.5-1.6 mmHg, P < 0.001), 2) augmented LV and RV outputs (21-24%, P < 0.001) and total power (27-28%, P < 0.005), 3) increased systolic flows in the brachiocephalic trunk (18%, P < 0.001), aortic isthmus (29%, P < 0.005), ductus (12%, P < 0.005), and descending thoracic aorta (16%, P < 0.001), 4) increased mean PA flow via a higher systolic inflow (37%, P < 0.001) and lower diastolic backflow (-16%, P < 0.05), and 5) did not change systemic vascular conductance or arterial compliance but increased both pulmonary vascular conductance and arterial compliance (1.8-fold, P < 0.001). These data suggest that hemodynamic effects of lung liquid volume reduction are not confined to the lungs but extend to all cardiac chambers via rises in LV and RV outputs and power, despite falls in cardiac filling pressures, as well as the systemic circulation, via downstream increases in systolic flows of major central arteries.

Hypertension and transcatheter aortic valve replacement: parallel or series?

Aortic stenosis (AS) is the most common valvular heart disease in the elderly and it causes significant morbidity and mortality. Hypertension is also highly prevalent in elderly patients with AS, and AS patients with hypertension have worse outcomes. Accurate assessment of AS severity and understanding its relationship with arterial compliance has become increasingly important as the options for valve management, particularly transcatheter interventions, have grown. The parameters used for quantifying stenosis severity have traditionally mainly focused on the valve itself. However, AS is now recognized as a systemic disease involving aging ventricles and stiff arteries rather than one limited solely to the valve. Over the last decade, valvuloarterial impedance, a measure of global ventricular load, has contributed to our understanding of the pathophysiology and course of AS in heterogeneous patients, even when segregated by symptoms and severity. This review summarizes our growing understanding of the interplay between ventricle, valve, and vessel, with a particular emphasis on downstream vascular changes after transcatheter aortic valve replacement and the role of valvuloarterial impedance in predicting left ventricular changes and prognosis in patients with various transvalvular flow patterns.

Arterial stiffness and subclinical aortic damage of reclassified subjects as stage 1 hypertension according to the new 2017 ACC/AHA blood pressure guidelines

Background: The 2017 ACC/AHA blood pressure (BP) guidelines generated controversies due to the new proposed BP cut-off values defining hypertension. We aimed to assess aortic stiffness of subjects who are reclassified as stage 1 hypertensive according to the new guidelines and compare them with the subjects of "elevated BP" category. Patients and methods. Data from the "Corinthia" study, an observational, cross-sectional survey of 2,043 participants were analyzed. Subjects were classified into 4 groups: group A: systolic pressure (SBP) 120-129 and diastolic pressure (DBP) < 80 mmHg, group B: SBP 130-139 or DBP 80-89 mmHg, group B1: SBP 130-139 and DBP < 80 mmHg and group B2: SBP 130-139 and DBP 80-89 mmHg. Aortic stiffness was assessed by carotid-to-femoral pulse wave velocity (PWV). A value of PWV > 10m/s was consider indicative of asymptomatic organ damage while values of PWV exceeded the 90 % percentile for each age group were consider as abnormal. Results: Groups B, B1 and B2 have significantly increased PWV compared to group A, independently from age and other risk factors (PWV: 9.2 ± 2.8 vs 9.4 ± 2.7 vs 8.6 ± 2.5 vs 8.1 ± 2.3 m/s, p < 0.01, respectively). The prevalence of PWV > 10 m/s and abnormal PWV values in group A was significantly lower than the corresponding prevalence in randomly selected, age-matched subjects from group B (13.5 % vs 24.4 %, p = 0.027 and 5.6 % vs 14.2 %, p = 0.022, respectively). Conclusions: The reclassified subjects as stage 1 hypertensive by the new guidelines have a significantly increased aortic stiffness and greater prevalence in asymptomatic aortic damage compared to subjects with elevated BP. This finding may indirectly explain the increased cardiovascular risk of this group.

Habitual physical activity and central artery stiffening in older adults: the Atherosclerosis Risk in Communities study

INTRODUCTION

Regular physical activity appears to attenuate or even reverse age-related arterial stiffening. Yet, it is not clear if the reduced stiffening associated with habitual physical activity is also observed in community-dwelling older adults.

METHODS

Among 3893 older adults in a prospective cohort study, we associated physical activity with measures of central arterial stiffness (via carotid-femoral pulse wave velocity or cfPWV) and pressure pulsatility (via central pulse pressure or cPP). We also examined the association of long-term habitual physical activity, measured as persistence in physical activity levels from mid-life to late-life, with cfPWV and cPP among 1747 participants.

RESULTS

The adjusted mean difference in cfPWV was lower, reflecting less arterial stiffness, for those with moderate (ß = -0.30 m/s) or high (ß = -0.38 m/s) physical activity compared with no physical activity. The adjusted mean difference in cPP was also lower for those with high (ß = -2.49 mmHg) physical activity, relative to no physical activity. Stronger effect estimates were observed among those with persistent physical activity from mid-life to late-life.

CONCLUSION

Higher physical activity in late-life, and habitual physical activity from mid-life to late-life, is associated with lower central arterial stiffness and pressure pulsatility in a large population-based sample of community-dwelling older adults.

Disconnection of pulmonary and systemic arterial stiffness in COPD

Background

Both pulmonary arterial stiffening and systemic arterial stiffening have been described in COPD. The aim of the current study was to assess pulse wave velocity (PWV) within these two arterial beds to determine whether they are separate or linked processes.

Materials and methods

In total, 58 participants with COPD and 21 healthy volunteers (HVs) underwent cardiac magnetic resonance imaging (MRI) and were tested with a panel of relevant biomarkers. Cardiac MRI was used to quantify ventricular mass, volumes, and pulmonary (pulse wave velocity [pPWV] and systemic pulse wave velocity [sPWV]).

Results

Those with COPD had higher pPWV (COPD: 2.62 vs HV: 1.78 ms⁻¹, p=0.006), higher right ventricular mass/volume ratio (RVMVR; COPD: 0.29 vs HV: 0.25 g/mL, p=0.012), higher left ventricular mass/volume ratio (LVMVR; COPD: 0.78 vs HV: 0.70 g/mL, p=0.009), and a trend toward a higher sPWV (COPD: 8.7 vs HV: 7.4 ms⁻¹, p=0.06). Multiple biomarkers were elevated: interleukin-6 (COPD: 1.38 vs HV: 0.58 pg/mL, p=0.02), high-sensitivity C-reactive protein (COPD: 6.42 vs HV: 2.49 mg/L, p=0.002), surfactant protein D (COPD: 16.9 vs HV: 9.13 ng/mL, p=0.001), N-terminal pro-brain natriuretic peptide (COPD: 603 vs HV: 198 pg/mL, p=0.001), and high-sensitivity troponin I (COPD: 2.27 vs HV: 0.92 pg/mL, p<0.001). There was a significant relationship between sPWV and LVMVR (p=0.01) but not pPWV (p=0.97) nor between pPWV and RVMVR (p=0.27).

Conclusion

Pulmonary arterial stiffening and systemic arterial stiffening appear to be disconnected and should therefore be considered independent processes in COPD. Further work is warranted to determine whether both these cause an increased morbidity and mortality and whether both can be targeted by similar pharmacological therapy or whether different strategies are required for each.

The role of increased glucose on neurovascular dysfunction in patients with the metabolic syndrome

Metabolic syndrome (MetS) causes autonomic alteration and vascular dysfunction. The authors investigated whether impaired fasting glucose (IFG) is the main cause of vascular dysfunction via elevated sympathetic tone in nondiabetic patients with MetS. Pulse wave velocity, muscle sympathetic nerve activity (MSNA), and forearm vascular resistance was measured in patients with MetS divided according to fasting glucose levels: (1) MetS+IFG (blood glucose ≥100 mg/dL) and (2) MetS-IFG (<100 mg/dL) compared with healthy controls. Patients with MetS+IFG had higher pulse wave velocity than patients with MetS-IFG and controls (median 8.0 [interquartile range, 7.2-8.6], 7.3 [interquartile range, 6.9-7.9], and 6.9 [interquartile range, 6.6-7.2] m/s, P=.001). Patients with MetS+IFG had higher MSNA than patients with MetS-IFG and controls, and patients with MetS-IFG had higher MSNA than controls (31±1, 26±1, and 19±1 bursts per minute; P<.001). Patients with MetS+IFG were similar to patients with MetS-IFG but had higher forearm vascular resistance than controls (P=.008). IFG was the only predictor variable of MSNA. MSNA was associated with pulse wave velocity (R=.39, P=.002) and forearm vascular resistance (R=.30, P=.034). In patients with MetS, increased plasma glucose levels leads to an adrenergic burden that can explain vascular dysfunction.

Impact of Vascular Hemodynamics on Aortic Stenosis Evaluation: New Insights Into the Pathophysiology of Normal Flow-Small Aortic Valve Area-Low Gradient Pattern

Background

About 50% of normal‐flow/low‐gradient patients (ie, low mean gradient [MG] or peak aortic jet velocity and small aortic valve area) have severe aortic valve calcification as measured by computed tomography. However, they are considered to have moderate aortic stenosis (AS) in current American College of Cardiology/American Heart Association guidelines. The objective was thus to evaluate the effect of hypertension and reduced arterial compliance (rAC) on MG and V_peak measurements.

Methods and Results

Doppler‐echocardiography was performed in 4 sheep with experimentally induced severe and critical AS at: (1) normal aortic pressure, (2) during hypertension, and (3) with rAC. Hypertension and rAC induced a substantial decrease in MG/V_peak compared with normal stage (both P≤0.03) despite a stable transvalvular flow (P>0.16). Hypertension and rAC resulted in a greater reduction of MG in critical (−42%) compared with severe (−35%) AS (P˂0.0001). Comprehensive Doppler‐echocardiography and computed tomography were performed in 220 AS patients (mean age: 69±13 years; MG 29±18 mm Hg) with normal flow. The population was divided in 3 groups according to the presence of hypertension and rAC. The slope of the linear association between MG/V_peak and aortic valve calcification divided by the cross‐sectional area of the aortic annulus was significantly reduced in patients with hypertension and/or rAC compared with normotensive/normal AC patients (P<0.01). Accordingly, patients with normal‐flow/low‐gradient and severe aortic valve calcification density were more frequent in hypertension and rAC groups compared with the normotensive/normal‐AC group (16% and 12% compared with 2%; P=0.03).

Conclusions

Hypertension and rAC are associated with a substantial reduction in MG/V_peak for similar aortic valve calcification (ie, similar AS anatomic severity), which may lead to underestimation of AS hemodynamic severity.

Arteriosclerosis in the ventral aorta and epicarditis in the bulbus arteriosus of Atlantic salmon (Salmo salar L)

Spontaneous mortality of seemingly healthy, farmed Atlantic salmon (Salmo salar L) is an increasing problem in Norwegian aquaculture. In this study, we present a morphological study of the previously undescribed syndrome of arteriosclerosis of the ventral aorta and epicarditis of the adjacent bulbus arteriosus found in farmed Atlantic salmon, with wild-captured fish as a control group. Both the ventral aorta and epicardium are vital for correct arterial compliance and vascular resistance in the respiratory capillaries of the gills. We discuss the possible implications of ventral aorta arteriosclerosis and epicarditis for blood vascular health and in particular for the increasing frequency of spontaneous gill bleeding in farmed salmon. As both these conditions primarily occur in farmed salmon, we suggest that they should be considered pathological.

Interrelationships Among Various Measures of Central Artery Stiffness

BACKGROUND

A number of different techniques and methodologies have been applied to quantify stiffness of arteries. Because measures of arterial stiffness differ in regards to measurement locations as well as properties, it is not clear how well these measures that are supposed to reflect the same arterial wall properties are related.

METHODS

Interrelationships between different measures of arterial stiffness were evaluated in 50 apparently healthy subjects varying in age.

RESULTS

Significant relations ranging from mild to strong were observed among measures of arterial stiffness while some measures were not significantly associated. Cardio-ankle vascular index (CAVI) was significantly associated with carotid-femoral pulse wave velocity (cfPWV) and brachial-ankle pulse wave velocity (baPWV). Ultrasound-derived measures of arterial stiffness (e.g., compliance, distensibility) were weakly or not significantly related to pulse wave velocity (PWV) measures. The limits of agreement between each of arterial stiffness measures based on the Bland-Altman analyses indicate that there were close agreements (CI = 1.12-1.52) between CAVI, cfPWV, and baPWV. However, agreements between PWV measures and ultrasound-derived measures were mild to moderate. β-stiffness index demonstrated large 95% CIs with other measures. When associations between relative changes in various measures of arterial stiffness in response to isometric handgrip exercise were evaluated, the general trend of associations was similar to the relations observed at rest. β-stiffness index was not related to most measures of arterial stiffness.

CONCLUSION

These results suggest that the techniques used to assess arterial stiffness may not be interchangeable in clinical and research settings and that comparisons of findings obtained with different arterial stiffness measures should be conducted with caution.

Comparison of High-Protein, Intermittent Fasting Low-Calorie Diet and Heart Healthy Diet for Vascular Health of the Obese

AIM

It has been debated whether different diets are more or less effective in long-term weight loss success and cardiovascular disease prevention among men and women. To further explore these questions, the present study evaluated the combined effects of a high-protein, intermittent fasting, low-calorie diet plan compared with a heart healthy diet plan during weight loss, and weight loss maintenance on blood lipids and vascular compliance of obese individuals.

METHODS

The experiment involved 40 obese adults (men, n = 21; women, n = 19) and was divided into two phases: (a) 12-week high-protein, intermittent fasting, low-calorie weight loss diet comparing men and women (Phase 1) and (b) a 1-year weight maintenance phase comparing high-protein, intermittent fasting with a heart healthy diet (Phase 2). Body weight, body mass index (BMI), blood lipids, and arterial compliance outcomes were assessed at weeks 1 (baseline control), 12 (weight loss), and 64 (12 + 52 week; weight loss maintenance).

RESULTS

At the end of weight loss intervention, concomitant reductions in body weight, BMI and blood lipids were observed, as well as enhanced arterial compliance. No sex-specific differences in responses were observed. During phase 2, the high-protein, intermittent fasting group demonstrated a trend for less regain in BMI, low-density lipoprotein (LDL), and aortic pulse wave velocity than the heart healthy group.

CONCLUSION

Our results suggest that a high-protein, intermittent fasting and low-calorie diet is associated with similar reductions in BMI and blood lipids in obese men and women. This diet also demonstrated an advantage in minimizing weight regain as well as enhancing arterial compliance as compared to a heart healthy diet after 1 year.

Antihypertensive treatment decreases arterial stiffness at night but not during the day. Results from the Hypertension in the Very Elderly Trial

The main Hypertension in the Very Elderly Trial (HYVET) demonstrated a very marked reduction in cardiovascular events by treating hypertensive participants 80 years or older with a low dose, sustained release prescription of indapamide (indapamide SR, 1.5 mg) to which was added a low dose of an angiotensin converting enzyme inhibitor in two-thirds of cases (perindopril 2-4 mg). This report from the ambulatory blood pressure sub-study investigates whether changes in arterial stiffness and ambulatory blood pressure (BP) could both explain the benefits observed in the main trial. A total of 139 participants were randomized to placebo [67] and to active treatment [72] and had both day and night observations of BP and arterial stiffness as determined from the Q wave Korotkoff diastolic (QKD) interval. The QKD interval was 5.6 ms longer (p = 0.017) in the actively treated group at night than in the placebo group. This was not true for the more numerous daytime readings so that 24-h results were similar in the two groups. The QKD interval remained longer at night in the actively treated group even when adjusted for systolic pressure, heart rate and height. The reduced arterial stiffness at night may partly explain the marked benefits observed in the main trial.

A guide to uncertainty quantification and sensitivity analysis for cardiovascular applications

As we shift from population-based medicine towards a more precise patient-specific regime guided by predictions of verified and well-established cardiovascular models, an urgent question arises: how sensitive are the model predictions to errors and uncertainties in the model inputs? To make our models suitable for clinical decision-making, precise knowledge of prediction reliability is of paramount importance. Efficient and practical methods for uncertainty quantification (UQ) and sensitivity analysis (SA) are therefore essential. In this work, we explain the concepts of global UQ and global, variance-based SA along with two often-used methods that are applicable to any model without requiring model implementation changes: Monte Carlo (MC) and polynomial chaos (PC). Furthermore, we propose a guide for UQ and SA according to a six-step procedure and demonstrate it for two clinically relevant cardiovascular models: model-based estimation of the fractional flow reserve (FFR) and model-based estimation of the total arterial compliance (CT ). Both MC and PC produce identical results and may be used interchangeably to identify most significant model inputs with respect to uncertainty in model predictions of FFR and CT . However, PC is more cost-efficient as it requires an order of magnitude fewer model evaluations than MC. Additionally, we demonstrate that targeted reduction of uncertainty in the most significant model inputs reduces the uncertainty in the model predictions efficiently. In conclusion, this article offers a practical guide to UQ and SA to help move the clinical application of mathematical models forward. Copyright © 2015 John Wiley & Sons, Ltd.

Arterial stiffness of lifelong Japanese female pearl divers

Japanese female pearl divers called Ama specialize in free diving in the cold sea for collecting foods and pearls in oysters. Exercising in the water combined with marked bradycardia and pressor responses provides a circulatory challenge to properly buffer or cushion elevated cardiac pulsations. Because Ama perform repeated free dives throughout their lives, it is possible that they may have adapted similar arterial structure and function to those seen in diving mammals. We compared arterial stiffness of lifelong Japanese pearl divers with age-matched physically inactive adults living in the same fishing villages. A total of 115 Japanese female pearl divers were studied. Additionally, 50 physically inactive adults as well as 33 physically active adults (participating in community fitness programs) living in the same coastal villages were also studied. There were no differences in age (∼65 yr), body mass index, and brachial blood pressure between the groups. Measures of arterial stiffness, cardio-ankle vascular index and β-stiffness index were lower (P < 0.05) in pearl divers and physically active adults than in their physically inactive peers. Augmentation pressure and augmentation index adjusted for the heart rate of 75 beats/min were lower (P < 0.05) in pearl divers than in other groups. These results indicate that lifelong Japanese pearl divers demonstrate reduced arterial stiffness and arterial wave reflection compared with age-matched physically inactive peers living in the same fishing villages.

The acute effect of maximal exercise on central and peripheral arterial stiffness indices and hemodynamics in children and adults

This study compared the effects of a bout of maximal running exercise on arterial stiffness in children and adults. Right carotid blood pressure and artery stiffness indices measured by pulse wave velocity (PWV), compliance and distensibility coefficients, stiffness index α and β (echo-tracking), contralateral carotid blood pressure, and upper and lower limb and central/aortic PWV (applanation tonometry) were taken at rest and 10 min after a bout of maximal treadmill running in 34 children (7.38 ± 0.38 years) and 45 young adults (25.22 ± 0.91 years) having similar aerobic potential. Two-by-two repeated measures analysis of variance and analysis of covariance were used to detect differences with exercise between groups. Carotid pulse pressure (PP; η(2) = 0.394) increased more in adults after exercise (p < 0.05). Compliance (η(2) = 0.385) decreased in particular in adults and in those with high changes in distending pressure, similarly to stiffness index α and β. Carotid PWV increased more in adults and was related to local changes in PP but not mean arterial pressure (MAP). Stiffness in the lower limbs decreased (η(2) = 0.115) but apparently only in those with small MAP changes (η(2) = 0.111). No significant exercise or group interaction effects were found when variables were adjusted to height. An acute bout of maximal exercise can alter arterial stiffness and hemodynamics in the carotid artery and within the active muscle beds. Arterial stiffness and hemodynamic response to metabolic demands during exercise in children simply reflect their smaller body size and may not indicate a particular physiological difference compared with adults.

Elastic and Muscular Arteries Differ in Structure, Basal NO Production and Voltage-Gated Ca(2+)-Channels

In the last decades, the search for mechanisms underlying progressive arterial stiffening and for interventions to avoid or reverse this process has gained much attention. In general, arterial stiffening displays regional variation and is, for example, during aging more prominent in elastic than in muscular arteries. We hypothesize that besides passive also active regulators of arterial compliance [i.e., endothelial and vascular smooth muscle cell (VSMC) function] differ between these arteries. Hence, it is conceivable that these vessel types will display different time frames of stiffening. To investigate this hypothesis segments of muscular arteries such as femoral and mesenteric arteries and elastic arteries such as the aorta and carotid artery were isolated from female C57Bl6 mice (5–6 months of age, n = 8). Both microscopy and passive stretching of the segments in a myograph confirmed that passive mechanical properties (elastin, collagen) of elastic and muscular arteries were significantly different. Endothelial function, more specifically basal nitric oxide (NO) efficacy, and VSMC function, more specifically L-type voltage-gated Ca²⁺ channel (VGCC)-mediated contractions, were determined by α₁-adrenoceptor stimulation with phenylephrine (PE) and by gradual depolarization with elevated extracellular K⁺ in the absence and presence of eNOS inhibition with L-NAME. PE-mediated isometric contractions significantly increased after inhibition of NO release with L-NAME in elastic, but not in muscular vessel segments. This high basal eNOS activity in elastic vessels was also responsible for shifts of K⁺ concentration-contraction curves to higher external K⁺. VGCC-mediated contractions were similarly affected by depolarization with elevated K⁺ in muscular artery segments or in elastic artery segments in the absence of basal NO. However, K⁺-induced contractions were inhibited by the VGCC blocker diltiazem with significantly higher sensitivity in the muscular arteries, suggestive of different populations of VGCC isoforms in both vessel types. The results from the present study demonstrate that, besides passive arterial wall components, also active functional components contribute to the heterogeneity of arterial compliance along the vascular tree. This crucially facilitates the search for (patho) physiological mechanisms and potential therapeutic targets to treat or reverse large artery stiffening as occurring in aging-induced arterial stiffening.

Left Ventricle-Arterial System Interaction in Heart Failure

Ejection fraction (EF) has been viewed as an important index in assessing the contractile state of the left ventricle (LV). However, it is frequently inadequate for the diagnosis and management of heart failure (HF), as a significant subset of HF patients have been found to have reduced EF (HFrEF) whereas others have preserved EF (HFpEF). It should be noted that the function of the LV is dependent on both preload and afterload, as well as its intrinsic contractile state. Furthermore, stroke volume (SV) is dependent on the properties of the arterial system (AS). Thus, the LV-arterial system interaction plays an important role in those patients with HF. This aspect is investigated through the analysis of the specific parameters involved in the coupling of the LV and AS. This includes contractility and the systolic/diastolic indices of the LV. Furthermore, AS afterload parameters such as vascular stiffness and arterial compliance, and their derived coupling coefficient, are also investigated. We conclude that those parameters, which relate to LV structural changes, are most appropriate in quantifying the LV-AS interaction.