Augmentation pressure is influenced by ventricular contractility/relaxation dynamics: novel mechanism of reduction of pulse pressure by nitrates

The effects of empagliflozin on systemic haemodynamic function: three randomized, placebo-controlled trials

BACKGROUND

Sodium glucose cotransporter 2 inhibitors lower blood pressure. The underlying mechanisms are multifactorial and include effects on vascular function. We examined the systemic hemodynamic effects of empagliflozin in patients with type 2 diabetes mellitus (DM2) with and without chronic kidney disease (CKD) and in patients with nondiabetic CKD.

METHODS

Three double-blinded, randomized, placebo-controlled cross-over trials, including patients with DM2 and preserved renal function (n = 16), DM2 and CKD (n = 17) and nondiabetic CKD (n = 16). Participants were randomized to 4 weeks of empagliflozin 10 mg or placebo and crossed over after a 2-week washout. We measured brachial and central 24-h ambulatory blood pressure (ABP), pulse wave velocity (PWV), augmentation index (AIx@75), markers of nitric oxide and erythrocyte sodium sensitivity (ESS), a marker of endothelial glycocalyx function.

RESULTS

Empagliflozin reduced PWV [-0.16 m/s, 95% confidence interval (95% CI): -0.26; -0.06, P = 0.002], AIx@75 (-2.17%, 95% CI: -3.31; -1.02, P < 0.001) and brachial and central ABP in the combined study population (n = 49). Changes in PWV and AIx@75 correlated to changes in systolic brachial ABP. Markers of nitric oxide did not increase, but empagliflozin decreased ESS, which was correlated to an increase in haematocrit.

CONCLUSION

Empagliflozin decreased arterial stiffness, mediated partly by a decrease in brachial ABP. We found no increase in nitric oxide activity, but ESS decreased. While this may be explained partly by a change in haematocrit, it could indicate an improvement in endothelial glycocalyx function.

TRIAL REGISTRATION

EU Clinical Trials Register 2019-004303-12, 2019-004447-80 and 2019-004467-50.

Body composition affects blood lipids and vascular function in metabolically unhealthy or metabolically healthy older adult women with obesity: A multi-group path analysis/impact verification following latent profile analysis

OBJECTIVES

This study aimed to perform latent profile analysis (LPA) in older adult women with metabolic syndrome to extract a group according to their characteristics while controlling for body composition, blood lipid levels, and vascular function. The study also examined the relationship between different variables.

METHODS

The participants were 35 women aged ≥65 years, who met the Korean female standards for metabolic syndrome. Blood collection, blood pressure measurements, and vascular function measurements were performed. LPA and multigroup path analysis (MGPA) were performed to statistically analyze the effects of body composition on blood lipid levels and vascular function in older adult women with metabolic syndrome. Mplus 8.3 and jamovi 2.0.0 were used for the analyses, and the control significance level was set at .05.

RESULTS

The participants were divided into the following three groups: (G1) metabolically unhealthy participants with normal weight, (G2) normal-weight participants with arteriosclerosis, and (G3) obese but metabolically healthy participants (G3). The effect of body composition on blood lipid levels showed a significant difference only in G1. The effect of body composition on vascular function was influenced by various variables in G1 and G3, while G1 showed a higher explanatory power.

CONCLUSIONS

The MGPA results showed that the relationship between variables differs depending on the group. Therefore, the metabolic syndrome should be studied by subdividing it and confirming the characteristics of the classified groups, such as normal-weight but metabolically unhealthy individuals and obese but metabolically healthy individuals.

Central and Peripheral Hemodynamics in Young Adults Who Use Water Pipes and the Acute Effects of Water-Pipe Use

BACKGROUND

Tobacco use via water pipe (commonly referred to as water-pipe smoking [WPS]) is popular among young adults globally and exposes those who smoke to toxicants.

RESEARCH QUESTION

Is WPS associated with impaired measures of arterial function and does WPS acutely impair these measures in young adults?

STUDY DESIGN AND METHODS

We assessed heart rate (HR), brachial and aortic BP, HR-adjusted augmentation index (AI), and carotid-femoral pulse wave velocity (CFPWV) in 62 individuals who use water pipes and 34 individuals who have never used a water pipe recruited from the community (mean age, 22.5 ± 3.0 years; 48% female). Measurements were obtained before and after an outdoor session of WPS among participants who use water pipes and among the control group of participants who have never used a water pipe. Measurements were compared after vs before exposure and between those who use and those who do not use water pipes, adjusting for possible confounders using linear regression.

RESULTS

Participants who use water pipes and control participants had similar demographic characteristics. BP and HR increased acutely after WPS (brachial systolic BP by 4.13 mm Hg [95% CI, 1.91-6.36 mm Hg]; aortic systolic BP by 2.31 mm Hg [95% CI, 0.28-4.33 mm Hg]; brachial diastolic BP by 3.69 mm Hg [95% CI, 1.62-5.77 mm Hg]; aortic diastolic BP by 3.03 mm Hg [95% CI, 0.74-5.33 mm Hg]; and HR by 7.75 beats/min [95% CI, 5.46-10.04 beats/min]), but not in the control group. AI was significantly higher in participants who use water pipes compared with those who do not (9.02% vs 3.06%; P = .03), including after adjusting for BMI and family history of cardiovascular disease (β = 6.12; 95% CI, 0.55-11.69; P = .03) and when assessing habitual tobacco use via water-pipe extent (water pipes used/day × water-pipe use duration) in water-pipe-years (β = 2.51/water-pipe-year; 95% CI, 0.10-4.92/water-pipe-year; P = .04). However, CFPWV was similar in those who use water pipes and those who do not, and AI and CFPWV did not change acutely after WPS.

INTERPRETATION

In apparently healthy young individuals from the community, habitual WPS was associated with increased AI, a predictor of cardiovascular risk, and one WPS session acutely increased HR and brachial and aortic BP.

Effect of acute handgrip and aerobic exercise on wasted pressure effort and arterial wave reflections in healthy aging

Aging increases arterial stiffness and wave reflections that augment left ventricular wasted pressure effort (WPE). A single bout of exercise may be effective at acutely reducing WPE via reductions in arterial wave reflections. In young adults (YA) acute aerobic exercise decreases, whereas handgrip increases, wave reflections. Whether acute exercise mitigates or exacerbates WPE and arterial wave reflection in healthy aging warrants further examination. The purpose of this study was to determine if there are age-related differences in WPE and wave reflection during acute handgrip and aerobic exercise. When compared with baseline, WPE increased substantially in older adults (OA) during handgrip (5,219 ± 2,396 vs. 7,019 ± 2,888 mmHg·ms, P < 0.001). When compared with baseline, there was a robust reduction in WPE in OA during moderate-intensity aerobic exercise (5,428 ± 2,084 vs. 3,290 ± 1,537 mmHg·ms, P < 0.001), despite absolute WPE remaining higher in OA compared with YA during moderate-intensity aerobic exercise (OA 3,290 ± 1,537 vs. YA 1,188 ± 962 mmHg·ms, P < 0.001). There was no change in wave reflection timing indexed to ejection duration in OA during handgrip (40 ± 6 vs. 38 ± 4%, P = 0.41) or moderate-intensity aerobic exercise (40 ± 5 vs. 42 ± 8%, P = 0.99). Conversely, there was an earlier return of wave reflection in YA during handgrip (60 ± 11 vs. 52 ± 6%, P < 0.001) and moderate-intensity aerobic exercise (59 ± 7 vs. 51 ± 9%, P < 0.001). Changes in stroke volume were not different between groups during handgrip (P = 0.08) or aerobic exercise (P = 0.47). The greater increase in WPE during handgrip and decrease in WPE during aerobic exercise suggest that aortic hemodynamic responses to acute exercise are exaggerated with healthy aging without affecting stroke volume.NEW & NOTEWORTHY We demonstrated that acute aerobic exercise attenuated, whereas handgrip augmented, left ventricular hemodynamic load from wave reflections more in healthy older (OA) compared with young adults (YA) without altering stroke volume. These findings suggest an exaggerated aortic hemodynamic response to acute exercise perturbations with aging. They also highlight the importance of considering exercise modality when examining aortic hemodynamic responses to acute exercise in older adults.

Cardiac contractility is a key factor in determining pulse pressure and its peripheral amplification

Background

Arterial stiffening and peripheral wave reflections have been considered the major determinants of raised pulse pressure (PP) and isolated systolic hypertension, but the importance of cardiac contractility and ventricular ejection dynamics is also recognised.

Methods

We examined the contributions of arterial compliance and ventricular contractility to variations in aortic flow and increased central (cPP) and peripheral (pPP) pulse pressure, and PP amplification (PPa) in normotensive subjects during pharmacological modulation of physiology, in hypertensive subjects, and in silico using a cardiovascular model accounting for ventricular-aortic coupling. Reflections at the aortic root and from downstream vessels were quantified using emission and reflection coefficients, respectively.

Results

cPP was strongly associated with contractility and compliance, whereas pPP and PPa were strongly associated with contractility. Increased contractility by inotropic stimulation increased peak aortic flow (323.9 ± 52.8 vs. 389.1 ± 65.1 ml/s), and the rate of increase (3193.6 ± 793.0 vs. 4848.3 ± 450.4 ml/s2) in aortic flow, leading to larger cPP (36.1 ± 8.8 vs. 59.0 ± 10.8 mmHg), pPP (56.9 ± 13.1 vs. 93.0 ± 17.0 mmHg) and PPa (20.8 ± 4.8 vs. 34.0 ± 7.3 mmHg). Increased compliance by vasodilation decreased cPP (62.2 ± 20.2 vs. 45.2 ± 17.8 mmHg) without altering d P / d t , pPP or PPa. The emission coefficient changed with increasing cPP, but the reflection coefficient did not. These results agreed with in silico data obtained by independently changing contractility/compliance over the range observed in vivo.

Conclusions

Ventricular contractility plays a key role in raising and amplifying PP, by altering aortic flow wave morphology.

Prognostic value of central blood pressure on the outcomes of embolic stroke of undetermined source

We investigated the prognostic impact of central blood pressure (BP) on outcomes in patients with embolic stroke of undetermined source (ESUS). The prognostic value of central BP according to ESUS subtype was also evaluated. We recruited patients with ESUS and data on their central BP parameters (central systolic BP [SBP], central diastolic BP [DBP], central pulse pressure [PP], augmentation pressure [AP], and augmentation index [AIx]) during admission. ESUS subtype classification was arteriogenic embolism, minor cardioembolism, two or more causes, and no cause. Major adverse cardiovascular event (MACE) was defined as recurrent stroke, acute coronary syndrome, hospitalization for heart failure, or death. Over a median of 45.8 months, 746 patients with ESUS were enrolled and followed up. Patients had a mean age of 62.8 years, and 62.2% were male. Multivariable Cox regression analysis showed that central SBP and PP were associated with MACE. All-cause mortality was independently associated with AIx. In patients with no cause ESUS, central SBP and PP, AP, and AIx were independently associated with MACE. AP and AIx were independently associated with all-cause mortality (all p < 0.05). We demonstrated that central BP can predict poor long-term prognosis in patients with ESUS, especially those with the no cause ESUS subtype.

Impaired β 2 -adrenergic endothelium-dependent vasodilation in patients previously hospitalized with coronavirus disease 2019

AIM

The pulse wave response to salbutamol (PWRS) - change in augmentation index (AIx) - provides a means to assess endothelial vasodilator function in vivo . Endothelial dysfunction plays a relevant role in the pathogenesis of hypertension and cardiovascular disease and appears to underlie many of the complications of coronavirus disease 2019 (COVID-19). However, to what degree this persists after recovery is unknown.

METHODS

Individuals previously hospitalized with COVID-19, those recovered from mild symptoms and seronegative controls with well known risk factors for endothelial dysfunction were studied. To assess the involvement of nitric oxide-cyclic guanosine monophosphate pathway (NO-cGMP) on PWRS, sildenafil was also administrated in a subsample.

RESULTS

One hundred and one participants (60 men) aged 47.8 ± 14.1 (mean ± SD) years of whom 33 were previously hospitalized with COVID-19 were recruited. Salbutamol had minimal effect on haemodynamics including blood pressure and heart rate. It reduced AIx in controls ( n  = 34) and those recovered from mild symptoms of COVID-19 ( n  = 34) but produced an increase in AIx in those previously hospitalized: mean change [95% confidence interval] -2.85 [-5.52, -0.188] %, -2.32 [-5.17,0.54] %, and 3.03 [0.06, 6.00] % for controls, those recovered from mild symptoms and those previously hospitalized, respectively ( P  = 0.001). In a sub-sample ( n  = 22), sildenafil enhanced PWRS (change in AIx 0.05 [-2.15,2.24] vs. -3.96 [-7.01. -2.18], P  = 0.006) with no significant difference between hospitalized ( n  = 12) and nonhospitalized participants ( n  = 10).

CONCLUSIONS

In patients previously hospitalized with COVID-19, there is long-lasting impairment of endothelial function as measured by the salbutamol-induced stimulation of the NO-cGMP pathway that may contribute to cardiovascular complications.

A coupled atrioventricular-aortic setup for in-vitro hemodynamic study of the systemic circulation: Design, fabrication, and physiological relevancy

In-vitro models of the systemic circulation have gained a lot of interest for fundamental understanding of cardiovascular dynamics and for applied hemodynamic research. In this study, we introduce a physiologically accurate in-vitro hydraulic setup that models the hemodynamics of the coupled atrioventricular-aortic system. This unique experimental simulator has three major components: 1) an arterial system consisting of a human-scale artificial aorta along with the main branches, 2) an artificial left ventricle (LV) sac connected to a programmable piston-in-cylinder pump for simulating cardiac contraction and relaxation, and 3) an artificial left atrium (LA). The setup is designed in such a way that the basal LV is directly connected to the aortic root via an aortic valve, and to the LA via an artificial mitral valve. As a result, two-way hemodynamic couplings can be achieved for studying the effects that the LV, aorta, and LA have on each other. The collected pressure and flow measurements from this setup demonstrate a remarkable correspondence to clinical hemodynamics. We also investigate the physiological relevancies of isolated effects on cardiovascular hemodynamics of various major global parameters found in the circulatory system, including LV contractility, LV preload, heart rate, aortic compliance, and peripheral resistance. Subsequent control over such parameters ultimately captures physiological hemodynamic effects of LV systolic dysfunction, preload (cardiac) diseases, and afterload (arterial) diseases. The detailed design and fabrication of the proposed setup is also provided.

Association between the reflection magnitude and blood pressure in a multiethnic cohort: the Healthy Life in an Urban Setting study

AIMS

Reflection magnitude (RM), the ratio of the amplitudes of the backward and forward central arterial pressure waves, has been shown to predict cardiovascular events. However, the association with blood pressure (BP) and hypertension is unclear.

METHODS

We assessed RM in 10 195 individuals of Dutch, South-Asian Surinamese, African Surinamese, Ghanaian, Turkish and Moroccan origin aged between 18 and 70 years (54.2% female) participating in the Healthy Life in an Urban Setting study. To determine RM, central arterial pressure and flow were reconstructed from finger BP. Hypertension was defined based on office-BP and medication. Associations with BP, hypertension, and hypertensive organ damage were assessed using linear regression models with correction for relevant covariates.

RESULTS

Mean RM was 62.5% (standard deviation [SD] 8.0) in men and 63.8% (SD 8.1) in women. RM was lowest in Dutch and highest in South-Asian and African participants. RM increased linearly with 1.35 (95% confidence interval [CI] 1.23-1.46) for every 10 mmHg increase in systolic BP from 120 mmHg onwards, while the relation with diastolic BP was nonlinear. RM was 2.40 (95% CI 2.04-2.76) higher in hypertensive men and 3.82 (95% CI 3.46-4.19) higher in hypertensive women compared to normotensive men and women. In hypertensive men and women with ECG-based left ventricular hypertrophy or albuminuria RM was 1.64 (95% CI 1.09-2.20) and 0.94 (95% CI 0.37-1.52) higher compared to hypertensive participants without hypertensive organ damage.

CONCLUSION

RM is associated with BP, hypertension and hypertensive organ damage, and may in part explain disparities in hypertension associated cardiovascular risk.

Association between the reflection magnitude and blood pressure in a multiethnic cohort: the Healthy Life in an Urban Setting study

Aims:

Reflection magnitude (RM), the ratio of the amplitudes of the backward and forward central arterial pressure waves, has been shown to predict cardiovascular events. However, the association with blood pressure (BP) and hypertension is unclear.

Methods:

We assessed RM in 10 195 individuals of Dutch, South-Asian Surinamese, African Surinamese, Ghanaian, Turkish and Moroccan origin aged between 18 and 70 years (54.2% female) participating in the Healthy Life in an Urban Setting study. To determine RM, central arterial pressure and flow were reconstructed from finger BP. Hypertension was defined based on office-BP and medication. Associations with BP, hypertension, and hypertensive organ damage were assessed using linear regression models with correction for relevant covariates.

Results:

Mean RM was 62.5% (standard deviation [SD] 8.0) in men and 63.8% (SD 8.1) in women. RM was lowest in Dutch and highest in South-Asian and African participants. RM increased linearly with 1.35 (95% confidence interval [CI] 1.23–1.46) for every 10 mmHg increase in systolic BP from 120 mmHg onwards, while the relation with diastolic BP was nonlinear. RM was 2.40 (95% CI 2.04–2.76) higher in hypertensive men and 3.82 (95% CI 3.46–4.19) higher in hypertensive women compared to normotensive men and women. In hypertensive men and women with ECG-based left ventricular hypertrophy or albuminuria RM was 1.64 (95% CI 1.09–2.20) and 0.94 (95% CI 0.37–1.52) higher compared to hypertensive participants without hypertensive organ damage.

Conclusion:

RM is associated with BP, hypertension and hypertensive organ damage, and may in part explain disparities in hypertension associated cardiovascular risk.

Increased Excess Pressure After Creation of an Arteriovenous Fistula in End-Stage Renal Disease

BACKGROUND

Reservoir-wave analysis (RWA) separates the arterial waveform into reservoir and excess pressure (XSP) components, where XSP is analogous to flow and related to left ventricular workload. RWA provides more detailed information about the arterial tree than traditional blood pressure (BP) parameters. In end-stage renal disease (ESRD), we have previously shown that XSP is associated with increased mortality and is higher in patients with arteriovenous fistula (AVF). In this study, we examined whether XSP increases after creation of an AVF in ESRD.

METHODS

Before and after a mean of 3.9 ± 1.2 months following creation of AVF, carotid pressure waves were recorded using arterial tonometry. XSP and its integral (XSPI) were derived using RWA through pressure wave analysis alone. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (CF-PWV).

RESURLTS

In 38 patients (63% male, age 59 ± 15 years), after AVF creation, brachial diastolic BP decreased (79 ± 10 vs. 72 ± 12 mm Hg, P = 0.002), but the reduction in systolic BP, was not statistically significant (133 ± 20 vs. 127 ± 26 mm Hg, P = 0.137). However, carotid XSP (14 [12-19] to 17 [12-22] mm Hg, P = 0.031) and XSPI increased significantly (275 [212-335] to 334 [241-439] kPa∙s, P = 0.015), despite a reduction in CF-PWV (13 ± 3.6 vs. 12 ± 3.5 m/s, P = 0.025).

CONCLUSIONS

Creation of an AVF resulted in increased XSP in this population, despite improvement in diastolic BP and aortic stiffness. These findings underline the complex hemodynamic impact of AVF on the cardiovascular system.

Arterial Stiffness and Cardiorespiratory Fitness Are Associated With Cognitive Function in Older Adults

Age-related cognitive impairment has been associated with arterial stiffening and decreased cardiorespiratory fitness. The aims of this cross-sectional study were to compare cognitive function domains and cardiovascular parameters in older adults (≥ 65 years old) with high and normal aortic stiffness (via carotid-femoral pulse wave velocity, cfPWV) and to explore relationships among cfPWV, carotid intima-media thickness, cardiorespiratory fitness, and cognitive function. Vascular and cognitive function were measured in older adults with either normal or high cfPWV. Cognitive function was measured via an intensive one-time neuropsychological battery, while cfPWV by applanation tonometry, carotid intima-media thickness and function (i.e., distensibility) by ultrasonography, and cardiorespiratory fitness (i.e., VO₂peak) by a submaximal exercise test. Correlations among age, VO₂peak, carotid intima-media thickness, cfPWV, and cognitive function were performed along with a series of multivariate analyses of variance. Compared with NAS, participants with HAS had greater aortic, carotid, and brachial blood pressures but similar cardiorespiratory fitness and carotid intima-media thickness and distensibility. Participants with NAS exhibited better neuropsychological performance in executive function and attention and overall cognitive function than those with HAS. When controlling for age, visual scanning and perception scores were correlated with cfPWV and VO₂peak. Our findings suggest that certain cognitive domains for older adults are associated with their cardiorespiratory fitness and aortic stiffness.

Monitoring haemodynamic changes in rodent models to better inform safety pharmacology: Novel insights from

Animal models are essential for assessing cardiovascular responses to novel therapeutics. Cardiovascular safety liabilities represent a leading cause of drug attrition and better preclinical measurements are essential to predict drug-related toxicities. Presently, radiotelemetric approaches recording blood pressure are routinely used in preclinical in vivo haemodynamic assessments, providing valuable information on therapy-associated cardiovascular effects. Nonetheless, this technique is chiefly limited to the monitoring of blood pressure and heart rate alone. Alongside these measurements, Doppler flowmetry can provide additional information on the vasculature by simultaneously measuring changes in blood flow in multiple different regional vascular beds. However, due to the time-consuming and expensive nature of this approach, it is not widely used in the industry. Currently, analysis of waveform data obtained from telemetry and Doppler flowmetry typically examines averages or peak values of waveforms. Subtle changes in the morphology and variability of physiological waveforms have previously been shown to be early markers of toxicity and pathology. Therefore, a detailed analysis of pressure and flowmetry waveforms could enhance the understanding of toxicological mechanisms and the ability to translate these preclinical observations to clinical outcomes. In this review, we give an overview of the different approaches to monitor the effects of drugs on cardiovascular parameters (particularly regional blood flow, heart rate and blood pressure) and suggest that further development of waveform analysis could enhance our understanding of safety pharmacology, providing valuable information without increasing the number of in vivo studies needed.

Novel Pressure Wave Separation Analysis for Cardiovascular Function Assessment Highlights Major Role of Aortic Root

Objective

A novel method was presented to separate the central blood pressure wave (CBPW) into five components with different biophysical and temporal origins. It includes a time-varying emission coefficient (γ) that quantifies pulse wave generation and reflection at the aortic root.

Methods

The method was applied to normotensive subjects with modulated physiology by inotropic/vasoactive drugs (n = 13), hypertensive subjects (n = 158), and virtual subjects (n = 4,374).

Results

γ is directly proportional to aortic flow throughout the cardiac cycle. Mean peak γ increased with increasing pulse pressure (from <30 to >70 mmHg) in the hypertensive (from 1.6 to 2.5, P < 0.001) and in silico (from 1.4 to 2.8, P < 0.001) groups, dobutamine dose (from baseline to 7.5 μg/kg/min) in the normotensive group (from 2.1 to 2.7, P < 0.05), and remained unchanged when peripheral wave reflections were suppressed in silico. This was accompanied by an increase in the percentage contribution of the cardiac-aortic-coupling component of CBPW in systole: from 11% to 23% (P < 0.001) in the hypertensive group, 9% to 21% (P < 0.001) in the in silico group, and 17% to 23% (P < 0.01) in the normotensive group.

Conclusion

These results suggest that the aortic root is a major reflection site in the systemic arterial network and ventricular-aortic coupling is the main determinant in the elevation of pulsatile pulse pressure.

Significance

Ventricular-aortic coupling is a prime therapeutic target for preventing/treating systolic hypertension.

Limited value of pulse wave analysis in assessing arterial wave reflection and stiffness in the pulmonary artery

We explored the use of the augmentation index (AI) based on pulse wave analysis (PWA) in the pulmonary circulation as a measure of wave reflection and arterial stiffness in individuals with and without pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). Right heart catheterization was performed using a pressure and Doppler flow sensor-tipped catheter to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in 10 controls, 11 PAH patients, and 11 CTEPH patients. PWA was applied to the measured pressure, while wave intensity analysis (WIA) and wave separation analysis (WSA) were performed using both the pressure and velocity to determine the magnitudes and timings of reflected waves. Type C (AI < 0) pressure waveform dominated in controls and type A (AI > 12%) waveform dominated in PAH patients, while there was a mixture of types A, B, and C among CTEPH patients. AI was greater and the inflection time shorter in CTEPH compared to PAH patients. There was a poor correlation between AI and arterial wave speed as well as measures of wave reflection derived from WIA and WSA. The infection point did not match the timing of the backward compression wave in ~50% of the cases. In patients with type C waveforms, the inflection time correlated well to the timing of the late systolic forward decompression wave caused by ventricular relaxation. In conclusion quantifying pulmonary arterial wave reflection and stiffness using AI based on PWA may be inaccurate and should therefore be discouraged.

Lower-body dynamic exercise reduces wave reflection in healthy young adults

NEW FINDINGS

What is the central question of this study? There is a paradoxical reduction in augmentation index during lower-body dynamic (LBD) exercise in the face of an increase in central pressure. To determine causality, the amplitudes of forward and backward pressure waves were assessed separately using wave separation analysis. What is the main finding and its importance? Reflection magnitude decreased during LBD exercise in healthy young adults and was attributable to an increased forward pressure wave amplitude and decreased backward pressure wave amplitude. This vasoactive response might limit the adverse effects of wave reflection during LBD exercise, optimizing ventricular-arterial interactions.

ABSTRACT

Acute lower-body dynamic (LBD) exercise decreases surrogate measures of wave reflection, such as the augmentation index. However, the augmentation index is influenced by the combined effects of wave reflection timing, magnitude and other confounding factors external to wave reflection, which make it difficult to discern the origin of changes in surrogate measures. The relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to central pressure can be determined by wave separation analysis. Reflection magnitude (RM = Pb/Pf) and the timing of apparent wave reflection return can also be determined. We tested the hypothesis that acute LBD exercise decreases RM and reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 25 adults (24 ± 4 years of age) at baseline and during light-, moderate- and vigorous-intensity exercise. Wave separation analysis was conducted offline using a personalized physiological flow wave to determine Pf, Pb, RM and RWTT. The RM decreased during all intensities of exercise compared with baseline (all P < 0.001; baseline, 43 ± 5%; light, 33 ± 6%; moderate, 23 ± 7%; vigorous, 17 ± 5%). The reduction in RM was attributable to the combined effect of increased Pf and decreased Pb during exercise. The RWTT decreased during all intensities of exercise compared with baseline (all P < 0.04; baseline, 156 ± 17 ms; light, 144 ± 15 ms; moderate, 129 ± 16 ms; vigorous, 121 ± 17 ms). Lastly, in a stepwise multilinear regression, Pf, but not Pb and RWTT, contributed to increased central pulse pressure during LBD exercise. These data show that wave reflection decreased and that central pulse pressure is most influenced by Pf during LBD exercise.

Estimating Central Pulse Pressure From Blood Flow by Identifying the Main Physical Determinants of Pulse Pressure Amplification

Several studies suggest that central (aortic) blood pressure (cBP) is a better marker of cardiovascular disease risk than peripheral blood pressure (pBP). The morphology of the pBP wave, usually assessed non-invasively in the arm, differs significantly from the cBP wave, whose direct measurement is highly invasive. In particular, pulse pressure, PP (the amplitude of the pressure wave), increases from central to peripheral arteries, leading to the so-called pulse pressure amplification (ΔPP). The main purpose of this study was to develop a methodology for estimating central PP (cPP) from non-invasive measurements of aortic flow and peripheral PP. Our novel approach is based on a comprehensive understanding of the main cardiovascular properties that determine ΔPP along the aortic-brachial arterial path, namely brachial flow wave morphology in late systole, and vessel radius and distance along this arterial path. This understanding was achieved by using a blood flow model which allows for workable analytical solutions in the frequency domain that can be decoupled and simplified for each arterial segment. Results show the ability of our methodology to (i) capture changes in cPP and ΔPP produced by variations in cardiovascular properties and (ii) estimate cPP with mean differences smaller than 3.3 ± 2.8 mmHg on in silico data for different age groups (25-75 years old) and 5.1 ± 6.9 mmHg on in vivo data for normotensive and hypertensive subjects. Our approach could improve cardiovascular function assessment in clinical cohorts for which aortic flow wave data is available.

Arterial Stiffness in Aging: Does It Have a Place in Clinical Practice?: Recent Advances in Hypertension

Aortic stiffness increases markedly with age and is associated with excess risk for various adverse clinical outcomes, including heart disease, dementia, and kidney disease. Although evidence for adverse effects of aortic stiffening is overwhelming, integration of direct and indirect measures of aortic stiffness into routine clinical assessment has lagged behind the science. This brief review will examine recent evidence supporting the value of stiffness as an important new risk factor for hypertension and cardiovascular disease and will offer suggestions for incorporating stiffness measures into routine clinical practice.

Dynamic and isometric handgrip exercise increases wave reflection in healthy young adults

Early return and increased magnitude of wave reflection augments pulsatile load, wastes left ventricular effort, and is associated with cardiovascular events. Acute handgrip (HG) exercise increases surrogate measures of wave reflection such as augmentation index. However, augmentation index does not allow distinguishing between timing versus magnitude of wave reflection and is affected by factors other than wave reflection per se. Wave separation analysis decomposes central pressure into relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to calculate reflection magnitude (RM = Pb/Pf) and determine the timing of apparent wave reflection return. We tested the hypothesis that acute dynamic and isometric HG exercise increases RM and decreases reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25 ± 4 yr) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiological flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared with baseline (P = 0.04 and P < 0.01, respectively; baseline 40 ± 5, dynamic 43 ± 6, isometric 43 ± 7%). Meanwhile, RWTT decreased during dynamic and isometric HG exercise compared with baseline (P = 0.03 and P < 0.001, respectively; baseline 164 ± 23, dynamic 155 ± 23, isometric 148 ± 20 ms). Moreover, the changes in RM and RWTT were not different between dynamic and isometric HG exercise. The present data suggest that wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.NEW & NOTEWORTHY This study demonstrated that wave reflection magnitude is increased while reflected wave transit time is decreased during handgrip exercise in healthy young adults. The larger backward pressure waves and earlier return of these pressure waves were not different between dynamic and isometric handgrip exercise. These acute changes in wave reflection during handgrip exercise transiently augment pulsatile load.

Measurement, Analysis and Interpretation of Pressure/Flow Waves in Blood Vessels

The optimal performance of the cardiovascular system, as well as the break-down of this performance with disease, both involve complex biomechanical interactions between the heart, conduit vascular networks and microvascular beds. ‘Wave analysis’ refers to a group of techniques that provide valuable insight into these interactions by scrutinizing the shape of blood pressure and flow/velocity waveforms. The aim of this review paper is to provide a comprehensive introduction to wave analysis, with a focus on key concepts and practical application rather than mathematical derivations. We begin with an overview of invasive and non-invasive measurement techniques that can be used to obtain the signals required for wave analysis. We then review the most widely used wave analysis techniques—pulse wave analysis, wave separation and wave intensity analysis—and associated methods for estimating local wave speed or characteristic impedance that are required for decomposing waveforms into forward and backward wave components. This is followed by a discussion of the biomechanical phenomena that generate waves and the processes that modulate wave amplitude, both of which are critical for interpreting measured wave patterns. Finally, we provide a brief update on several emerging techniques/concepts in the wave analysis field, namely wave potential and the reservoir-excess pressure approach.

Haemodynamics of Hypertension in Children

PURPOSE OF REVIEW

To review the haemodynamic characteristics of paediatric hypertension.

RECENT FINDINGS

Pulsatile components of blood pressure are determined by left ventricular dynamics, aortic stiffness, systemic vascular resistance and wave propagation phenomena. Recent studies delineating these factors have identified haemodynamic mechanisms contributing to primary hypertension in children. Studies to date suggest a role of cardiac over activity, characterized by increased heart rate and left ventricular ejection, and increased aortic stiffness as the main haemodynamic determinants of primary hypertension in children.

Associations between Intrinsic Heart Rate, P Wave and QT Interval Durations and Pulse Wave Analysis in Patients with Hypertension and High Normal Blood Pressure

The present study aimed to explore the relationship between electrocardiographic (ECG) and pulse wave analysis variables in patients with hypertension (HT) and high normal blood pressure (HNBP). A total of 56 consecutive, middle-aged hypertensive and HNBP patients underwent pulse wave analysis and standard 12-lead ECG. Pulse wave velocity (PWV), heart rate, intrinsic heart rate (IHR), P wave and QT interval durations were as follows: 7.26 ± 0.69 m/s, 69 ± 11 beats/minute, 91 ± 3 beats/minute, 105 ± 22 mm and 409 ± 64 mm, respectively. Significant correlations were obtained between PWV and IHR and P wave duration, respectively, between early vascular aging (EVA) and P wave and QT interval durations, respectively. Linear regression analysis revealed significant associations between ECG and pulse wave analysis variables but multiple regression analysis revealed only IHR as an independent predictor of PWV, even after adjusting for blood pressure variables and therapy. Receiver-operating characteristic (ROC) curve analysis revealed P wave duration (area under curve (AUC) = 0.731; 95% CI: 0.569-0.893) as a predictor of pathological PWV, and P wave and QT interval durations were found as sensitive and specific predictors of EVA. ECG provides information about PWV and EVA in patients with HT and HNBP. IHR and P wave durations are independent predictors of PWV, and P wave and QT interval may predict EVA.

Influence of Renal Transplantation and Living Kidney Donation on Large Artery Stiffness and Peripheral Vascular Resistance

BACKGROUND

Vascular status following renal transplantation (RT) may improve while living kidney donation (LKD) is possibly associated with an increased cardiovascular risk.

METHODS

We prospectively assessed glomerular filtration rate (mGFR, 51Chrome EDTA clearance) and intermediate vascular risk factors in terms of blood pressure (BP), pulse wave velocity (PWV), central augmentation index (AIx), excess pressure (Pexcess), and forearm vascular resistance in donors (n = 58, 45 ± 13 years) and recipients (n = 51, 50 ± 12 years) before and one year following LKD or RT.

RESULTS

After kidney donation, mGFR decreased by 33% to 65 ± 11 ml/min/1.73m2, while recipients obtained a mGFR of 55 ± 9 ml/min/1.73m.2 Ambulatory 24-hour mean arterial BP (MAP) remained unchanged in donors but decreased by 5 mm Hg in recipients (P < 0.05). Carotid-femoral PWV increased by 0.3 m/s in donors (P < 0.05) but remained unchanged in recipients. AIx was unaltered after LKD but decreased following RT (P < 0.01), and Pexcess did not change in either group. Resting forearm resistance (Rrest), measured by venous occlusion plethysmography, increased after LKD (P < 0.05) but was unaffected by RT, while no changes were seen in minimum resistance (Rmin). ΔPWV showed a positive linear association to Δ24-hour MAP in both groups. Multiple linear regression analysis (adjusting for age, gender, and the baseline value of the studied parameter) did not detect independent effects of graft function on 24-hour MAP, PWV, AIx, vascular resistance, or Pexcess, whereas low post-donation GFR was related to higher AIx and Rrest.

CONCLUSIONS

RT reduced BP and AIx without affecting PWV, whereas LKD resulted in increased PWV and Rrest, despite unchanged BP.

Exaggerated Aortic Pulse Pressure and Wave Amplitude During Muscle Metaboreflex Activation in Type 2 Diabetes Patients

BACKGROUND

Peripheral mean arterial pressure (MAP) responses to muscle metaboreflex activation using postexercise muscle ischemia (PEMI) in type 2 diabetes patients (T2D) are contradictory. Given that aortic pulse pressure (PP) and wave reflections are better indicators of cardiac load than peripheral MAP, we evaluated aortic blood pressure (BP) and wave amplitude during PEMI.

METHODS

Aortic BP and pressure wave amplitudes were measured at rest and during PEMI following isometric handgrip at 30% maximum voluntary contraction (MVC) in 16 T2D and 15 controls. Resting aortic stiffness (carotid-femoral pulse wave velocity, cfPWV) and fasting blood glucose (FBG) were measured.

RESULTS

Increases in aortic MAP (Δ26 ± 2 mmHg vs. Δ17 ± 2 mmHg), PP (Δ15 ± 2 mmHg vs. Δ10 ± 1 mmHg), augmentation index (AIx) (Δ8.2 ± 1.0% vs. Δ4.5 ± 1.3%), augmented pressure (AP) (Δ11 ± 1 mmHg vs. Δ5 ± 1 mmHg), forward (Pf) (Δ9 ± 1 mmHg vs. Δ5 ± 1 mmHg), and backward pressure waves (Pb) (Δ10 ± 1 mmHg vs. Δ5 ± 1 mmHg) responses to PEMI were greater in T2D than controls (P < 0.05). Aortic PP, but not MAP, response to PEMI was correlated to Pf (r = 0.63, P < 0.001) and Pb (r = 0.82, P < 0.001) responses and cfPWV (r = 0.37, P < 0.05).

CONCLUSIONS

Aortic BP and pressure wave responses to muscle metaboreflex activation are exaggerated in T2D. Aortic PP during PEMI was related to increased wave reflection, forward wave amplitude, and aortic stiffness in T2D patients.

Clinical Correlates of Aortic Stiffness and Wave Amplitude in Black Men and Women in the Community

Background

Black individuals have greater risk for cardiovascular disease (CVD) than whites. Identifying CVD risk factors associated with abnormal aortic hemodynamics in blacks may optimize CVD prevention and treatment strategies.

Methods and Results

Jackson Heart Study participants underwent applanation tonometry (2011–2016) with assessment of carotid‐femoral pulse wave velocity (CFPWV) and forward wave amplitude (FWA). CVD risk factors were assessed during examination 3 (2009–2012). We examined the association of risk factors with binary and continuous CFPWV and FWA in multivariable stepwise models. We evaluated for effect modification by sex to determine differential associations of risk factors with aortic hemodynamics in men and women. We examined 1322 individuals (mean age 66±11 years, 66% women). Age was strongly associated with elevated CFPWV (odds ratio, 4.76; 95% confidence interval, 3.84–5.89 [P<0.0001]) and FWA (odds ratio, 2.30; 95% CI, 1.98–2.69 [P<0.0001]). Men had greater odds of elevated CFPWV compared with women (odds ratio, 1.54; 95% confidence interval, 1.11–2.13 [P=0.009]). Heart rate, mean arterial pressure, and use of antihypertensive medications were associated with elevated CFPWV and FWA (all P≤0.02). Additionally, total/high‐density lipoprotein cholesterol and fasting glucose were associated with elevated CFPWV (both P≤0.002) and use of diabetes mellitus medications was associated with elevated FWA (P≤0.0001). We observed a steeper association of age and mean arterial pressure with unfavorable aortic hemodynamics in women than men.

Conclusions

In blacks in the community, differential CVD risk factors are associated with aortic stiffness and FWA. Future work may determine the impact of risk factor modification on abnormal central aortic hemodynamics and CVD outcomes.

Hemodynamic Mechanism of the Age-Related Increase in Pulse Pressure in Women

Supplemental Digital Content is available in the text.

We examined the influence of arterial stiffening and ventricular ejection dynamics on the age-related increase in central pulse pressure. A total of 2033 women aged 18 to 91 years from the Twins UK cohort were studied. Aortic flow and central blood pressure were measured by Doppler sonography and carotid tonometry, respectively. Measured values of central pulse pressure were compared with values predicted from aortic pulse wave velocity and ventricular ejection characteristics. Central pulse pressure at the first shoulder (P1) increased with age from 29.2±8.0 in those <40 years to 44.2±13.8 mm Hg in those >70 years (means±SD; P<0.001), an increase explained almost entirely by the concomitant increase in aortic pulse wave velocity. Pulse pressure, at the second pressure peak (P2, usually equal to peak central pulse pressure) increased to a greater extent with age: from 29.1±7.8 mm Hg for those <40 years to 60.2±20.5 mm Hg for those >70 years (P<0.001). The ratio of P2/P1 closely mirrored the ratio of ejection volume to ejection velocity at corresponding time points, and the proportionately greater increase in P2 compared with P1 was explained by increased ventricular ejection up to the time of P2. This increased from 52.5±13.1 to 59.3±17.8 mL (P<0.001) in parallel with an age-related increase in stroke volume and body mass index. These results suggest that the age-related change in central pulse wave morphology is driven mainly by an increase in arterial stiffening and altered pattern of ventricular ejection.

Arterial stiffness and peripheral vascular resistance in offspring of hypertensive parents: influence of sex and other confounders

AIM

Established essential hypertension is associated with increased arterial stiffness and peripheral resistance, but the extent of vascular changes in persons genetically predisposed for essential hypertension is uncertain.

METHODS

Participants from the Danish Hypertension Prevention Project (DHyPP) (both parents hypertensive) (n = 95, 41 ± 1 years, 53% men) were compared with available spouses (n = 45, 41 ± 1 years) using measurements of ambulatory blood pressure (BP), left ventricular mass index (LVMI), pulse wave velocity, central BP and augmentation index (AIx) in addition to forearm resting and minimal resistance [forearm resting vascular resistance (Rrest) and forearm minimal vascular resistance (Rmin)].

RESULTS

DHyPP patients with participating spouses had higher 24-h mean BP (94 ± 1 vs. 88 ± 1 mmHg, P < 0.01), LVMI (94 ± 3 vs. 80 ± 2 g/m, P < 0.01), central SBP (121 ± 2 vs. 111 ± 2 mmHg, P < 0.01) and AIx (16.0 ± 1.2 vs. 10.5 ± 1.7%, P < 0.01), but similar carotid-femoral pulse wave velocity (7.5 ± 0.2 vs. 7.1 ± 0.2 m/s), Rrest (53 ± 3 vs. 51 ± 3 mmHg/ml/min/100 ml) and log Rmin (0.58 ± 0.02 vs. 0.55 ± 0.02 mmHg/ml/min/100 ml) when compared with spouses. Using multiple linear regression analysis (adjusting for sex, age, BMI, creatinine clearance and 24-h BP, heart rate and sodium excretion) AIx and LVMI remained elevated in DHyPP patients [4.2% (0.7; 7.7), P = 0.02 and 6.3 g/m (0.7; 11.9), P = 0.03]. For the entire DHyPP cohort AIx, Rrest and Rmin were higher in women than men (P < 0.01), and the same was true for AIx and Rmin among spouses (P < 0.05). Furthermore, AIx was linearly associated with Rrest and Rmin.

CONCLUSION

Young to middle-aged individuals genetically predisposed for essential hypertension display increased AIx and LVMI, although vascular stiffness and peripheral resistance are still normal.

Reduced Aortic Distensibility is Associated With Higher Aorto-Carotid Wave Transmission and Central Aortic Systolic Pressure in Young Adults After Coarctation Repair

Background The long-term prognosis of patients with repaired aortic coarctation is characterized by high rates of cardiovascular and cerebrovascular disease related to hypertension, the basis of which remains unclear. To define potential underlying mechanisms, we investigated aortic and carotid arterial biomechanics and wave dynamics, and determinants of aortic systolic blood pressure, in young adults after coarctation repair. Methods and Results Aortic arch and carotid biomechanics, wave intensity and wave power, and central aortic blood pressure, were derived from echocardiography and brachial blood pressure in 43 young adults after coarctation repair and 42 controls. Coarctation subjects had higher brachial and central systolic blood pressure ( P=0.04), while aortic compliance was lower and characteristic impedance (Zc) higher. Although carotid intima-media thickness was higher ( P<0.001), carotid biomechanics were no different. Carotid forward compression wave power was higher and was negatively correlated with aortic compliance ( R2=0.42, P<0.001) and distensibility ( R2=0.37, P=0.001) in coarctation subjects. Aortic wave power and wave reflection indices were no different in control and coarctation patients, but coarctation patients with elevated aortic Zc had greater aorto-carotid transmission of forward compression wave power ( P=0.006). Aortic distensibility was the only independent predictor of central aortic systolic blood pressure on multivariable analysis. Conclusions Young adults following coarctation repair had a less compliant aorta, but no change in carotid biomechanics. Reduced aortic distensibility was related to greater transmission of aortic forward wave energy into the carotid artery and higher central aortic systolic blood pressure. These findings suggest that reduced aortic distensibility may contribute to later cardiovascular and cerebrovascular disease after coarctation repair.

Changes in contractility determine coronary haemodynamics in dyssynchronous left ventricular heart failure, not vice versa

BACKGROUND

Biventricular pacing has been shown to increase both cardiac contractility and coronary flow acutely but the causal relationship is unclear. We hypothesised that changes in coronary flow are secondary to changes in cardiac contractility. We sought to examine this relationship by modulating coronary flow and cardiac contractility.

METHODS

Contractility and lusitropy were altered by varying the location of pacing in 8 patients. Coronary autoregulation was transiently disabled with intracoronary adenosine. Simultaneous coronary flow velocity, coronary pressure and left ventricular pressure data were measured in the different pacing settings with and without hyperaemia and wave intensity analysis performed.

RESULTS

Multisite pacing was effective at altering left ventricular contractility and lusitropy (pos. dp/dtmax -13% to +10% and neg. dp/dtmax -15% to +17% compared to baseline). Intracoronary adenosine decreased microvascular resistance (362.5 mm Hg/s/m to 156.7 mm Hg/s/m, p < 0.001) and increased LAD flow velocity (22 cm/s vs 45 cm/s, p < 0.001) but did not acutely change contractility or lusitropy. The magnitude of the dominant accelerating wave, the Backward Expansion Wave, was proportional to the degree of contractility as well as lusitropy (r = 0.47, p < 0.01 and r = -0.50, p < 0.01). Perfusion efficiency (the proportion of accelerating waves) increased at hyperaemia (76% rest vs 81% hyperaemia, p = 0.04). Perfusion efficiency correlated with contractility and lusitropy at rest (r = 0.43 & -0.50 respectively, p = 0.01) and hyperaemia (r = 0.59 & -0.6, p < 0.01).

CONCLUSIONS

Acutely increasing coronary flow with adenosine in patients with systolic heart failure does not increase contractility. Changes in coronary flow with biventricular pacing are likely to be a consequence of enhanced cardiac contractility from resynchronization and not vice versa.

Myocardial preload alters central pressure augmentation through changes in the forward wave

OBJECTIVE

Augmentation index (AIx) is often used to quantify the contribution of wave reflection to central pulse pressure. Recent studies have challenged this view by showing how contractility-induced changes in the forward pressure wave can markedly impact AIx. We hypothesized that changes in preload will also affect AIx through changes in the forward wave and studied this in two experiments.

METHODS

Noninvasively obtained aortic pressure was used to study central haemodynamics and wave morphology. In the first experiment, we examined the effects of head-up tilt with and without unilateral thigh cuff in 12 young healthy volunteers (mean age 26 years, 50% men). In the second experiment, we examined the effects of active standing in 31 middle-aged patients (mean age 57 years, 65% men) before and after phlebotomy.

RESULTS

Head-up tilt or active standing significantly decreased AIx [-17.7 ± 10.4 percentage point (pp) in the young population, -4.7 ± 12.3 pp in the middle-aged population, both P < 0.05]. The fall in AIx was associated with increases in HR, diastolic pressure and systemic vascular resistance and a decrease in stroke volume (all P < 0.05). Inflation of a unilateral thigh cuff reduced the decrease in AIx by 10.7 pp, whereas 500 ml of blood loss augmented the fall in AIx by 5.9 pp (both P < 0.05). The changes in AIx were related to a preload-induced change in forward pressure wave shape (earlier peaking and steeper downstroke).

CONCLUSION

Next to inotropic and chronotropic effects, preload emerges as another myocardial factor that obscures the relation between wave reflection and AIx.

Menstrual phase and the vascular response to acute resistance exercise

INTRODUCTION

Aerobic exercise has a favorable effect on systemic vascular function, reducing both central (large elastic artery) and peripheral (smaller muscular artery) stiffness. The effects of resistance exercise (RE) on arterial stiffness are more complex. Acute RE increases central artery stiffness while decreasing peripheral stiffness. To date, the majority of studies have been performed in predominantly male participants.

PURPOSE

To examine the effect of acute RE on central and peripheral arterial stiffnesses in women, a secondary purpose was to explore the influence of cyclic changes in estrogen status across the menstrual cycle on the arterial response to acute RE.

METHODS

18 healthy women [28 ± 7 years, body mass index (BMI) 22.6 ± 2.9 kg/m²] completed an acute RE bout during the early follicular and the early luteal phase of their menstrual cycle. Salivary 17β-Estradiol concentration was measured during each phase, using a passive drool technique. Pulse-wave velocity (PWV) was obtained from the carotid-femoral and carotid-radial pulse sites to measure central and peripheral stiffness, respectively, using applanation tonometry. PWV was measured at rest, immediately, 10, 20, and 30 min post-RE.

RESULTS

17β-Estradiol concentration was significantly lower in the early follicular vs. the early luteal phase of the menstrual cycle (1.78 ± 0.51 vs. 2.40 ± 0.26 pg/ml, p = 0.01). Central PWV significantly increased (p < 0.05) and peripheral PWV significantly decreased (p < 0.05) post-RE in both the early follicular and early luteal phases. No phase-by-time interaction was detected for either vascular segment (p > 0.05).

CONCLUSION

Women experience increases in central arterial stiffness and reductions in peripheral arterial stiffness following acute RE. Menstrual cycle phase may not influence changes in arterial stiffness in response to acute RE.

Slim Body Weight Is Highly Associated With Enhanced Lipoprotein Functionality, Higher HDL-C, and Large HDL Particle Size in Young Women

There has been no information about the correlations between body weight distribution and lipoprotein metabolism in terms of high-density lipoproteins-cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP). In this study, we analyzed the quantity and quality of HDL correlations in young women (21.5 ± 1.2-years-old) with a slim (n = 21, 46.2 ± 3.8 kg) or plump (n = 30, 54.6 ± 4.4 kg) body weight. Body weight was inversely correlated with the percentage of HDL-C in total cholesterol (TC). The plump group showed 40% higher body fat (26 ± 3 %) and 86% more visceral fat mass (VFM, 1.3 ± 0.3 kg) than the slim group, which showed 18 ± 2% body fat and 0.7 ± 0.2 kg of VFM. Additionally, the plump group showed 20% higher TC, 58% higher triglyceride (TG), and 12% lower HDL-C levels in serum. The slim group showed 34% higher apoA-I but 15% lower CETP content in serum compared to the plump group. The slim group showed a 13% increase in particle size and 1.9-fold increase in particle number with enhanced cholesterol efflux activity. Although the plump group was within a normal body mass index (BMI) range, its lipid profile and lipoprotein properties were distinctly different from those of the slim group in terms of CETP mass and activity, HDL functionality, and HDL particle size.

Identifying Hemodynamic Determinants of Pulse Pressure: A Combined Numerical and Physiological Approach

We examined the ability of a simple reduced model comprising a proximal characteristic impedance linked to a Windkessel element to accurately predict central pulse pressure (PP) from aortic blood flow, verified that parameters of the model corresponded to physical properties, and applied the model to examine PP dependence on cardiac and vascular properties. PP obtained from the reduced model was compared with theoretical values obtained in silico and measured values in vivo. Theoretical values were obtained using a distributed multisegment model in a population of virtual (computed) subjects in which cardiovascular properties were varied over the pathophysiological range. In vivo measurements were in normotensive subjects during modulation of physiology with vasoactive drugs and in hypertensive subjects. Central PP derived from the reduced model agreed with theoretical values (mean difference±SD, -0.09±1.96 mm Hg) and with measured values (mean differences -1.95±3.74 and -1.18±3.67 mm Hg for normotensive and hypertensive subjects, respectively). Parameters extracted from the reduced model agreed closely with theoretical and measured physical properties. Central PP was seen to be determined mainly by total arterial compliance (inversely associated with central arterial stiffness) and ventricular dynamics: the blood volume ejected by the ventricle into the aorta up to time of peak pressure and blood flow into the aorta (corresponding to the rate of ventricular ejection) up to this time point. Increased flow and volume accounted for 20.1 mm Hg (52%) of the 39.0 mm Hg difference in PP between the upper and lower tertiles of the hypertensive subjects.

Computational assessment of model-based wave separation using a database of virtual subjects

The quantification of arterial wave reflection is an important area of interest in arterial pulse wave analysis. It can be achieved by wave separation analysis (WSA) if both the aortic pressure waveform and the aortic flow waveform are known. For better applicability, several mathematical models have been established to estimate aortic flow solely based on pressure waveforms. The aim of this study is to investigate and verify the model-based wave separation of the ARCSolver method on virtual pulse wave measurements. The study is based on an open access virtual database generated via simulations. Seven cardiac and arterial parameters were varied within physiological healthy ranges, leading to a total of 3325 virtual healthy subjects. For assessing the model-based ARCSolver method computationally, this method was used to perform WSA based on the aortic root pressure waveforms of the virtual patients. Asa reference, the values of WSA using both the pressure and flow waveforms provided by the virtual database were taken. The investigated parameters showed a good overall agreement between the model-based method and the reference. Mean differences and standard deviations were -0.05±0.02AU for characteristic impedance, -3.93±1.79mmHg for forward pressure amplitude, 1.37±1.56mmHg for backward pressure amplitude and 12.42±4.88% for reflection magnitude. The results indicate that the mathematical blood flow model of the ARCSolver method is a feasible surrogate for a measured flow waveform and provides a reasonable way to assess arterial wave reflection non-invasively in healthy subjects.

Enhanced Aortic Reflected Wave Magnitude Accounts for the Impact of Female Gender on Aortic Pressure Augmentation in a Group of African Ancestry

BACKGROUND

Aortic reflected wave magnitude (RM) may not account for sex-specific differences in aortic pressure augmentation in Caucasians. However, aortic reflected waves are greater in groups of African descent than other ethnic groups. We determined whether RM or alternative factors explain the impact of sex on aortic augmented pressure (Pa) in participants of African ancestry.

METHODS

We assessed aortic function (radial applanation tonometry, SphygmoCor) in 1,197 randomly recruited community participants of African ancestry (age ≥ 16 years). Aortic forward (Pf) and backward (Pb) wave separation was performed assuming an aortic triangular flow wave validated against aortic velocity measurements.

RESULTS

Across the adult lifespan, women had greater multivariate-adjusted augmentation index (AIx) and Pa. This was associated with multivariate-adjusted age-related increases in Pb, RM (Pb/Pf), and time to the peak of Pf and decreases in backward wave foot time; but not increases in Pf. With adjustors, Pa was associated with female gender (β-coefficient = 3.81 ± 0.34), a relationship which was markedly attenuated by adjustments for RM (β-coefficient = 1.78 ± 0.31, P < 0.0001 vs. without adjustments for RM), and Pb (β-coefficient = 2.05 ± 0.19, P < 0.0001 vs. without adjustments for Pb), but not by adjustments for Pf, time to the peak of Pf, or backward wave foot time. Similarly, AIx was associated with female gender, a relationship which was markedly attenuated by adjustments for RM, Pb, and backward wave foot time, but not alternative factors.

CONCLUSIONS

In contrast to reports in alternative populations, the relationship between aortic pressure augmentation and female gender in participants of African descent is accounted for mainly by increases in RM.

Wave intensity of aortic root pressure as diagnostic marker of left ventricular systolic dysfunction

Background

Systolic left ventricular function strongly influences the blood pressure waveform. Therefore, pressure-derived parameters might potentially be used as non-invasive, diagnostic markers of left ventricular impairment. The aim of this study was to investigate the performance of pressure-based parameters in combination with electrocardiography (ECG) for the detection of left ventricular systolic dysfunction defined as severely reduced ejection fraction (EF).

Methods and results

Two populations, each comprising patients with reduced EF and pressure-matched controls, were included for the main analysis (51/102 patients) and model testing (44/88 patients). Central pressure was derived from radial readings and used to compute blood flow. Subsequently, pulse wave analysis and wave intensity analysis were performed and the ratio of the two peaks of forward intensity (SDR) was calculated as a novel index of ventricular function. SDR was significantly decreased in the reduced EF group (2.5 vs. 4.4, P<0.001), as was central pulse pressure, augmentation index and ejection duration (ED), while the QRS-duration was prolonged. SDR and ED were independent predictors of ventricular impairment and when combined with QRS in a simple decision tree, a reduced EF could be detected with a sensitivity of 92% and a specificity of 80%. The independent power of ED, SDR and QRS to predict reduced EF was furthermore confirmed in the test population.

Conclusion

The detection or indication of reduced ejection fraction from pressure-derived parameters seems feasible. These parameters could help to improve the quality of cardiovascular risk stratification or might be used in screening strategies in the general population.

High-Intensity Interval Cycling Exercise on Wave Reflection and Pulse Wave Velocity

Kingsley, JD, Tai, YL, Vaughan, J, and Mayo, X. High-intensity interval cycling exercise on wave reflection and pulse wave velocity. J Strength Cond Res 31(5): 1313-1320, 2017-The purpose of this study was to assess the effects of high-intensity exercise on wave reflection and aortic stiffness. Nine young, healthy men (mean ± SD: age: 22 ± 2 years) participated in the study. The high-intensity interval cycling exercise consisted of 3 sets of Wingate Anaerobic Tests (WATs) with 7.5% of bodyweight as resistance and 2 minutes of rest between each set. Measurements were taken at rest and 1 minute after completion of the WATs. Brachial and aortic blood pressures, as well as wave reflection characteristics, were measured through pulse wave analysis. Aortic stiffness was assessed through carotid-femoral pulse wave velocity (cfPWV). A repeated-measures analysis of variance was used to investigate the effects of the WATs on blood pressure and vascular function across time. There was no change in brachial or aortic systolic pressure from rest to recovery. There was a significant (p ≤ 0.05) decrease in brachial diastolic pressure (rest: 73 ± 6 mm Hg; recovery: 67 ± 9 mm Hg) and aortic diastolic pressure (rest: 75 ± 6 mm Hg; recovery: 70 ± 9 mm Hg) from rest to recovery. In addition, there was no significant change in the augmentation index (rest: 111.4 ± 6.5%; recovery: 109.8 ± 5.8%, p = 0.65) from rest to recovery. However, there was a significant (p ≤ 0.05) increase in the augmentation index normalized at 75 b·min (rest: 3.29 ± 9.82; recovery 21.21 ± 10.87) during recovery compared with rest. There was no change in cfPWV (rest: 5.3 ± 0.8 m·s; recovery: 5.7 ± 0.5m·s; p = 0.09) in response to the WAT. These data demonstrate that high-intensity interval cycling exercise with short rest periods has a nonsignificant effect on vascular function.

Effects of organic and inorganic nitrate on aortic and carotid haemodynamics in heart failure with preserved ejection fraction

AIMS

To assess the haemodynamic effects of organic vs. inorganic nitrate administration among patients with heart failure with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

We assessed carotid and aortic pressure-flow relations non-invasively before and after the administration of 0.4 mg of sublingual nitroglycerin (n = 26), and in a separate sub-study, in response to 12.9 mmoL of inorganic nitrate (n = 16). Nitroglycerin did not consistently reduce wave reflections arriving at the proximal aorta (change in real part of reflection coefficient, 1st harmonic: -0.09; P = 0.01; 2nd harmonic: -0.045, P = 0.16; 3rd harmonic: +0.087; P = 0.05), but produced profound vasodilatation in the carotid territory, with a significant reduction in systolic blood pressure (133.6 vs. 120.5 mmHg; P = 0.011) and a marked reduction in carotid bed vascular resistance (19 580 vs. 13 078 dynes · s/cm⁵ ; P = 0.001) and carotid characteristic impedance (3440 vs. 1923 dynes · s/cm⁵ ; P = 0.002). Inorganic nitrate, in contrast, consistently reduced wave reflections across the first three harmonics (change in real part of reflection coefficient, 1st harmonic: -0.12; P = 0.03; 2nd harmonic: -0.11, P = 0.01; 3rd harmonic: -0.087; P = 0.09) and did not reduce blood pressure, carotid bed vascular resistance, or carotid characteristic impedance (P = NS).

CONCLUSIONS

Nitroglycerin produces marked vasodilatation in the carotid circulation, with a pronounced reduction in blood pressure and inconsistent effects on central wave reflections. Inorganic nitrate, in contrast, produces consistent reductions in wave reflections, and unlike nitroglycerin, it does so without significant hypotension or cerebrovascular dilatation. These haemodynamic differences may underlie the different effects on exercise capacity and side effect profile of inorganic vs. organic nitrate in HFpEF.

Reduced First-Phase Ejection Fraction and Sustained Myocardial Wall Stress in Hypertensive Patients With Diastolic Dysfunction: A Manifestation of Impaired Shortening Deactivation That Links Systolic to Diastolic Dysfunction and Preserves Systolic Ejection Fraction

Impaired shortening deactivation of cardiac myocytes could sustain myocardial contraction, preserving ejection fraction at the expense of diastolic dysfunction. We examined the relationship between first-phase ejection fraction (EF1), the fraction of left ventricular volume ejected from the start of systole to the time of the first peak in left ventricular pressure (corresponding to the time of maximal ventricular shortening) to the duration of myocardial contraction and diastolic function in patients with hypertension (n=163), and varying degrees of diastolic dysfunction. Left ventricular systolic pressure was estimated by carotid tonometry; time-resolved left ventricular cavity and wall volume were obtained by echocardiography with speckle wall tracking. Measurements were repeated after nitroglycerin, a drug known to influence ventricular dynamics, in a subsample (n=18) of patients. EF1 and time of onset of ventricular relaxation (as determined from the temporal pattern of myocardial wall stress) were independently correlated with diastolic relaxation as measured by tissue Doppler early diastolic mitral annular velocity (E', standardized regression coefficients 0.48 and -0.34 for EF1 and time of onset of ventricular relaxation, respectively, each P<0.001, irrespective of adjustment for age, sex, antihypertensive treatment, measures of afterload, and ventricular geometry) and with diastolic function measured by the ratio of transmitral Doppler early filling velocity (E) to E' (E/E', regression coefficients -0.34 and 0.34, respectively, each P<0.001). Nitroglycerin increased EF1, decreased time of onset of ventricular relaxation, and improved diastolic function (each P<0.05). Hypertensive patients with diastolic dysfunction exhibit reduced EF1 which may sustain myocardial contraction, preserving systolic ejection fraction at the expense of impaired diastolic function.

Arterial-ventricular coupling and parameters of vascular stiffness in hypertensive patients: Role of gender

Objective

Non-invasive estimation of arterial–ventricular coupling has been extensively used for the evaluation of cardiovascular performance, however, a relative small amount of data is available regarding arterial–ventricular coupling and its components in hypertension. The present study was designed to investigate the relationship between left ventricular elastance, arterial elastance, parameters of vascular stiffness and the influence of gender in a population of hypertensive individuals.

Methods

In 102 patients, trans-thoracic cardiac ultrasound, parameters of aortic stiffness (carotid-femoral pulse wave velocity) and wave reflection (augmentation index) were recorded. Ultrasound images of common carotid arteries were acquired for the assessment of intima-media thickness as well as carotid compliance and distensibility coefficient.

Results

Mean age was 61 years, 32% diabetes, 56% dyslipidemia, 9% previous cardiovascular events; women (n = 32) and men were superimposable for cardiovascular risk factors prevalence. In the population, ventricular elastance was significantly correlated with arterial elastance (r = 0.887), age (r = 0.334), gender (r = −0.494), BMI (r = −0.313), augmentation index (r = 0.479) (all p < 0.001); and with carotid compliance and distensibility coefficient (r = 0.229 and r = − 0.250, respectively, both p < 0.05); however, only arterial elastance and gender were independently associated with ventricular elastance in multiple regression models adjusted for confounding factors. Gender-specific analysis revealed that arterial elastance and augmentation index remained statistically significant associated with ventricular elastance in men (r = 0.275, p = 0.04); instead augmentation index was no longer significant (r = 0.052, p = 0.77) in the female sex.

Conclusions

In hypertensive patients, main determinants of ventricular elastance are arterial elastance, as an integrated index of arterial vascular load, and gender; however, pressure augmentation might play an additional role in men.

Computational assessment of hemodynamics-based diagnostic tools using a database of virtual subjects: Application to three case studies

Many physiological indexes and algorithms based on pulse wave analysis have been suggested in order to better assess cardiovascular function. Because these tools are often computed from in-vivo hemodynamic measurements, their validation is time-consuming, challenging, and biased by measurement errors.

Recently, a new methodology has been suggested to assess theoretically these computed tools: a database of virtual subjects generated using numerical 1D-0D modeling of arterial hemodynamics. The generated set of simulations encloses a wide selection of healthy cases that could be encountered in a clinical study.

We applied this new methodology to three different case studies that demonstrate the potential of our new tool, and illustrated each of them with a clinically relevant example: (i) we assessed the accuracy of indexes estimating pulse wave velocity; (ii) we validated and refined an algorithm that computes central blood pressure; and (iii) we investigated theoretical mechanisms behind the augmentation index.

Our database of virtual subjects is a new tool to assist the clinician: it provides insight into the physical mechanisms underlying the correlations observed in clinical practice.

Can arterial wave augmentation in young adults help account for variability of cardiovascular risk in different British ethnic groups?

OBJECTIVE

Traditional cardiovascular risk factors do not fully account for ethnic differences in cardiovascular disease. We tested if arterial function indices, particularly augmentation index (AIx), and their determinants from childhood could underlie such ethnic variability among young British adults in the 'DASH' longitudinal study.

METHODS

DASH, at http://dash.sphsu.mrc.ac.uk/, includes representative samples of six main British ethnic groups. Pulse wave velocity (PWV) and AIx were recorded using the Arteriograph device at ages 21-23 years in a subsample (n = 666); psychosocial, anthropometric, and blood pressure (BP) measures were collected then and in two previous surveys at ages 11-13 years and 14-16 years. For n = 334, physical activity was measured over 5 days (ActivPal).

RESULTS

Unadjusted values and regression models for PWVs were similar or lower in ethnic minority than in White UK young adults, whereas AIx was higher - Caribbean (14.9, 95% confidence interval 12.3-17.0%), West African (15.3, 12.9-17.7%), Indian (15.1, 13.0-17.2%), and Pakistani/Bangladeshi (15.7, 13.7-17.7%), compared with White UK (11.9, 10.2-13.6%). In multivariate models, adjusted for sex, central SBP, height, and heart rate, Indian and Pakistani/Bangladeshi young adults had higher AIx (β = 3.35, 4.20, respectively, P < 0.01) than White UK with a similar trend for West Africans and Caribbeans but not statistically significant. Unlike PWV, physical activity, psychosocial or deprivation measures were not associated with AIx, with borderline associations from brachial BP but no other childhood variables.

CONCLUSION

Early adult AIx, but not arterial stiffness, may be a useful tool for testing components of excess cardiovascular risk in some ethnic minority groups.

Ethnic Differences in Arterial Wave Reflection Are Mostly Explained by Differences in Body Height - Cross-Sectional Analysis of the HELIUS Study

BACKGROUND

Differences in arterial wave reflection and central blood pressure (BP) have been associated with cardiovascular disease (CVD) in various populations and may contribute to ethnic differences in CVD. Whether ethnic differences in wave reflection and central BP can be explained by conventional risk factors for CVD or may result from physiological differences remains undetermined.

METHODS

We examined ethnic differences in augmentation index (AIx) and central systolic BP and their determinants in a large multi-ethnic cohort study in Amsterdam, the Netherlands. A total of 8812 (46% male) participants aged 18-70 years of Dutch, South-Asian Surinamese, African Surinamese and Ghanaian origin were included. AIx and central BP were measured in duplicate using the Arteriograph system.

RESULTS

AIx and central systolic BP were significantly higher in South-Asian Surinamese (35±17%, 126±22 mmHg), African Surinamese (33±17%, 129±23 mmHg) and Ghanaian (33±16%, 135±24 mmHg) as compared with Dutch (27±17%, 118±20 mmHg, all p<0.001). Correction for cardiovascular risk factors only slightly reduced the difference in AIx, whereas correction for body height attenuated age and gender corrected ethnic differences in AIx the most. Differences in central systolic BP were primarily determined by differences in AIx for South-Asian Surinamese and by differences in peripheral systolic BP for subjects of African origin.

CONCLUSIONS

Substantial differences in AIx and central BP exist across different ethnic groups that cannot be explained by differences in conventional risk factors for CVD. These findings may explain part of the underestimation of cardiovascular risk observed in populations of African and South-Asian descent.

Post-exercise effects on aortic wave reflection derived from wave separation analysis in young- to middle-aged pre-hypertensives and hypertensives

PURPOSE

Decreases in brachial blood pressure (BP) may occur for several hours following a bout of exercise. Although aortic backward waves predict cardiovascular damage independent of brachial BP, whether decreases in aortic backward waves also occur post-exercise in young-to-middle-aged hypertensives, the extent to which these changes exceed brachial BP changes, and the best method of identifying these changes is uncertain.

METHODS

We examined aortic function at baseline and 15-min post-exercise in 20 pre-hypertensive or hypertensive men and women (age 45 ± 7 years). Central aortic pressure, forward (Pf) and backward (Pb) wave pressures, the reflection index (RI) and augmentation pressure (AP) and index (AIx) were determined using applanation tonometry, and SphygmoCor software.

RESULTS

Decreases in central aortic (p < 0.001) but not brachial systolic BP and pulse pressure (PP) occurred post-exercise. In addition, decreases in post-exercise (baseline versus post-exercise) Pb (19 ± 4 vs 13 ± 3 mm Hg p < 0.0001), RI (72.9 ± 22.1 vs 47.6 ± 12.8 %, p < 0.0001), AIx (26.3 ± 10.8 vs 7.8 ± 11.6 %, p < 0.0001) and AP (9.9 ± 3.9 vs 2.8 ± 3.9 mm Hg, p < 0.0001), but not Pf, were noted. However, decreases in AIx were not correlated with decreases in Pb, and whilst decreases in aortic PP correlated with decreases in Pb (p < 0.0001), no correlations were noted with decreases in AP or AIx.

CONCLUSION

In young-to-middle-aged pre-hypertensive and hypertensive individuals, aortic backward waves decrease post-exercise; this change is not reflected in brachial BP measurements and is poorly indexed by measures of pressure augmentation.

Evaluating the Hemodynamic Basis of Age-Related Central Blood Pressure Change Using Aortic Flow Triangulation

BACKGROUND

Pulsatile blood pressure rises with age, especially in the aorta. The comparative role of forward and reflected pressure waves (FW and RW, respectively), determined by aortic flow triangulation has not previously been explored in a large clinical cohort. This study aimed to identify the role of FW and RW in the rise in aortic pulse pressure with age.

METHODS

For 879 outpatients, aortic pressure waveforms were generated using a validated generalized transfer function applied to radial pressure waves recorded using applanation tonometry. FW and RW were subsequently determined using aortic flow triangulation. Contributions of FW and RW to rise in aortic pulse pressure with age were determined using multivariate linear regression and product of coefficient mediation analysis, with adjustment for height, weight, heart rate, and mean arterial pressure. Comparisons were made by gender and before and after age 60.

RESULTS

In subjects aged 60 and below, RW was an important contributor to pulsatile pressure elevation with age, but FW was non-contributory in either gender after multivariate correction. In subjects aged above 60, both FW and RW were significant and equal contributors in both genders.

CONCLUSIONS

In a clinical setting, both FW and RW are important to pulsatile aortic blood pressure across the lifespan, but RW appears to have a more pronounced effect across all ages, whereas FW has less effect in younger persons.