Forward Pressure Wave Research Articles

Association of Aortic Stiffness and Pressure Pulsatility With Noninvasive Estimates of Hepatic Steatosis and Fibrosis: The Framingham Heart Study.

Arterial stiffening may contribute to the pathogenesis of metabolic dysfunction-associated steatotic liver disease. We aimed to assess relations of vascular hemodynamic measures with measures of hepatic steatosis and fibrosis in the community. Our sample was drawn from the Framingham Offspring, New Offspring Spouse, Third Generation, Omni-1, and Omni-2 cohorts (N=3875; mean age, 56 years; 54% women). We used vibration-controlled transient elastography to assess controlled attenuation parameter and liver stiffness measurements as measures of liver steatosis and liver fibrosis, respectively. We assessed noninvasive vascular hemodynamics using arterial tonometry. We assessed cross-sectional relations of vascular hemodynamic measures with continuous and dichotomous measures of hepatic steatosis and fibrosis using multivariable linear and logistic regression. In multivariable models adjusting for cardiometabolic risk factors, higher carotid-femoral pulse wave velocity (estimated β per SD, 0.05 [95% CI, 0.01-0.09]; P=0.003), but not forward pressure wave amplitude and central pulse pressure, was associated with more liver steatosis (higher controlled attenuation parameter). Additionally, higher carotid-femoral pulse wave velocity (β=0.11 [95% CI, 0.07-0.15]; P<0.001), forward pressure wave amplitude (β=0.05 [95% CI, 0.01-0.09]; P=0.01), and central pulse pressure (β=0.05 [95% CI, 0.01-0.09]; P=0.01) were associated with more hepatic fibrosis (higher liver stiffness measurement). Associations were more prominent among men and among participants with obesity, diabetes, and metabolic syndrome (interaction P values, <0.001-0.04). Higher carotid-femoral pulse wave velocity, but not forward pressure wave amplitude and central pulse pressure, was associated with higher odds of hepatic steatosis (odds ratio, 1.16 [95% CI, 1.02-1.31]; P=0.02) and fibrosis (odds ratio, 1.40 [95% CI, 1.19-1.64]; P<0.001). Elevated aortic stiffness and pressure pulsatility may contribute to hepatic steatosis and fibrosis.

Association of Arterial Stiffness With Mid- to Long-Term Home Blood Pressure Variability in the Electronic Framingham Heart Study: Cohort Study.

Short-term blood pressure variability (BPV) is associated with arterial stiffness in patients with hypertension. Few studies have examined associations between arterial stiffness and digital home BPV over a mid- to long-term time span, irrespective of underlying hypertension. This study aims to investigate if arterial stiffness traits were associated with subsequent mid- to long-term home BPV in the electronic Framingham Heart Study (eFHS). We hypothesized that higher arterial stiffness was associated with higher home BPV over up to 1-year follow-up. At a Framingham Heart Study research examination (2016-2019), participants underwent arterial tonometry to acquire measures of arterial stiffness (carotid-femoral pulse wave velocity [CFPWV]; forward pressure wave amplitude [FWA]) and wave reflection (reflection coefficient [RC]). Participants who agreed to enroll in eFHS were provided with a digital blood pressure (BP) cuff to measure home BP weekly over up to 1-year follow-up. Participants with less than 3 weeks of BP readings were excluded. Linear regression models were used to examine associations of arterial measures with average real variability (ARV) of week-to-week home systolic (SBP) and diastolic (DBP) BP adjusting for important covariates. We obtained ARV as an average of the absolute differences of consecutive home BP measurements. ARV considers not only the dispersion of the BP readings around the mean but also the order of BP readings. In addition, ARV is more sensitive to measurement-to-measurement BPV compared with traditional BPV measures. Among 857 eFHS participants (mean age 54, SD 9 years; 508/857, 59% women; mean SBP/DBP 119/76 mm Hg; 405/857, 47% hypertension), 1 SD increment in FWA was associated with 0.16 (95% CI 0.09-0.23) SD increments in ARV of home SBP and 0.08 (95% CI 0.01-0.15) SD increments in ARV of home DBP; 1 SD increment in RC was associated with 0.14 (95% CI 0.07-0.22) SD increments in ARV of home SBP and 0.11 (95% CI 0.04-0.19) SD increments in ARV of home DBP. After adjusting for important covariates, there was no significant association between CFPWV and ARV of home SBP, and similarly, no significant association existed between CFPWV and ARV of home DBP (P>.05). In eFHS, higher FWA and RC were associated with higher mid- to long-term ARV of week-to-week home SBP and DBP over 1-year follow-up in individuals across the BP spectrum. Our findings suggest that higher aortic stiffness and wave reflection are associated with higher week-to-week variation of BP in a home-based setting over a mid- to long-term time span.

A sonic black hole of a rectangular cross-section

In this study, a rectangular cross-section sonic black hole (SBH) is explored and a one-dimensional model equation for the acoustic field inside it is presented. The model equation's applicability is verified through a comparison with the corresponding two-dimensional Helmholtz equation. A general analytical solution, which takes into account the SBH's quadratically varying internal cross-section, is derived using linearly independent confluent Heun functions. To investigate the acoustic wave behavior in the SBH, the wave splitting method is utilized to obtain forward and backward acoustic pressure waves, and the reflection coefficient is calculated. To confirm the validity of the analytical solution, a comparison is made with numerical results obtained from the Riccati equation. Within the context of this study, a detailed discussion is provided regarding the applicability of the analytical solution.

Relation of forward and backward traveling pressure waves with subclinical carotid artery wall remodeling and central pulse pressure.

Central pulse pressure (PP) is the sum of forward and backward traveling pressure waves that have been associated with cardiovascular disease (CVD) risk. However, previous studies have reported differential findings regarding the importance of the forward versus the backward wave for CVD risk. Therefore, we sought to determine the degree to which the forward and backward pressure waves are associated with subclinical carotid artery wall remodeling and central PP in healthy adults. Using applanation tonometry, carotid pressure waveforms were acquired in 308 healthy individuals (aged 45 ± 17 years, range 19-80 years, 61% women), from which the time integral of the forward (PfTI) and backward (PbTI) pressure waves were derived via pressure-only wave separation analysis. Common carotid artery intima-media thickness (cIMT), a biomarker of subclinical CVD risk, was derived via B-mode ultrasonography measured ∼2 cm from the carotid bulb. Both PfTI (r = 0.31, P < 0.001) and PbTI (r = 0.40, P < 0.001) were correlated with cIMT. However, further analysis revealed that PbTI mediated the relation between PfTI and cIMT (proportion mediated = 156%, P < 0.001). The association between PbTI and cIMT remained after adjusting for age, sex, body mass index, blood glucose, low-density lipoprotein cholesterol, heart rate, brachial systolic pressure, and aortic stiffness (B = 0.02, 95% confidence interval = 0.01, 2.77, P < 0.001). Both PfTI (r = -0.58, P < 0.001) and PbTI (r = -0.50, P < 0.001) were correlated with central PP, however, PfTI fully mediated the association between PbTI and central PP (proportion mediated = 124%, P < 0.001). Although PfTI is correlated with higher central PP, it is PbTI that is directly associated with carotid artery wall remodeling.NEW & NOTEWORTHY The present study contributes to the growing body of evidence highlighting the physiological and clinical insight provided by the pulsatile hemodynamic components of central artery pulse pressure. The notable findings of this study are: 1) The reflected (backward) pressure wave is associated with carotid intima-media thickness independent of traditional cardiovascular risk factors, including systolic blood pressure and aortic stiffness. 2) The incident (forward) pressure wave, and not the reflected pressure wave, is associated with greater central pulse pressure.

MARKED INCREASES IN PROXIMAL AORTIC CHARACTERISTIC IMPEDANCE AND HENCE FORWARD WAVE PRESSURES BEYOND BRACHIAL BLOOD PRESSURE IN ANGIOGRAPHIC PROVEN CORONARY ARTERY DISEASE

Objective: Although indexes of aortic stiffness increase the risk for coronary artery disease (CAD), the extent to which proximal aortic stiffness increases enhance central arterial forward wave pressures beyond changes in peripheral pressures, is uncertain. We aimed to determine whether increases in proximal aortic stiffness, as indexed by aortic characteristic impedance (Zc) translate into an enhanced central arterial pressure for a given brachial BP. Design and method: From central pressure, aortic velocity and outflow tract diameter measurements and echocardiography, we determined Zc and arterial pressure wave morphology in 71 patients with angiographic proven CAD and all other cardiac pathology excluded. We compared central arterial function in these patients with 230 age and sex-matched controls from a community study, and in patients with stroke and CLI (n = 287) diagnosed in a hospital setting. Results: Adjusting for confounders, including mean arterial pressure, and aortic root diameter, as compared to controls, both Zc and the pressures generated by the product of peak aortic flow (Q) and Zc (PQxZc) were markedly increased in patients with CAD (p&lt;0.0001) and those with stroke or CLI (p&lt;0.005). Moreover, compared to patients with stroke and CLI, those with CAD also had marked increases in both Zc and PQxZc (p&lt;0.0001). Consequently, with adjustments for the same confounders, pressures generated by forward wave pressures (Pf) were markedly increased in patients with CAD as compared to controls and to patients with alternative arterial diseases (p&lt;0.0001). Importantly, after further adjustments for brachial PP or SBP, the higher Pf values in patients with CAD were retained (p&lt;0.005 to &lt;0.0001). However, with adjustments for brachial SBP and confounders, central aortic PP did not differ between groups. Conclusions: Independent of confounders and aortic root diameter, a marked increase in proximal aortic Zc occurs in patients with CAD as compared to both controls and patients with arterial disease in alternative beds. This translates into a greater central arterial pulsatile load determined by forward travelling pressure waves, but not peak central PP than that predicted by brachial BP measurements. These data support a need for intense brachial BP lowering in CAD.

SEX DIFFERENCES IN PULSE WAVE AND SUBENDOCARDIAL VIABILITY RATIO IN HYPERTENSIVE PATIENTS

Objective: Myocardial ischemia represents the main cause of morbidity and mortality in hypertensive patients in both women and men, although some difference in pathophysiology and in the exposure to risk factors may explain the lower global cardiovascular risk of women. Sex differences in the structure and function of the cardiovascular system may affect the aortic pressure wave and the functional balance in myocardial perfusion determined by central aortic pressure, which may lead to myocardial ischemia and type 2 myocardial infarction. Design and method: In a population of 318 treated hypertensive patients (162 females, 156 males) referring to a single Hypertension centre (University of Trieste, Italy), we measured peripheral blood pressure and performed arterial applanation tonometry (PulsePen, DiaTecne, Italy) to determine central blood pressure waveform, aortic pulse wave velocity (PWV), augmentation index (AIx), pulse wave separation analysis with timing and amplitude of forward (fT, fP) and backward reflected (bT, bP) waves, and the subendocardial viability ratio (SEVR), i.e. the ratio between diastolic and systolic pressure-time index, as a risk marker of myocardial ischemia. Results: Despite similar peripheral systolic and diastolic blood pressure values, heart rate and PWV between sexes, females showed a longer forward pressure wave duration (119.8±38.6 vs 105.0±30.4 ms, p&lt;0.0001) and lower amplitude (52.7±19,4 vs 57.1±19.3 mmHg, p = 0.039) compared to males. Backward pressure waved were similar in timing and amplitude between males and females. The difference in forward wave caused a marked higher AIx (19.5±12.4 vs 11.9±14.9, p&lt;0.0001) and a lower SEVR (101.6±24.4 vs 108.5±27.7, p = 0.018) in women compared to men. Conclusions: Hypertensive women and men showed significant differences in forward pressure wave, causing a significant increase in AIx and a decreased SEVR in women compared to men. This may have important implications in sex-specific risk and myocardial ischemia.

Wave reflection quantification analysis and personalized flow wave estimation based on the central aortic pressure waveform.

Pulse wave reflections reflect cardiac afterload and perfusion, which yield valid indicators for monitoring cardiovascular status. Accurate quantification of pressure wave reflections requires the measurement of aortic flow wave. However, direct flow measurement involves extra equipment and well-trained operator. In this study, the personalized aortic flow waveform was estimated from the individual central aortic pressure waveform (CAPW) based on pressure-flow relations. The separated forward and backward pressure waves were used to calculate wave reflection indices such as reflection index (RI) and reflection magnitude (RM), as well as the central aortic pulse transit time (PTT). The effectiveness and feasibility of the method were validated by a set of clinical data (13 participants) and the Nektar1D Pulse Wave Database (4,374 subjects). The performance of the proposed personalized flow waveform method was compared with the traditional triangular flow waveform method and the recently proposed lognormal flow waveform method by statistical analyses. Results show that the root mean square error calculated by the personalized flow waveform approach is smaller than that of the typical triangular and lognormal flow methods, and the correlation coefficient with the measured flow waveform is higher. The estimated personalized flow waveform based on the characteristics of the CAPW can estimate wave reflection indices more accurately than the other two methods. The proposed personalized flow waveform method can be potentially used as a convenient alternative for the measurement of aortic flow waveform.

Abstract 14300: Arterial Stiffness is Associated With Intermediate-Term Home Blood Pressure Variability: The Electronic Framingham Heart Study

Introduction: Short-term blood pressure variability (BPV) is associated with arterial stiffness in patients with hypertension. Few studies examined associations between arterial stiffness and digital home BPV over an intermediate time span. Objective: We investigated if antecedent arterial stiffness was associated with home BPV among participants in the electronic Framingham Heart Study (eFHS). We hypothesize that higher arterial stiffness predicts higher intermediate-term home BPV over one-year follow-up. Methods: At an FHS research exam (2016-2019), participants underwent arterial tonometry to acquire mean arterial pressure (MAP) and measures of arterial stiffness (carotid femoral pulse wave velocity, CFPWV; forward pressure wave amplitude, FWA) and wave reflection (reflection coefficient, RC). Participants who agreed to enroll in eFHS were provided with a digital blood pressure (BP) cuff to measure home BP weekly. Participants with &lt; 3 weeks of BP readings were excluded. Linear regression models were used to examine associations of arterial measures with home average real variability (ARV) of systolic (SBP) and diastolic (DBP) BP adjusting for covariates. We obtained ARV as an average of the absolute differences of consecutive BP measurements. ARV considers not only the dispersion of the BP readings around the mean, but also the order of BP readings. We used p&lt;0.05 for significance. Results: Among 857 eFHS participants (mean age 54 years, 59% women, mean BP 119/76, 47% hypertension, mean ARV of DBP 5.50, mean ARV of SBP 8.61), higher FWA and RC were associated with higher ARV of SBP ( Table ). Higher CFPWV was associated with lower ARV of DBP ( Table ). Conclusion: In eFHS, higher FWA and RC were associated with higher intermediate-term home BPV of SBP while higher CFPWV was associated with blunted BPV of DBP. Our findings suggest that higher aortic stiffness and wave reflection may affect day-to-day modulation of blood pressure in a home-based setting.

Menopause influences aortic pulse pressure and pressure wave responses to metaboreflex activation in women.

Postmenopausal women (post-MW) have greater risk of heart failure due to aortic pulsatile overload on the left ventricle associated with increased backward wave pressure (Pb). Post-MW have exaggerated peripheral blood pressure (BP) response to exercise mediated by metaboreflex (postexercise muscle ischemia [PEMI]) overactivation. Increased forward wave pressure (Pf) and Pb are determinants of aortic pulse pressure (PP) during isometric handgrip exercis (IHG) in young adults. We hypothesized that aortic PP and pressure wave responses to PEMI are augmented in nonhypertensive post-MW compared with premenopausal women (pre-MW). Aortic BP, Pf, Pb, and reflection magnitude were assessed at rest and during IHG and PEMI by applanation tonometry in 15 pre-MW and 16 post-MW. Aortic systolic BP during PEMI similarly increased in both groups. The increase in diastolic BP was lower in post-MW (post-MW Δ6 ± 2 vs pre-MW Δ11 ± 2 mm Hg, P < 0.05). Aortic PP (post-MW Δ8 ± 2 vs pre-MW Δ3 ± 2), Pf (post-MW Δ6 ± 1 vs pre-MW Δ0 ± 1), and Pb (post-MW Δ5 ± 1 vs pre-MW Δ2 ± 1) augmented during PEMI in post-MW ( P < 0.05 for all), but not in pre-MW. Reflection magnitude increased during PEMI only in pre-MW (pre-MW Δ7 ± 2 vs post-MW Δ-1 ± 2, P < 0.05) due to concurrent increases in Pf and Pb in post-MW. Even in nonhypertensive postmenopausal women, increases in Pf and Pb and decrease in aortic DBP are important factors that contribute to the augmented aortic PP response to PEMI.

Contribution of Increases in Late Systolic Ejection Volume to the Impact of Heart Rate on Central Arterial Pulse Pressure in a Community Sample.

A lower heart rate (HR) increases left ventricular (LV) ejection volume. Whether this contributes to the adverse effects of HR on central pulse pressure (PPc) through reservoir volume effects is uncertain. Using noninvasive central pressure, aortic velocity, and diameter measurements in the outflow tract (echocardiography), we assessed the role of LV ejection volume as a determinant of HR relations with PPc in 824 community participants. A lower HR was independently associated with both stroke volume (SV) (P < 0.001) and a shift in ejection volume from early (until the first systolic shoulder) to late (from first systolic shoulder to peak PP) systole (P < 0.05 to P < 0.005). Adjustments for LV end diastolic volume markedly diminished HR relations with SV and indexes of the shift in ejection volume to late systole. A lower HR was also independently associated with increases in forward traveling pressure waves (Pf) and PPc (P < 0.0001). However, adjustments for neither SV, nor indexes of a shift in ejection volume to late systole modified HR-Pf or PPc relations. This was despite relationships between indexes of a shift in ejection volume to late systole and both Pf and PPc (P < 0.0001). In contrast, adjustments for the increases in re-reflected and backward traveling wave pressures with a lower HR, eliminated HR-Pf and PPc relations. In contrast to current thought, a lower HR is not associated with increases in PPc through an impact of increases in late systolic ejection volume on aortic reservoir volume, but rather through increases in backward wave pressures.

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 MULTI-ETHNIC COHORT: THE HELIUS STUDY

Objective: The reflection magnitude (RM), the ratio of the amplitudes of the backward and forward central arterial pressure waves, has been shown to be predictive for future cardiovascular events, but the association between blood pressure (BP) and RM remains unknown. We aimed to assess the association between RM, BP and hypertension in a large multi-ethnic population-based cohort study. Design and method: We assessed RM in 10 195 individuals of Dutch, South-Asian Surinamese, African Surinamese, Ghanaian, Turkish and Moroccan origin aged between 18–70 years (54.2% female) participating in the HEalthy Life in an Urban Setting (HELIUS) study. To determine RM, central arterial pressure and flow were reconstructed from non-invasive finger BP measurements using a generalized transfer function and Windkessel model, whereafter wave separation was performed (Fig 1, panel A &amp; B). Hypertension was defined based on office-BP and use of BP lowering medication. Associations between RM and systolic- and diastolic BP, hypertension, and hypertension mediated end-organ damage were assessed using regression models with correction for age, height, ethnicity and an interaction term for sex. Results: Mean RM was 62.5% (SD 8.0) in men and 63.8% (SD 8.1) in women. For every 10 mmHg increase in systolic BP, RM increased linearly by 1.35 (95% CI 1.23–1.46) from 120 mmHg onwards, while for every 10 mmHg increase in diastolic BP above 80 mmHg RM increased by 1.99 (95% CI 1.61 – 2.38) (Fig 1, panel C &amp; D). 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. RM was 1.64 (95% CI 1.09–2.20) and 0.94 (95% CI 0.37–1.52) higher in hypertensive men and women with ECG-based left ventricular hypertrophy or increased albuminuria compared to hypertensive men and women without hypertensive organ damage. Following correction for height ethnic and sex differences in RM were attenuated, however the relation with BP did not change. Conclusions: Hypertension is associated with a higher RM in men and women of different ethnic origins, and may, in part, explain disparities in hypertension associated cardiovascular risk.

Carotid Reservoir Pressure Decrease After Prolonged Head Down Tilt Bed Rest in Young Healthy Subjects Is Associated With Reduction in Left Ventricular Ejection Time and Diastolic Length.

BackgroundThe arterial pressure waveform reflects the interaction between the heart and the arterial system and carries potentially relevant information about circulatory status. According to the commonly accepted ‘wave transmission model’, the net BP waveform results from the super-position of discrete forward and backward pressure waves, with the forward wave in systole determined mainly by the left ventricular (LV) ejection function and the backward by the wave reflection from the periphery, the timing and amplitude of which depend on arterial stiffness, the wave propagation speed and the extent of downstream admittance mismatching. However, this approach obscures the ‘Windkessel function’ of the elastic arteries. Recently, a ‘reservoir-excess pressure’ model has been proposed, which interprets the arterial BP waveform as a composite of a volume-related ‘reservoir’ pressure and a wave-related ‘excess’ pressure.MethodsIn this study we applied the reservoir-excess pressure approach to the analysis of carotid arterial pressure waveforms (applanation tonometry) in 10 young healthy volunteers before and after a 5-week head down tilt bed rest which induced a significant reduction in stroke volume (SV), end-diastolic LV volume and LV longitudinal function without significant changes in central blood pressure, cardiac output, total peripheral resistance and aortic stiffness. Forward and backward pressure components were also determined by wave separation analysis.ResultsCompared to the baseline state, bed rest induced a significant reduction in LV ejection time (LVET), diastolic time (DT), backward pressure amplitude (bP) and pressure reservoir integral (INTPR). INTPR correlated directly with LVET, DT, time to the peak of backward wave (bT) and stroke volume, while excess pressure integral (INTXSP) correlated directly with central pressure. Furthermore, Δ.INTPR correlated directly with Δ.LVET, and Δ.DT, and in multivariate analysis INTPR was independently related to LVET and DT and INTXSP to central systolic BP.ConclusionThis is an hypothesis generating paper which adds support to the idea that the reservoir-wave hypothesis applied to non-invasively obtained carotid pressure waveforms is of potential clinical usefulness.

Single vs Serial Assessments of Arterial Hemodynamics to Predict Thoracic Aortic Aneurysm Expansion

BackgroundThoracic aortic aneurysm (TAA) is a highly morbid disease. We have previously shown that baseline hemodynamic measures reflecting aortic function are associated with future TAA expansion. However, whether serial arterial hemodynamic assessment further improves TAA growth assessment remains unknown. Therefore, we aimed to compare single vs serial arterial hemodynamic assessments in the evaluation of future TAA growth. MethodsEighty-six unoperated participants with TAA underwent noninvasive arterial hemodynamic assessment using arterial tonometry and echocardiography at baseline and after 1 year. Aortic diameter was measured serially with the use of standard imaging modalities. Stepwise multivariable linear regression was used to assess associations of baseline and 1-year change (Δ) in arterial hemodynamic measures with TAA growth. ResultsMean age was 62.7 ± 11.0 years; 79% were male. Mean aneurysm growth was 0.48 ± 0.54 mm/year after a follow-up of 2.96 ± 1.03 years. Yearly changes in arterial hemodynamic measures ranged from −3.2% to +4.2%. Linear regression results showed that while baseline arterial hemodynamic measures were independently associated with aneurysm growth (carotid-femoral pulse wave velocity: β ± SE = 0.038 ± 0.013; aortic characteristic impedance: β ± SE = 0.002 ± 0.001; proximal aortic compliance: β ± SE = −0.011 ± 0.006; forward pressure wave amplitude: β ± SE 0.009 ± 0.002; reflected pressure wave amplitude: β ± SE = 0.017 ± 0.006; P < 0.05 for each), the 1-year Δ in these measures did not incrementally add to aneurysm growth assessment (P > 0.05 for each Δ). ConclusionsAlthough baseline measures of aortic function independently predict TAA expansion, 1-year changes in these measures do not improve this prediction. Thus, for TAA risk assessment purposes, a baseline assessment of aortic function may suffice, which simplifies its use for potential predictive algorithms.

The effect of left ventricular contractility on arterial hemodynamics: A model-based investigation.

Ventricular-arterial coupling is a major determinant of cardiovascular performance, however, there are still inherent difficulties in distinguishing ventricular from vascular effects on arterial pulse phenotypes. In the present study, we employed an extensive mathematical model of the cardiovascular system to investigate how sole changes in cardiac contractility might affect hemodynamics. We simulated two physiologically relevant cases of high and low contractility by altering the end-systolic elastance, Ees, (3 versus 1 mmHg/mL) under constant cardiac output and afterload, and subsequently performed pulse wave analysis and wave separation. The aortic forward pressure wave component was steeper for high Ees, which led to the change of the total pressure waveform from the characteristic Type A phenotype to Type C, and the decrease in augmentation index, AIx (-2.4% versus +18.1%). Additionally, the increase in Ees caused the pulse pressure amplification from the aorta to the radial artery to rise drastically (1.86 versus 1.39). Our results show that an increase in cardiac contractility alone, with no concomitant change in arterial properties, alters the shape of the forward pressure wave, which, consequently, changes central and peripheral pulse phenotypes. Indices based on the pressure waveform, like AIx, cannot be assumed to reflect only arterial properties.

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

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. 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 ± 17ms; light, 144 ± 15ms; moderate, 129 ± 16ms; vigorous, 121 ± 17ms). 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.

Pulsatile load and wasted pressure effort are reduced following an acute bout of aerobic exercise.

Following aerobic exercise, sustained vasodilation and concomitant reductions in total peripheral resistance (TPR) result in a reduction in blood pressure that is maintained for two or more hours. However, the time course for postexercise changes in reflected wave amplitude and other indices of pulsatile load on the left ventricle have not been thoroughly described. Therefore, we tested the hypothesis that reflected wave amplitude is reduced beyond an hour after cycling at 60% V̇o2peak for 60 min. Aortic pressure waveforms were derived in 14 healthy adults (7 men, 7 women; 26 ± 3 yr) from radial pulse waves acquired via high-fidelity applanation tonometry at baseline and every 20 min for 120 min postexercise. Concurrently, left ventricle outflow velocities were acquired via Doppler echocardiography and pressure-flow analyses were performed. Aortic characteristic impedance (Zc), forward (Pf) and backward (Pb) pulse wave amplitude, reflected wave travel time (RWTT), and wasted pressure effort (WPE) were derived. Reductions in aortic blood pressure, Zc, Pf, and Pb were all sustained postexercise whereas increases in RWTT emerged from 60 to 100 min post exercise (all P < 0.05). WPE was reduced by ∼40% from 40 to 100 min post exercise (all P < 0.02). Stepwise multiple regression analysis revealed that the peak ΔWPE was associated with ΔRWTT (β = -0.57, P = 0.003) and ΔPb (β = 0.52, P = 0.006), but not Δcardiac output, ΔTPR, ΔZc, or ΔPf. These results suggest that changes in pulsatile hemodynamics are sustained for ≥100 min following moderate intensity aerobic exercise. Moreover, decreased and delayed reflected pressure waves are associated with decreased left ventricular wasted effort after exercise.NEW & NOTEWORTHY We demonstrate that pulsatile load on the left ventricle is diminished following 60 min of moderate intensity aerobic exercise. During recovery from exercise, the amplitude of the forward and backward traveling pressure waves are attenuated and the arrival of reflected waves is delayed. Thus, the work imposed upon the left ventricle by reflected pressure waves, wasted pressure effort, is decreased after exercise.

PARALLEL CHANGE IN PERIPHERAL AND NONAUGMENTED CENTRAL PULSE PRESSURE WITH AGE

Objective: Peripheral pulse pressure (PP) decreases in parallel to stroke volume during young adulthood, reaching a nadir in midlife. We postulate that during the same period, the progressive augmentation produced by wave reflection could overcome the effect of a decrease in forward pressure wave on central PP. The aim of the study was to evaluate the contribution of forward and backward pressure waves to the age related change in central PP and its expression at the brachial level. Design and method: This is a cross-sectional analysis of a cohort of 212 unmedicated hypertensive patients (16–93 years). Central PP (applanation tonometry of the radial pulse) and carotid-femoral pulse wave velocity (PWV) were assessed with a SphygmoCor device (operator index &gt;70%). Central pressure waveform was calibrated with brachial SBP and DBP (OMRON 705). Augmentation pressure (AP) was calculated as the difference between the second and first systolic peaks. Forward pressure wave (nonaugmented central PP) was calculated as central PP - AP. Age was stratified in 3 groups: &lt;30, 31–60 and &gt;60 years. Comparisons were tested by ANOVA. Results: Peripheral PP showed two peaks, one before age 30 and another after age 60, with a nadir between 31–60 years (59 ± 15, 48 ± 10 mmHg and 58 ± 12 mmHg; in &lt; 30, 31–60 and &gt;60 years respectively; ANOVA &lt;0.001). Forward pressure wave changed in parallel to peripheral PP, describing two peaks, one before 30 years and one after 60 years, and a nadir at 41–50 years (33 ± 8, 27 ± 6 and 32 ± 7 mmHg; in&lt;30, 31–60 and &gt;60 years respectively; ANOVA &lt;0.001). In contrast, AP increased steadily with age (0.2 ± 5, 8 ± 6 and 15 ± 6 mmHg; in &lt;30, 31–60 and &gt;60 years respectively; ANOVA &lt;0.001), in parallel to PWV (6.2 ± 1, 7.1 ± 1 and 8.7 ± 1.5 m/s, respectively; &lt;0.001). As a result (figure), augmented central PP remained constant before increasing after age 60 (35 ± 7, 35 ± 8 and 47 ± 11 mmHg; at &lt;30, 31–60 and &gt;60 years respectively; ANOVA &lt;0.001). Conclusions: Peripheral and nonaugmented central PP exhibited a parallel U shape relationship with age. The progressive increase in AP masked the nadir in forward pressure wave and minimized peripheral amplification.

FORWARD WAVE AND ITS IMPACT ON AUGMENTATION INDEX: DO GENDER DIFFERENCES EXIST?

Objective: Some studies have found that women have markedly higher aortic augmentation index (Aix) than men. Traditionally, this difference has been attributed to the early return of the reflected wave because of shorter stature and increased aortic stiffness in women. However, augmentation pressure is also affected by the shape of the forward wave. We aimed to assess the impact of gender on the association between forward aortic wave time, pressure and Aix in hypertensive patients. Design and method: 30 men and 37 women with hypertension were enrolled. Central hemodynamic was assessed using applanation tonometry method (SphygmoCor-Australia). We estimated central systolic and diastolic pressure, Aix, Aix adjusted by heart rate (Aix@75), pulse wave velocity (PWV), forward wave pressure (FWP), ejection duration (ED), time to peak forward wave (T1), time to peak systolic wave (T2) and reflected wave foot time (Tr). Results: Men and women had similar median of age (64 vs 66, p = 0.34), heart rate (77 vs 78, p = 0.40), peripheral systolic (133 vs 130mmHg, p = 0.32) and diastolic (80 vs 77mmHg, p = 0.16) pressure. Despite similar central systolic (119 vs 117mmHg, p = 0.47), diastolic (81 vs 78mmHg, p = 0.19) pressure and PWV (9.9 vs 9.4m/s, p = 0.79), women had higher Aix (33 vs 23%, p &lt; 0.001), and Aix@75 (34 vs 26%; p &lt; 0.001). Men and women had similar T2 and FWP, but Tr was higher in men (134 vs 130ms; p = 0.04), whereas ED (301 vs 314ms) and T1 (105 vs 109ms) – in women (p &lt; 0.05). Tr minus T1 was higher in men (30 vs 22ms; p = 0.014). In a multivariate regression analysis in men Aix@75 was significantly associated with PWV (beta = 0.75, p = 0.005), whereas in women – with T1 (beta = 0.32, p = 0.04) and Tr (beta = 0.42, p = 0.009). Conclusions: As according to previous reports, women had higher Aix and Aix@75 and shorter time to backward wave return. However, we also found that men and women had different ejection patterns and women had higher forward wave peak time, that was significantly related to Aix@75 only in them. It may indicate that shape and time of the forward wave may also contribute to higher Aix in women compared to men.

Impact of pulmonary wave reflection in heart failure: right ventricular-arterial coupling

Abstract Background Pulmonary wave reflection, an important loading component on RV, would help better describe right ventricular (RV) – arterial uncouplingin type II pulmonary hypertension (PH). Methods This study included 105patients with type II PH (age = 72±13 years old, ejection fraction = 47±21%). Pulmonary wave reflection was characterised by estimating pressure and velocity profiles from Doppler measurement and separating pressure waveform into forward (Pf) and backward pressure (Pb) waves based on the concept of wave intensity. The relationship of RV strain against Pb or pulmonary artery systolic pressure (PASP) was compared between patients with and without subsequent event of worsening heart failure, using discriminant analysis. Results Sample profiles of pressure waveforms illustrated Pb accounted for a significant proportion of total pressure (figure A). When RV strain was plotted against Pb, the distribution of both group were clearly separated, indicating significant uncoupling in patients with events, whereas when plotted against PASP, the both groups were overlapped (figure B and C). Conclusions Pulmonary wave reflection can better describe RV-arterial uncoupling in type II PH. Funding Acknowledgement Type of funding source: None