Repeated reflection of waves in the systemic arterial system

1993 ◽  
Vol 264 (1) ◽  
pp. H269-H281 ◽  
Author(s):  
D. S. Berger ◽  
J. K. Li ◽  
W. K. Laskey ◽  
A. Noordergraaf
Keyword(s):  
Wave Reflection ◽  
Aortic Pressure ◽  
Arterial System ◽  
Tube Length ◽  
Pharmacological Intervention ◽  
Forward Wave ◽  
Heart Tube ◽  
Complex Load ◽  
Backward Wave ◽  
Reflection Theory

Traditional analysis of pulse-wave propagation and reflection in the arterial system treats measured pressure and flow waves as the sum of a single forward wave (traveling away from the heart) and a single backward wave (traveling toward the heart). The purpose of this study was to develop a more general wave reflection theory that allows repeated reflection of these waves. The arterial system was modeled as a uniform viscoelastic tube terminating in a complex load with reflections occurring at the tube load interface and the heart tube interface. The resulting framework considers the forward wave to be the sum of an initial wave plus a series of antegrade waves. Similarly, the backward wave is the sum of a series of retrograde waves. This repeated reflection theory contains within it the traditional forward/backward wave reflection analysis as a special case. In addition, the individual antegrade and retrograde waves, at the tube entrance, are shown to be independent of the tube length. Aortic pressure and flow data, from dog experiments, were used to illustrate the phenomenon of repeated reflections. Alteration of the arterial system loading conditions, brought about through pharmacological intervention, affected the number and morphology of repeated waves. These results are compared with those found in traditional forward/backward reflection analysis.

Empirical estimates of mean aortic pressure: advantages, drawbacks and implications for pressure redundancy

2002 ◽  
Vol 103 (1) ◽  
pp. 7-13 ◽  
Author(s):  
Denis CHEMLA ◽  
Jean-Louis HÉBERT ◽  
Eduardo APTECAR ◽  
Jean-Xavier MAZOIT ◽  
Karen ZAMANI ◽  
...  
Keyword(s):  
Form Factor ◽  
Pulse Pressure ◽  
Wave Reflection ◽  
Diastolic Pressure ◽  
Augmentation Index ◽  
Aortic Pressure ◽  
Arterial System ◽  
Wave Amplification ◽  
Empirical Estimates ◽  
Alternative Formula

Mean arterial pressure (MAP) is estimated at the brachial artery level by adding a fraction of pulse pressure (form factor; = 0.33) to diastolic pressure. We tested the hypothesis that a fixed form factor can also be used at the aortic root level. We recorded systolic aortic pressure (SAP) and diastolic aortic pressure (DAP), and we calculated aortic pulse pressure (PP) and the time-averaged MAP in the aorta of resting adults (n = 73; age 43±14 years). Wave reflection was quantified using the augmentation index. The aortic form factor (range 0.35-0.53) decreased with age, MAP, PP and augmentation index (each P<0.001). The mean form factor value (0.45) gave a reasonable estimation of MAP (MAP = DAP+0.45PP; bias = 0±2mmHg), and the bias increased with MAP (P<0.001). An alternative formula (MAP = DAP+PP/3+5mmHg) gave a more precise estimation (bias = 0±1mmHg), and the bias was not related to MAP. This latter formula was consistent with the previously reported mean pulse wave amplification of 15mmHg, and with unchanged MAP and diastolic pressure from aorta to periphery. Multiple linear regression showed that 99% of the variability of MAP was explained by the combined influence of DAP and SAP, thus confirming major pressure redundancy. Results were obtained irrespective of whether the marked differences in heart period and extent of wave reflection between subjects were taken into account. In conclusion, the aortic form factor was strongly influenced by age, aortic pressure and wave reflection. An empirical formula (MAP = DAP+PP/3+5mmHg) that is consistent with mechanical principles in the arterial system gave a more precise estimate of MAP in the aorta of resting humans. Only two distinct pressure-powered functions were carried out in the (SAP, DAP, MAP, PP) four-pressure set.

scholarly journals The arterial reservoir pressure increases with aging and is the major determinant of the aortic augmentation index

2010 ◽  
Vol 298 (2) ◽  
pp. H580-H586 ◽  
Author(s):  
Justin E. Davies ◽  
John Baksi ◽  
Darrel P. Francis ◽  
Nearchos Hadjiloizou ◽  
Zachary I. Whinnett ◽  
...  
Keyword(s):  
Wave Reflection ◽  
Peak Pressure ◽  
Augmentation Index ◽  
Doppler Velocity ◽  
Reservoir Pressure ◽  
Forward Wave ◽  
Reservoir Function ◽  
Augmentation Pressure ◽  
Age Related ◽  
Backward Wave

The augmentation index predicts cardiovascular mortality and is usually explained as a distally reflected wave adding to the forward wave generated by systole. We propose that the capacitative properties of the aorta (the arterial reservoir) also contribute significantly to the augmentation index and have calculated the contribution of the arterial reservoir, independently of wave reflection, and assessed how these contributions change with aging. In 15 subjects (aged 53 ± 10 yr), we measured pressure and Doppler velocity simultaneously in the proximal aorta using intra-arterial wires. We calculated the components of augmentation pressure in two ways: 1) into forward and backward (reflected) components by established separation methods, and 2) using an approach that accounts for an additional reservoir component. When the reservoir was ignored, augmentation pressure (22.7 ± 13.9 mmHg) comprised a small forward wave (peak pressure = 6.5 ± 9.4 mmHg) and a larger backward wave (peak pressure = 16.2 ± 7.6 mmHg). After we took account of the reservoir, the contribution to augmentation pressure of the backward wave was reduced by 64% to 5.8 ± 4.4 mmHg ( P < 0.001), forward pressure was negligible, and reservoir pressure was the largest component (peak pressure = 19.8 ± 9.3 mmHg). With age, reservoir pressure increased progressively (9.9 mmHg/decade, r = 0.69, P < 0.001). In conclusion, the augmentation index is principally determined by aortic reservoir function and other elastic arteries and only to a minor extent by reflected waves. Reservoir function rather than wave reflection changes markedly with aging, which accounts for the age-related changes in the aortic pressure waveform.

Effects of Diabetes and Gender on Mechanical Properties of the Arterial System in Rats: Aortic Impedance Analysis1

2003 ◽  
Vol 228 (1) ◽  
pp. 70-78 ◽  
Author(s):  
Kuo-Chu Chang ◽  
Kwan-Lih Hsu ◽  
Yung-Zu Tseng
Keyword(s):  
Transit Time ◽  
Input Impedance ◽  
Wave Reflection ◽  
Characteristic Impedance ◽  
Aortic Distensibility ◽  
Aortic Pressure ◽  
Diabetic Rats ◽  
Arterial System ◽  
Reflection Factor ◽  
Aortic Input Impedance

We determined the effects of diabetes and gender on the physical properties of the vasculature in streptozotocin (STZ)-treated rats based on the aortic input impedance analysis. Rats given STZ 65 mg/kg i.v. were compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured and were then subjected to Fourier transformation for the analysis of aortic input impedance. Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra. Male but not female diabetic rats exhibited an increase in cardiac output in the absence of any significant changes in arterial blood pressure, resulting in a decline in total peripheral resistance. However, in each gender group, diabetes contributed to an increase in wave reflection factor, from 0.47 ± 0.04 to 0.84 ± 0.03 in males and from 0.46 ± 0.03 to 0.81 ± 0.03 in females. Diabetic rats had reduced wave transit time, at 18.82 ± 0.60 vs 21.34 ± 0.51 msec in males and at 19.63 ± 0.37 vs 22.74 ± 0.57 msec in females. Changes in wave transit time and reflection factor indicate that diabetes can modify the timing and magnitude of the wave reflection in the rat arterial system. Meanwhile, diabetes produced a fall in aortic characteristic impedance from 0.023 ± 0.002 to 0.009 ± 0.001 mmHg/min/kg/ml in males and from 0.028 ± 0.002 to 0.014 ± 0.001 mmHg/min/kg/ml in females. With unaltered aortic pressure, both the diminished aortic characteristic impedance and wave transit time suggest that the muscle inactivation in diabetes may occur in aortas and large arteries and may cause a detriment to the aortic distensibility in rats with either sex. We conclude that only rats with male gender diabetes produce a detriment to the physical properties of the resistance arterioles. In spite of male or female gender, diabetes decreases the aortic distensibility and impairs the wave reflection phenomenon in the rat arterial system.

Wave reflection augments central systolic and pulse pressures during facial cooling

2008 ◽  
Vol 294 (6) ◽  
pp. H2535-H2539 ◽  
Author(s):  
David G. Edwards ◽  
Matthew S. Roy ◽  
Raju Y. Prasad
Keyword(s):  
Cardiovascular Events ◽  
Wave Reflection ◽  
Augmentation Index ◽  
Systolic Pressure ◽  
Aortic Pressure ◽  
Applanation Tonometry ◽  
Pressure Waveform ◽  
Central Aortic Pressure ◽  
Facial Cooling ◽  
Change In Mean

Cardiovascular events are more common in the winter months, possibly because of hemodynamic alterations in response to cold exposure. The purpose of this study was to determine the effect of acute facial cooling on central aortic pressure, arterial stiffness, and wave reflection. Twelve healthy subjects (age 23 ± 3 yr; 6 men, 6 women) underwent supine measurements of carotid-femoral pulse wave velocity (PWV), brachial artery blood pressure, and central aortic pressure (via the synthesis of a central aortic pressure waveform by radial artery applanation tonometry and generalized transfer function) during a control trial (supine rest) and a facial cooling trial (0°C gel pack). Aortic augmentation index (AI), an index of wave reflection, was calculated from the aortic pressure waveform. Measurements were made at baseline, 2 min, and 7 min during each trial. Facial cooling increased ( P < 0.05) peripheral and central diastolic and systolic pressures. Central systolic pressure increased more than peripheral systolic pressure (22 ± 3 vs. 15 ± 2 mmHg; P < 0.05), resulting in decreased pulse pressure amplification ratio. Facial cooling resulted in a robust increase in AI and a modest increase in PWV (AI: −1.4 ± 3.8 vs. 21.2 ± 3.0 and 19.9 ± 3.6%; PWV: 5.6 ± 0.2 vs. 6.5 ± 0.3 and 6.2 ± 0.2 m/s; P < 0.05). Change in mean arterial pressure but not PWV predicted the change in AI, suggesting that facial cooling may increase AI independent of aortic PWV. Facial cooling and the resulting peripheral vasoconstriction are associated with an increase in wave reflection and augmentation of central systolic pressure, potentially explaining ischemia and cardiovascular events in the cold.

scholarly journals Effects of aerobic, resistance and concurrent exercise on pulse wave reflection and autonomic modulation in men with elevated blood pressure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paulo Farinatti ◽  
Alex da Silva Itaborahy ◽  
Tainah de Paula ◽  
Walace David Monteiro ◽  
Mário F. Neves
Keyword(s):  
Blood Pressure ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Augmentation Index ◽  
Aortic Pressure ◽  
Elevated Blood Pressure ◽  
Autonomic Modulation ◽  
Elevated Blood ◽  
Pulse Wave Reflection ◽  
Concurrent Exercise

AbstractThe acute effects of exercise modes on pulse wave reflection (PWR) and their relationship with autonomic control remain undefined, particularly in individuals with elevated blood pressure (BP). We compared PWR and autonomic modulation after acute aerobic (AE), resistance (RE), and concurrent exercise (CE) in 15 men with stage-1 hypertension (mean ± SE: 34.7 ± 2.5 years, 28.4 ± 0.6 kg/m2, 133 ± 1/82 ± 2 mmHg). Participants underwent AE, RE, and CE on different days in counterbalanced order. Applanation tonometry and heart rate variability assessments were performed before and 30-min postexercise. Aortic pressure decreased after AE (− 2.4 ± 0.7 mmHg; P = 0.01), RE (− 2.2 ± 0.6 mmHg; P = 0.03), and CE (− 3.1 ± 0.5 mmHg; P = 0.003). Augmentation index remained stable after RE, but lowered after AE (− 5.1 ± 1.7%; P = 0.03) and CE (− 7.6 ± 2.4% P = 0.002). Systolic BP reduction occurred after CE (− 5.3 ± 1.9 mmHg). RR-intervals and parasympathetic modulation lowered after all conditions (~ 30–40%; P < 0.05), while the sympathovagal balance increased after RE (1.2 ± 0.3–1.3 ± 0.3 n.u., P < 0.05). Changes in PWR correlated inversely with sympathetic and directly with vagal modulation in CE. In conclusion, AE, RE, and CE lowered central aortic pressure, but only AE and CE reduced PWR. Overall, those reductions related to decreased parasympathetic and increased sympathetic outflows. Autonomic fluctuations seemed to represent more a consequence than a cause of reduced PWR.

Personalized physiologic flow waveforms improve wave reflection estimates compared to triangular flow waveforms in adults

2021 ◽  
Author(s):  
Ninette Shenouda ◽  
Joseph M. Stock ◽  
Jordan C. Patik ◽  
Julio A. Chirinos ◽  
David G Edwards
Keyword(s):  
Wave Reflection ◽  
Systolic Pressure ◽  
Aortic Pressure ◽  
Flow Waveform ◽  
Prognostic Information ◽  
Triangular Waveform ◽  
Wave Separation ◽  
Measured Flow ◽  
Flow Waveforms ◽  
Central Pulse Pressure

Central aortic pressure waveforms contain valuable prognostic information in addition to central systolic pressure. Using pressure-flow relations, wave separation analysis can be used to decompose aortic pressure waveforms into forward- (Pf) and backward-travelling (Pb) components. Reflection magnitude, the ratio of pressure amplitudes (RM=Pb/Pf), is a predictor of heart failure and all-cause mortality. Aortic flow can be measured via Doppler echocardiography or estimated using a triangular flow waveform; however, the latter may underestimate the flow waveform convexity and overestimate Pb and RM. We sought to determine the accuracy of a personalized synthetic physiologic flow waveform, compared to triangular and measured flow waveforms, for estimating wave reflection indices in 49 healthy young (27±6 yrs) and 29 older adults (66±6 yrs; 20 healthy, 9 CKD). Aortic pressure and measured flow waveforms were acquired via radial tonometry and echocardiography, respectively. Triangular and physiologic flow waveforms were constructed from aortic pressure waveforms. Compared to the measured flow waveform, the triangular waveform underestimated Pf in older, but not young, adults and overestimated Pb and RM in both groups. The physiologic waveform was equivalent to measured flow in deriving all wave reflection indices and yielded smaller mean absolute biases than the triangular waveform in all instances (p<0.05). Lastly, central pulse pressure was associated with triangular, but not physiologic, mean biases for Pb and RM independent of age or central arterial stiffness (p<0.05). These findings support the use of personalized physiologic flow waveforms as a more robust alternative to triangular flow waveforms when true flow cannot be measured.

Method for determining distribution of reflection sites in the arterial system

1996 ◽  
Vol 271 (5) ◽  
pp. H1807-H1813 ◽  
Author(s):  
F. Pythoud ◽  
N. Stergiopulos ◽  
N. Westerhof ◽  
J. J. Meister
Keyword(s):  
Aortic Pressure ◽  
Arterial System ◽  
Arterial Pulse ◽  
Main Reflection ◽  
Reflection Profile ◽  
Limited Power ◽  
Measurement Location ◽  
Different Levels ◽  
Amplitude Versus ◽  
Iliac Bifurcation

We developed a new method to determine the location and importance of reflection sites in the arterial system. The method is based on the decomposition of the aortic pressure wave into its forward and backward components, and it provides the reflection profile of the arterial system as a wave reflection site amplitude versus distance from the heart. The reflection profile can be seen as the response of the arterial system to a pressure delta pulse where reflections upstream from the measurement location have been eliminated. The method was successfully tested on a simple model loaded with a pure resistor, a two-element windkessel, and a bifurcating tube system. It was then applied to the aortic pressure and flow signals measured in six mongrel dogs whose aorta was occluded at different levels. The profiles obtained from measurements at control showed two main reflection regions, one located in the vicinity (0.1-0.2 m) of the heart and the other located in the region of the iliac bifurcation. All occlusions, even the most distant one at the iliac bifurcation, could be identified in both amplitude (amount of reflections) and distance from the heart. The spatial resolution of the profiles was approximately 0.1 m as a result of the limited power spectrum contained in the arterial pulse, and the identification of reflection sites decreased rapidly with the distance.

Propagation of pressure pulse in kangaroo arterial system

1985 ◽  
Vol 249 (3) ◽  
pp. R335-R340 ◽  
Author(s):  
A. P. Avolio ◽  
W. W. Nichols ◽  
M. F. O'Rourke
Keyword(s):  
Pressure Pulse ◽  
Wave Reflection ◽  
Pulse Contour ◽  
Ascending Aorta ◽  
Arterial System ◽  
Upper Body ◽  
Peripheral Arteries ◽  
Lower Body ◽  
Close Proximity ◽  
Uniform Tube

The pressure pulse contour in the ascending aorta of kangaroos is markedly different from that seen in other species, but the changes undergone by the pulse propagating along the aorta are quite similar. Alteration of wave contour and progressive amplification of the pulse in the distal aorta and peripheral arteries of other mammals have been attributed to elastic nonuniformity of the aorta and to peripheral wave reflection. In kangaroos the aorta approximates a uniform tube with essentially constant viscoelastic properties, whereas wave reflection from the lower body appears to be unusually intense and to emanate from a single functionally discrete reflecting site; this appears to be the result of arterial terminations in the muscular lower body. Intense wave reflection from the lower body is the dominant mechanism responsible for changes in the pressure pulse of kangaroos between the ascending aorta and peripheral arteries. Contour of the pulse in the ascending aorta is attributable to this and to close proximity of reflecting sites in the upper body.

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