Exaggerated wave reflection in the kangaroo simulates arterial counterpulsation

1984 ◽  
Vol 246 (2) ◽  
pp. R267-R270
Author(s):  
A. P. Avolio ◽  
W. W. Nichols ◽  
M. F. O'Rourke
Keyword(s):  
Pressure Wave ◽  
Wave Reflection ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Peripheral Circulation ◽  
Aortic Pressure ◽  
Pulse Contour ◽  
Aortic Impedance ◽  
Intra Aortic Balloon Counterpulsation ◽  
Balloon Counterpulsation

The ascending aortic pressure wave in kangaroos is quite different from that seen in other experimental animals and in humans, despite an ascending aortic flow wave that is virtually identical. The diastolic pressure surge in the ascending aortic pressure wave of kangaroos is very prominent--so much so that peak diastolic pressure is often greater than peak systolic pressure, with the pressure wave resembling that recorded in humans during intra-aortic balloon counterpulsation. Ascending aortic impedance patterns in kangaroos indicate the presence of a single functionally discrete reflecting site in the peripheral circulation, with high reflection coefficient. All findings--of pulse contour and impedance patterns--are explicable on the basis of arterial anatomy and body shape. Wave reflection from the distant, large, and vascular lower body appears to dominate the effects of wave reflection from the short, small, and less vascular head and forelimb 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.

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.

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.

Abstract 2097: Acute Ventricular Unloading in Dogs with Chronic Heart Failure: Comparison Between Intra-Aortic Balloon Counterpulsation and Continuous Aortic Flow Augmentation

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Mengjun Wang ◽  
Robert Brewer ◽  
Itamar Ilsar ◽  
Alice Jiang ◽  
Tony Viole ◽  
...  
Keyword(s):  
Heart Failure ◽  
Diastolic Pressure ◽  
Decompensated Heart Failure ◽  
Aortic Flow ◽  
Acute Therapy ◽  
Systolic Volume ◽  
End Diastolic Volume ◽  
End Systolic Volume ◽  
Intra Aortic Balloon Counterpulsation ◽  
Balloon Counterpulsation

Background: Continuous aortic flow augmentation (CAFA) therapy provided by the Cancion ® system (Orqis Medical, Inc.) for decompensated heart failure (HF)has been shown to effectively unload the left ventricle (LV) in dogs with chronic HF. In the present study, we compared the extent of acute LV unloading elicited by CAFA to that elicited by intra-aortic balloon counterpulsation (IABP) in normotensive dogs with HF produced by multiple sequential intracoronary microembolizations. Methods: Studies were performed in 6 dogs with HF. Each dog was studied with CAFA and with IABP. Studies were performed one week apart. For each study, therapy with CAFA or IABP was maintained for 4 hours. The Cancion system was positioned using a dual femoral approach configuration with constant pump flow of 250 ml/min thus superimposing an element of continuous flow on existing pulsatile aortic flow. In all dogs and with both devices, LV end-diastolic pressure (LVEDP), LV end-diastolic volume (EDV), LV end-systolic volume (ESV) and LV ejection fraction (EF) were measured at baseline prior to initiating therapy and were repeated at 2 hours and 4 hours after insituting CAFA or IABP. Results: Data (mean SEM) are shown in the table . Up to 4 hours of IABP had no significant effects on LVEDP, EDV, ESV or EF. In contrast, institution of CAFA for 4 hours significantly decreased LVEDP, EDV and ESV and significantly increased EF. Conclusions: In normotensive dogs with chronic HF and no epicardial coronary artery disease, acute therapy with IABP for up to 4 hours had no effect on LV unloading defined as a reduction in LV filling pressure and LV size. In the same cohort of dogs, CAFA therapy elicited marked LV unloading. These data indicate that CAFA is superior to IABP in achieving acute LV unloading in the setting of chronic HF not complicated by ongoing myocardial ischemia and/or cardiogenic shock.

Progressive Resistance Training Without Volume Increases Does Not Alter Arterial Stiffness and Aortic Wave Reflection

2007 ◽  
Vol 232 (9) ◽  
pp. 1228-1235 ◽  
Author(s):  
Darren P. Casey ◽  
Darren T. Beck ◽  
Randy W. Braith
Keyword(s):  
Resistance Training ◽  
Arterial Stiffness ◽  
Pressure Wave ◽  
Wave Reflection ◽  
Augmentation Index ◽  
Aortic Pressure ◽  
Control Group ◽  
Training Volume ◽  
Leg Extension ◽  
Peripheral Arterial

Endurance exercise is efficacious in reducing arterial stiffness. However, the effect of resistance training (RT) on arterial stiffening is controversial. High-intensity, high-volume RT has been shown to increase arterial stiffness in young adults. We tested the hypothesis that an RT protocol consisting of progressively higher intensity without concurrent increases in training volume would not elicit increases in either central or peripheral arterial stiffness or alter aortic pressure wave reflection in young men and women. The RT group ( n = 24; 21 ± 1 years) performed two sets of 8–12 repetitions to volitional fatigue on seven exercise machines on 3 days/week for 12 weeks, whereas the control group ( n = 18; 22 ± 1 years) did not perform RT. Central and peripheral arterial pulse wave velocity (PWV), aortic pressure wave reflection (augmentation index; AIx), brachial flow–mediated dilation (FMD), and plasma levels of nitrate/nitrite (NOx) and norepinephrine (NE) were measured before and after RT. RT increased the one-repetition maximum for the chest press and the leg extension ( P < 0.001). RT also increased lean body mass ( P < 0.01) and reduced body fat (%; P < 0.01). However, RT did not affect carotid-radial, carotid-femoral, and femoral-distal PWV (8.4 ± 0.2 vs. 8.0 ± 0.2 m/sec; 6.5 ± 0.1 vs. 6.3 ± 0.2 m/sec; 9.5 ± 0.3 vs. 9.5 ± 0.3 m/sec, respectively) or AIx (2.5% ± 2.3% vs. 4.8% ± 1.8 %, respectively). Additionally, no changes were observed in brachial FMD, NOx, NE, or blood pressures. These results suggest that an RT protocol consisting of progressively higher intensity without concurrent increases in training volume does not increase central or peripheral arterial stiffness or alter aortic pressure wave characteristics in young subjects.

Changes in finger-aorta pressure transfer function during and after exercise

2006 ◽  
Vol 101 (4) ◽  
pp. 1207-1214 ◽  
Author(s):  
Wim J. Stok ◽  
Berend E. Westerhof ◽  
John M. Karemaker
Keyword(s):  
Blood Pressure ◽  
Transfer Functions ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Aortic Pressure ◽  
Finger Blood Pressure ◽  
Mean Pressure ◽  
Catheter Tip ◽  
The Individual ◽  
Finger Pressure

Noninvasive finger blood pressure has become a surrogate for central blood pressure under widely varying circumstances. We tested the validity of finger-aorta transfer functions (TF) to reconstruct aortic pressure in seven cardiac patients before, during, and after incremental bicycle exercise. The autoregressive exogenous model method was used for calculating finger-aorta TFs. Finger pressure was measured noninvasively using Finapres and aortic pressure using a catheter-tip manometer. When applying the individual TFs found during rest for reconstruction of aortic pressure during all workloads, systolic pressure was increasingly underestimated, with large variation between subjects: +4.0 to −18.1 mmHg. In most subjects, diastolic pressure was overestimated: −3.9 to +5.5 mmHg. Pulse pressure estimation varied between +4.5 and −21.9 mmHg. In all cases, wave distortion was present. Postexercise, error in reconstructed aortic systolic pressure slowly declined, and diastolic pressure was overestimated. During rest, the TF gain had a minimum between 3.65 and 4.85 Hz (Fmin). During exercise, Fmin shifted to frequencies between 4.95 and 7.15 Hz at the maximum workload, with no change in gain. Postexercise, gain in most subjects shifted to values closer to unity, whereas Fmin did not return to resting values. Within each subject, aorta-Finapres travel time was linearly related to mean pressure. During exercise, Fmin was linearly related to both delay and heart rate. We conclude that, during increasing exercise, rest TFs give an increasingly unreliable reconstruction of aortic pressure, especially at higher heart rates.

scholarly journals The Age-Dependent Contribution of Aortic Incident and Reflected Pressure Waves to Central Blood Pressure in African-Americans

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Haroon Kamran ◽  
Jason M. Lazar ◽  
Rinkesh Patel ◽  
IIir Maraj ◽  
Heather Berman ◽  
...  
Keyword(s):  
Blood Pressure ◽  
African Americans ◽  
Wave Reflection ◽  
Age Groups ◽  
Systolic Pressure ◽  
Applanation Tonometry ◽  
Blood Pressure Elevation ◽  
Primary Determinant ◽  
Aortic Impedance ◽  
Older Subjects

Aging is associated with increased central aortic systolic pressure (CSP) and pulse pressure which are predictive of cardiovascular events. Mechanisms implicated for higher central pressures include a higher forward incident pressure wave (P1), higher augmented pressure (AP), and shorter reflected wave round trip travel time (Tr). African-Americans (AA) have more frequent and deleterious blood pressure elevation. Using applanation tonometry, we studied the association of age and CSP with P1 and AP in 900 AA subjects. Data showed that in subjects ≤50 years old, CSP was mediated by AP but not P1 or Tr, whereas in those >50, CSP was mediated by both AP and P1 and to a lesser extent by Tr. Predictive models were significant () for both age groups. In conclusion, wave reflection is the primary determinant of CSP in younger AA, while in older subjects, CSP is mediated by both the magnitude and timing of wave reflection as well as aortic impedance.

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