scholarly journals -154-THE RELATIONSHIP BETWEEN AORTIC INPUT IMPEDANCE (CHARACTERISTIC IMPEDANCE) AND SYSTOLIC AORTIC PRESSURE

1986 ◽  
Vol 50 (6) ◽  
pp. 504
Author(s):  
Shigeki Morita ◽  
Izumi Kuboyama ◽  
Toshihide Asou ◽  
Jiro Tanaka ◽  
Kouichi Tokunaga ◽  
...  
Keyword(s):  
Input Impedance ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Impedance Characteristic ◽  
Aortic Input Impedance ◽  
The Relationship

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.

A novel servo-control system that imposes desired aortic input impedance on in situ rat heart

2000 ◽  
Vol 278 (3) ◽  
pp. H998-H1007 ◽  
Author(s):  
Hiroshi Miyashita ◽  
Masaru Sugimachi ◽  
Takayuki Sato ◽  
Toru Kawada ◽  
Toshiaki Shishido ◽  
...  
Keyword(s):  
Control System ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Side Branch ◽  
Aortic Flow ◽  
Aortic Input Impedance ◽  
Aortic Impedance ◽  
The Difference ◽  
Flow Waveforms

To clarify the pathophysiological role of dynamic arterial properties in cardiovascular diseases, we attempted to develop a new control system that imposes desired aortic impedance on in situ rat left ventricle. In 38 anesthetized open-chest rats, ascending aortic pressure and flow waveforms were continuously sampled (1,000 Hz). Desired flow waveforms were calculated from measured aortic pressure waveforms and target impedance. To minimize the difference between measured and desired aortic flow waveforms, the computer generated commands to the servo-pump, connected to a side branch of the aorta. By iterating the process, we could successfully control aortic impedance in such a way as to manipulate compliance and characteristic impedance between 60 and 160% of their respective native values. The error between desired and measured aortic flow waveforms was 70 ± 34 μl/s (root mean square; 4.4 ± 1.4% of peak flow), indicating reasonable accuracy in controlling aortic impedance. This system enables us to examine the importance of dynamic arterial properties independently of other hemodynamic and neurohumoral factors in physiological and clinical settings.

Assessment of Windkessel as a model of aortic input impedance

1988 ◽  
Vol 255 (4) ◽  
pp. H742-H753 ◽  
Author(s):  
D. Burkhoff ◽  
J. Alexander ◽  
J. Schipke
Keyword(s):  
Input Impedance ◽  
Impedance Spectrum ◽  
Aortic Pressure ◽  
Stroke Work ◽  
Windkessel Model ◽  
The Real ◽  
Wide Range ◽  
Aortic Input Impedance ◽  
Coupling Variables ◽  
Best Fit

To facilitate the analysis of aortic-ventricular coupling, simplified models of aortic input properties have been developed, such as the three-element Windkessel. Even though the impedance spectrum of the Windkessel reproduces the gross features of the real aortic input impedance, it fails to reproduce many of its details. In the present study we assessed the physiological significance of the differences between real and Windkessel impedance. We measured aortic input impedance spectra from five anesthetized open-chest dogs under a wide range of conditions. For each experimentally determined spectrum we estimated the corresponding values of the best-fit Windkessel parameters. By computer simulation we imposed both the real and best-fit Windkessel impedances on a model left ventricle and assessed the differences in seven different coupling variables. The analysis indicated that the Windkessel model provides a reasonable representation of afterload for purposes of predicting stroke volume, stroke work, oxygen consumption, and systolic and diastolic aortic pressures. However, the Windkessel model significantly underestimates peak aortic flow, slightly underestimates mean arterial pressure, and, of course, does not provide realistic aortic pressure and flow waveforms.

Aortic input impedance in normal man and arterial hypertension: its modification during changes in aortic pressure

1982 ◽  
Vol 16 (11) ◽  
pp. 646-656 ◽  
Author(s):  
JEAN P MERILLON ◽  
GUY J FONTENIER ◽  
JEAN F LERALLUT ◽  
MICHEL Y JAFFRIN ◽  
GILBERT A MOTTE ◽  
...  
Keyword(s):  
Arterial Hypertension ◽  
Input Impedance ◽  
Aortic Pressure ◽  
Aortic Input Impedance ◽  
Normal Man

Fumonisin-induced blockade of ceramide synthase in sphingolipid biosynthetic pathway alters aortic input impedance spectrum of pigs

2003 ◽  
Vol 284 (6) ◽  
pp. H2034-H2044 ◽  
Author(s):  
Peter D. Constable ◽  
Geoffrey W. Smith ◽  
George E. Rottinghaus ◽  
Mike E. Tumbleson ◽  
Wanda M. Haschek
Keyword(s):  
Signaling Pathway ◽  
Vascular Tone ◽  
Second Harmonic ◽  
Control Diet ◽  
Characteristic Impedance ◽  
Impedance Spectrum ◽  
Aortic Pressure ◽  
Systemic Resistance ◽  
Ceramide Synthase ◽  
Aortic Input Impedance

The sphingolipid signaling pathway appears to play an important role in regulating vascular tone. We examined the effect of fumonisin B1, a fungal toxin in corn that blocks ceramide synthase in the sphingolipid signaling pathway, on the ascending aortic impedance spectrum of pigs. Sixteen pigs were fed culture material containing fumonisin B1 (20 mg/kg body wt) ( n = 7) or a control diet ( n = 9) daily for 3 days and then instrumented under α-chloralose anesthesia for measurement of ascending aortic pressure and flow. Fumonisin ingestion increased serum sphinganine and sphingosine concentrations. Fumonisin ingestion also decreased cardiac output and characteristic impedance and increased the frequency of the first minimum impedance modulus, systemic vascular resistance, and the terminal, first, and second harmonic reflection coefficients, without changing mean arterial pressure. Thus blockade of ceramide synthase is accompanied by decreased vascular tone in systemic conduit arteries and increased vascular tone in systemic resistance vessels. The results indicate that the sphingolipid signaling pathway influences vascular tone in α-chloralose-anesthetized pigs.

Autoregressive analysis of aortic input impedance: comparison with Fourier transform

1991 ◽  
Vol 260 (3) ◽  
pp. H998-H1002 ◽  
Author(s):  
T. Kubota ◽  
R. Itaya ◽  
J. Alexander ◽  
K. Todaka ◽  
M. Sugimachi ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Input Impedance ◽  
Impedance Spectrum ◽  
Aortic Pressure ◽  
Accurate Estimate ◽  
Ar Model ◽  
Aortic Input Impedance ◽  
The Fourier Transform ◽  
Data Length ◽  
Autoregressive Analysis

We evaluated the advantages of the autoregressive (AR) model over the conventional Fourier transform in estimating aortic input impedance. In 10 anesthetized open-chest dogs, we digitized aortic pressure and flow at 200 Hz for 51.20 s under random ventricular pacing and subdivided them into five segments. We obtained aortic input impedance over the frequency range of 0.1-20 Hz both by AR model and by Fourier transform for various lengths of data, i.e., from one to four consecutive segments. For any given data length, the impedance spectrum estimated by the AR model was smoother than that obtained by the Fourier transform. To evaluate the accuracy of the estimated impedance, we predicted instantaneous aortic pressure of the fifth segment by convolving corresponding aortic flow with the impulse response of aortic input impedance. The prediction error was less with the AR model than that resulting from Fourier transform as long as the number of the segments was less than four. We conclude that the AR model provides a more accurate estimate of aortic input impedance than does the Fourier transform when data length is limited.

Measurement of aortic input impedance in rats

1994 ◽  
Vol 267 (5) ◽  
pp. H1907-H1915 ◽  
Author(s):  
G. F. Mitchell ◽  
M. A. Pfeffer ◽  
N. Westerhof ◽  
J. M. Pfeffer
Keyword(s):  
Time Domain ◽  
Input Impedance ◽  
Characteristic Impedance ◽  
Small Animal ◽  
Spatial Separation ◽  
Analog Filters ◽  
Aortic Blood Flow ◽  
Impedance Spectra ◽  
Aortic Input Impedance ◽  
New Time

Measurement of aortic input impedance in the rat is complicated by a high basal heart rate but is possible if appropriate compensation is made for frequency-dependent errors in modulus and phase resulting from analog filters in the equipment and from nonalignment of pressure and flow sensors. Because input impedance is a complex quantity, accurate values for both phase and modulus are required before meaningful interpretation of the data can be made. We measured aortic pressure and electromagnetic ascending aortic blood flow in mature, ether-anesthetized, open-chest male Wistar rats. Pressure and flow waveforms were averaged in the time domain and converted to Fourier series. Flow moduli were corrected for the measured frequency response of the flowmeter. Phase spectra were corrected by the classic frequency-domain and two new time-domain methods. Compensation for instrumentation errors was assessed at two different flowmeter filter settings in five animals. Reproducibility, variability, and the effects of vasoconstriction were assessed in 43 animals. Three methods of estimating characteristic impedance from the impedance spectra were evaluated and found to produce comparable results at baseline and following pharmacological elevation of blood pressure with graded methoxamine infusion. Physiologically equivalent values for phase, as assessed by comparing oscillatory power calculated from the impedance spectra, were obtained with each of the phase-correction techniques. The new time-domain methods facilitate the assessment of aortic input impedance in this small animal model because they do not require measurement of the spatial separation between pressure and flow transducers and pulse wave velocity in the proximal aorta.

Nonhuman primate model for regional wave travel and reflections along aortas

1987 ◽  
Vol 253 (2) ◽  
pp. H299-H306 ◽  
Author(s):  
R. D. Latham ◽  
B. J. Rubal ◽  
N. Westerhof ◽  
P. Sipkema ◽  
R. A. Walsh
Keyword(s):  
Renal Artery ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Reflection Coefficients ◽  
Middle Aged ◽  
Papio Anubis ◽  
Primate Model ◽  
Wave Speeds ◽  
Pulse Transmission ◽  
Aortic Input Impedance

Arterial pulse transmission and wave reflections were studied in five mature anesthetized baboons (Papio anubis) using multisensor micromanometry. Simultaneous pressures were recorded from the left ventricle and every 10 cm along the aorta and its terminal branches, and flow velocity was measured in the aortic root. Aortic input impedance and regional foot-to-foot and apparent phase velocities were calculated. Aortography provided dimensional data for local reflection coefficients. Regional foot-to-foot wave speeds were somewhat lower than corresponding segments in humans. Proximal aortic pressure waveforms and characteristic impedance (110 +/- 29 dyn X s X cm-5) were not characteristic of middle-aged humans. Reflection coefficients at the terminal aortic bifurcation (0.06) at the level of the renal artery branches (0.09) were less than those found in humans. We conclude that the junction of the renal artery branches and the aorta in the baboon is closely matched and represents much less of a discrete reflection site than in humans. Although the baboon may be used to study pulse transmission characteristics in the baboon, this species is not a good model for the proximal systemic reflective characteristics of normal middle-aged humans.

Influence of Volatile Anesthetics on Left Ventricular Afterload In Vivo

1996 ◽  
Vol 85 (1) ◽  
pp. 112-120 ◽  
Author(s):  
Dermot Lowe ◽  
Douglas A. Hettrick ◽  
Paul S. Pagel ◽  
David C. Warltier
Keyword(s):  
Systemic Vascular Resistance ◽  
Input Impedance ◽  
Minimum Alveolar Concentration ◽  
Aortic Pressure ◽  
Left Ventricular ◽  
Windkessel Model ◽  
Left Ventricular Afterload ◽  
Ventricular Afterload ◽  
Aortic Input Impedance ◽  
Flow Waveforms

Background This investigation examined the effects of desflurane and sevoflurane on quantitative indices of left ventricular afterload derived from aortic input impedance (Zin) interpreted using a three-element Windkessel model. Methods After Animal Care Committee approval, dogs (n = 8) were chronically instrumented for measurement of systemic hemodynamics including aortic blood pressure and flow. On separate days, aortic pressure and flow waveforms were recorded under steady-state conditions in the conscious state and after equilibration for 30 min at 1.1, 1.3, 1.5, and 1.7 minimum alveolar concentration of desflurane or sevoflurane. Aortic input impedance spectra were obtained via power spectral analysis of aortic pressure and flow waveforms. Characteristic aortic impedance (Zc) and total arterial resistance were calculated as the mean of the magnitude of Zin between 2 and 15 Hz and the difference between Zin at zero frequency and Zc, respectively. Total arterial compliance (C) was calculated from aortic pressure and flow waveforms using the Windkessel model. Results Desflurane and sevoflurane increased heart rate and decreased systolic, diastolic, and mean arterial pressure, left ventricular systolic pressure, left ventricular peak positive rate of increase in left ventricular pressure, percent segment shortening, and stroke volume. Sevoflurane, but not desflurane, decreased cardiac output. Desflurane, but not sevoflurane, decreased systemic vascular resistance. Desflurane decreased R (3,170 +/- 188 during control to 2441 +/- 220 dynes.second.centimeter-5 at 1.7 minimum alveolar concentration) and did not alter C and Zc. In contrast, sevoflurane increased C (0.57 +/- 0.05 during control to 0.79 +/- 0.05 ml/ mmHg at 1.7 minimum alveolar concentration) and Zc (139 +/- 10 during control to 194 +/- 14 dynes.second.centimeter-5 at 1.7 minimum alveolar concentration) but did not change R. Conclusions The results indicate that desflurane and sevoflurane produce substantially different effects on left ventricular afterload in chronically instrumented dogs. Desflurane-induced decreases in systemic vascular resistance occur primarily because of effects on arteriolar resistance vessels. In contrast, sevoflurane increased C and Zc concomitant with pressure-dependent reductions in aortic diameter, suggesting that this anesthetic may alter left ventricular afterload by affecting the mechanical properties of the aorta.

scholarly journals Aortic input impedance in heart failure.

Circulation ◽  
1978 ◽  
Vol 58 (3) ◽  
pp. 460-465 ◽  
Author(s):  
C J Pepine ◽  
W W Nichols ◽  
C R Conti
Keyword(s):  
Heart Failure ◽  
Input Impedance ◽  
Aortic Input Impedance
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