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.

Left ventricle-aortic coupling: prediction of contraction pattern

1984 ◽  
Vol 247 (4) ◽  
pp. H531-H540
Author(s):  
H. Piene ◽  
E. S. Myhre
Keyword(s):  
Time Course ◽  
Mechanical Performance ◽  
Computational Procedure ◽  
Aortic Pressure ◽  
Aortic Flow ◽  
Ventricular Pressure ◽  
Mean Values ◽  
Ventricular Afterload ◽  
Aortic Input Impedance ◽  
Aortic Impedance

In control heart beats of six open-chest dogs we established a relationship between ventricular diameter and change in volume during systolic ejection, described ventricular mechanical performance by a time-dependent pressure-diameter relationship, and represented ventricular afterload in subsequent variably loaded test beats by aortic input impedance calculated from aortic flow and pressure. Impedance was manipulated by means of an inflatable balloon in the aorta. A computational procedure was developed which combined the independent and general descriptions of ventricle (1 and 2 above) and load (3 above) to predict the time course and mean values of aortic pressure, flow, ventricular pressure, and diameter over a broad range of aortic impedance. Predicted data were compared with those directly observed at identical impedance. High degree of accordance between predicted and observed data of stroke volume, mean aortic and mean ventricular pressure was found, but diameter shortening was less accurately predicted. Previously assessed dependency of the ventricular pressure-volume-time relationship on aortic flow and "ejection history" was also incorporated in the calculations. This caused improved prediction of the flow pulse configuration, but the quality of predictions of mean values of pressures and flow was not enhanced.

Catecholamine Infusion versus Intraaortic Counterpulsation at the Initial Phase of Left Intraventricular Balloon Pumping in the Fibrillating Animal Heart

1993 ◽  
Vol 16 (2) ◽  
pp. 86-90 ◽  
Author(s):  
S. Stamatelopoulos ◽  
N. Zakopoulos ◽  
N. Saridakis ◽  
S. Stefanou ◽  
A. Adractas ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Experimental Study ◽  
Left Atrial ◽  
Initial Phase ◽  
Aortic Pressure ◽  
Aortic Flow ◽  
Aortic Blood ◽  
Aortic Blood Pressure ◽  
The Mean ◽  
The Difference

This experimental study compares the effect of catecholamine infusion to the effect of intraaortic counterpulsation (IABP) while initiating intraventricular balloon pumping (IVBP) in the fibrillating heart. In 12 dogs IVBP started immediately after the induction of ventricular fibrillation. Intravenous adrenaline or noradrenaline (at a progressively increasing infusion rate until the systolic aortic blood pressure was 120 mm Hg) was interchanged with IABP. The systolic aortic pressure, the aotic flow and the mean left atrial pressure were, respectively, 120.4 ± 0.5 mm Hg, 42 ± 4 mlkg-1min-1 and 18.7 ± 1.2 mm Hg (x ± SEM) ten min after initiating catecholamine infusion and 97 ± 5 mm Hg (with a 131 ± 4 mm Hg diastolic wave), 69.6 ± 4 mlkg-1min-1 and 16 ± 1.5 mm Hg ten min after initiating IABP. The difference in aortic flow was significant (p<0.001). The results indicate that a better aortic flow may be obtained by combining IVBP and IABP than IVBP and vasoconstrictive agents in the fibrillating heart. If IVBP, IABP and catecholamines are combined, both AF and AP may increase.

Comparative analysis of aortic impedance and wave reflection in ferrets and dogs

2002 ◽  
Vol 282 (1) ◽  
pp. H244-H255 ◽  
Author(s):  
R. Burattini ◽  
K. B. Campbell
Keyword(s):  
Animal Species ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Aortic Pressure ◽  
The Body ◽  
Frequency Range ◽  
Wave Travel ◽  
Arterial Model ◽  
Aortic Impedance ◽  
The Difference

Our modified version of the T-tube arterial model (consisting of two parallel, loss-free transmission paths terminating in lumped loads of complex and frequency-dependent nature) was applied to experimental measurements of ascending aortic pressure and of ascending and descending aortic flows taken from dogs and ferrets. Our aim was to provide quantitative evaluation of the aortic pressure and flow pulse wave components as they relate to the distribution of arterial properties and relate to wave travel and reflection in mammalians of consistently different size and shape. Estimated effective lengths (distances to effective reflection sites) of the head-end ( d h) and body-end ( d b) transmission paths were ∼12 and 30 cm, respectively, in the dog and 6.5 and 13 cm, respectively, in the ferret. These lengths and distributions of estimated arterial properties were consistent with the difference in the body size and with the more central location of the heart in the ferret's body than it is in the dog's body. In both animal species the ascending aortic pressure and flow waves could be interpreted in terms of forward and reflected components arising from the two distinct effective reflection sites, although the higher d h/ d b ratio in the ferret determined the presence of one broad, indistinct minimum in the modulus of ascending aortic impedance in the frequency range from 0 to 10 Hz, rather than two distinct minima as observed in the dog.

OS 13-06 GENERATION OF AORTIC FLOW VELOCITY FROM DERIVED AORTIC PRESSURE WAVEFORMS USING AGE-SPECIFIC AORTIC IMPEDANCE MODELLING

2016 ◽  
Vol 34 (Supplement 1) ◽  
pp. e209
Author(s):  
Audrey Adji ◽  
Thomas Weber ◽  
Caroline O’Brien ◽  
Michael O’Rourke ◽  
Alberto Avolio
Keyword(s):  
Flow Velocity ◽  
Aortic Pressure ◽  
Aortic Flow ◽  
Aortic Impedance

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.

scholarly journals Time-domain representation of ventricular-arterial coupling as a windkessel and wave system

2003 ◽  
Vol 284 (4) ◽  
pp. H1358-H1368 ◽  
Author(s):  
Jiun-Jr Wang ◽  
Aoife B. O'Brien ◽  
Nigel G. Shrive ◽  
Kim H. Parker ◽  
John V. Tyberg
Keyword(s):  
Time Domain ◽  
Aortic Pressure ◽  
Domain Model ◽  
Wave System ◽  
Reflected Waves ◽  
Arterial Hemodynamics ◽  
Arterial Model ◽  
Anesthetized Dogs ◽  
The Difference ◽  
Flow Waveforms

The differences in shape between central aortic pressure (PAo) and flow waveforms have never been explained satisfactorily in that the assumed explanation (substantial reflected waves during diastole) remains controversial. As an alternative to the widely accepted frequency-domain model of arterial hemodynamics, we propose a functional, time-domain, arterial model that combines a blood conducting system and a reservoir (i.e., Frank's hydraulic integrator, the windkessel). In 15 anesthetized dogs, we measured PAo, flows, and dimensions and calculated windkessel pressure (PWk) and volume (VWk). We found that PWk is proportional to thoracic aortic volume and that the volume of the thoracic aorta comprises 45.1 ± 2.0% (mean ± SE) of the total VWk. When we subtracted PWk from PAo, we found that the difference (excess pressure) was proportional to aortic flow, thus resolving the differences between PAo and flow waveforms and implying that reflected waves were minimal. We suggest that PAo is the instantaneous summation of a time-varying reservoir pressure (i.e., PWk) and the effects of (primarily) forward-traveling waves in this animal model.

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.

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.

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