Thoracic aortic pressure-flow relationships and vascular impedance in fetal sheep

1992 ◽  
Vol 263 (3) ◽  
pp. H824-H832
Author(s):  
B. L. Langille ◽  
S. L. Adamson
Keyword(s):  
Phase Velocity ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Wave Reflections ◽  
Fetal Sheep ◽  
Vascular Impedance ◽  
Near Term ◽  
Aortic Characteristic Impedance

Upper descending thoracic aortic pressures recorded from near-term fetal sheep resembled those recorded in mature animals, but diastolic thoracic aortic flows were much greater than those reported for adults. Furthermore, the pressure wave was not amplified during transmission along the aorta, as it is in adults. Descending thoracic impedance fell with increasing frequency to approximately 25% of resistance to steady flow and then showed oscillations typical of systems in which pulse wave reflections are important. Angiotensin II and norepinephrine infusions enhanced impedance oscillations and caused changes in apparent phase velocity in the aorta that were consistent with increased wave reflections. Angiotensin also increased aortic characteristic impedance from 0.0152 +/- 0.0013 to 0.0230 +/- 0.0024 mmHg.min.ml-1. The effects of nitroprusside infusions indicated reduced wave reflection effects. Embolization of the placenta and hindlimbs with 50-microns microspheres was used to elevate vascular resistance in these beds. Embolization caused aortic flow to fall to zero by late diastole, and changes in impedance and apparent phase velocity suggested increased wave reflections from the periphery. Characteristic impedance was increased to 0.0209 +/- 0.0031 mmHg.min.ml-1.

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.

scholarly journals Effects of Arterial Stiffness, Pulse Wave Velocity, and Wave Reflections on the Central Aortic Pressure Waveform

2008 ◽  
Vol 10 (4) ◽  
pp. 295-303 ◽  
Author(s):  
Wilmer W. Nichols ◽  
Scott J. Denardo ◽  
Ian B. Wilkinson ◽  
Carmel M. McEniery ◽  
John Cockcroft ◽  
...  
Keyword(s):  
Arterial Stiffness ◽  
Pulse Wave Velocity ◽  
Wave Velocity ◽  
Pulse Wave ◽  
Aortic Pressure ◽  
Pressure Waveform ◽  
Wave Reflections ◽  
Central Aortic Pressure

scholarly journals Effects of pacing modality on noninvasive assessment of heart rate dependency of indices of large artery function

2016 ◽  
Vol 121 (3) ◽  
pp. 771-780 ◽  
Author(s):  
Isabella Tan ◽  
Hosen Kiat ◽  
Edward Barin ◽  
Mark Butlin ◽  
Alberto P. Avolio
Keyword(s):  
Heart Rate ◽  
Arterial Stiffness ◽  
Pulse Pressure ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Augmentation Index ◽  
Large Artery ◽  
Rate Dependency ◽  
Wave Reflections

Studies investigating the relationship between heart rate (HR) and arterial stiffness or wave reflections have commonly induced HR changes through in situ cardiac pacing. Although pacing produces consistent HR changes, hemodynamics can be different with different pacing modalities. Whether the differences affect the HR relationship with arterial stiffness or wave reflections is unknown. In the present study, 48 subjects [mean age, 78 ± 10 (SD), 9 women] with in situ cardiac pacemakers were paced at 60, 70, 80, 90, and 100 beats per min under atrial, atrioventricular, or ventricular pacing. At each paced HR, brachial cuff-based pulse wave analysis was used to determine central hemodynamic parameters, including ejection duration (ED) and augmentation index (AIx). Wave separation analysis was used to determine wave reflection magnitude (RM) and reflection index (RI). Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). Pacing modality was found to have significant effects on the HR relationship with ED ( P = 0.01), central aortic pulse pressure ( P = 0.01), augmentation pressure ( P < 0.0001), and magnitudes of both forward and reflected waves ( P = 0.05 and P = 0.003, respectively), but not cfPWV ( P = 0.57) or AIx ( P = 0.38). However, at a fixed HR, significant differences in pulse pressure amplification ( P < 0.001), AIx ( P < 0.0001), RM ( P = 0.03), and RI ( P = 0.03) were observed with different pacing modalities. These results demonstrate that although the HR relationships with arterial stiffness and systolic loading as measured by cfPWV and AIx were unaffected by pacing modality, it should still be taken into account for studies in which mixed pacing modalities are present, in particular, for wave reflection studies.

scholarly journals Changes in hemodynamics associated with metabolic syndrome are more pronounced in women than in men

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Pauliina Kangas ◽  
Antti Tikkakoski ◽  
Jarkko Kettunen ◽  
Arttu Eräranta ◽  
Heini Huhtala ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Cardiovascular Risk ◽  
Impedance Cardiography ◽  
Pulse Wave ◽  
Characteristic Impedance ◽  
Whole Body ◽  
Cardiac Work ◽  
Head Up Tilt ◽  
Body Impedance ◽  
Aortic Characteristic Impedance

AbstractThe increase in cardiovascular risk associated with metabolic syndrome (MS) seems higher in women than in men. We examined hemodynamics during head-up tilt in 252 men and 250 women without atherosclerosis, diabetes, or antihypertensive medication, mean age 48 years, using whole-body impedance cardiography and radial pulse wave analysis. MS was defined according to Alberti et al. 2009. Men and women with MS presented with corresponding elevations of systolic and diastolic blood pressure (10-14%, p ≤ 0.001) versus controls. Supine pulse wave velocity (16–17%, p < 0.001) and systemic vascular resistance (7–9%, p ≤ 0.026), and upright cardiac output (6–11%, p ≤ 0.008) were higher in both MS groups than controls. Elevation of supine aortic characteristic impedance was higher in women than in men with MS (16% vs. 8%, p = 0.026), and in contrast to men, no upright impedance reduction was observed in women. When upright, women but not men with MS showed faster return of reflected pressure wave (p = 0.036), and smaller decrease in left cardiac work (p = 0.035) versus controls. The faster upright return of reflected pressure, lower upright decrease in left cardiac work, and higher elevation of aortic characteristic impedance may contribute to the greater increase in MS-related cardiovascular risk in women than in men.

scholarly journals Longitudinal Changes of Input Impedance, Pulse Wave Velocity, and Wave Reflection in a Middle-Aged Population

Hypertension ◽  
2021 ◽  
Author(s):  
Daime Campos-Arias ◽  
Marc L. De Buyzere ◽  
Julio A. Chirinos ◽  
Ernst R. Rietzschel ◽  
Patrick Segers
Keyword(s):  
Pulse Wave Velocity ◽  
Wave Velocity ◽  
Input Impedance ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Characteristic Impedance ◽  
Arterial System ◽  
Middle Aged ◽  
Cross Sectional ◽  
Aged Population

The changes experienced by the arterial system due to the aging process have been extensively studied but are incompletely understood. Within-subject patterns of changes in regards to input impedance and wave reflection parameters have not been assessed. The Asklepios study is a longitudinal population study including healthy (at onset) middle-aged subjects, with 974 males and 1052 females undergoing 2 rounds of measurements of applanation tonometry and ultrasound, 10.15±1.40 years apart. Carotid-femoral pulse wave velocity, aortic input impedance, and wave reflection parameters were assessed, and linear mixed-effects models were used to evaluate their longitudinal trajectories and determinants. Overall, the effective 10-year increase in pulse wave velocity was less than expected from first round cross-sectional data, and pulse wave velocity was found to accelerate more in women than in men. Interestingly, the increase in pulse wave velocity was not paralleled by a decrease in arterial volume compliance, particularly in younger males. Aortic root characteristic impedance decreased with age in younger subjects while it increased for the older subjects in the study. These changes suggest that aortic dilation and elongation may play an important role determining the longitudinal age-related changes in impedance parameters in middle-age. Wave reflection decreased with aging, whereas resistance increased in women and decreased in men. We conclude that the effective impact of aging on arterial system properties, in a middle-aged population, is not well reflected by cross-sectional studies. Future studies should assess the interaction between geometric remodeling and wall stiffening as determinants of pulsatile hemodynamics.

Effects of pulmonary embolism on pulmonary vascular impedance in dogs and minipigs

1998 ◽  
Vol 84 (3) ◽  
pp. 815-821 ◽  
Author(s):  
Marco Maggiorini ◽  
Serge Brimioulle ◽  
Didier De Canniere ◽  
Marion Delcroix ◽  
Robert Naeije
Keyword(s):  
Pulmonary Hypertension ◽  
Vascular Reactivity ◽  
Wave Reflection ◽  
Blood Clot ◽  
Autologous Blood ◽  
Characteristic Impedance ◽  
Hydraulic Power ◽  
Mean Pulmonary Arterial Pressure ◽  
Vascular Impedance ◽  
Lower Ratio

Pigs have been reported to present with a stronger pulmonary vascular reactivity than many other species, including dogs. We investigated the pulmonary vascular impedance response to autologous blood clot embolic pulmonary hypertension in anesthetized and ventilated minipigs ( n = 6) and dogs ( n = 6). Before embolization, minipigs, compared with dogs, presented with higher mean pulmonary arterial pressure (Ppa; by an average of 9 mmHg), a steeper slope of Ppa-flow (Q˙) relationships, and higher 0-Hz impedance (Z0) and first-harmonic impedance (Z1), without significant differences in characteristic impedance (Zc), and a lower ratio of pulsatile hydraulic power to total hydraulic power. Embolic pulmonary hypertension (mean Ppa: 40–55 mmHg) was associated with increased Z0 and Z1 in both species, but the minipigs had a steeper slope of Ppa/Q˙ plots and an increased Zc. At identical Q˙ and Ppa, minipigs still presented with higher Z1 and Zc and a lower ratio of pulsatile hydraulic power to total hydraulic power. The energy transmission ratio, defined as the hydraulic power in the measured waves divided by the hydraulic power in the forward waves, was better preserved after embolism in minipigs. No differences in wave reflection indexes were found before and after embolism. We conclude that minipigs, compared with dogs, present with a higher pulmonary vascular resistance and reactivity and adapt to embolic pulmonary hypertension by an increased Zc without earlier wave reflection. These differences allow for a reduced pulsatile component of hydraulic power and, therefore, a better energy transfer from the right ventricle to the pulmonary circulation.

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.

Efficacy of Cushing response during development in sheep

1991 ◽  
Vol 261 (2) ◽  
pp. H575-H582
Author(s):  
J. E. Backofen ◽  
R. C. Koehler ◽  
A. P. Harris ◽  
M. C. Rogers ◽  
R. J. Traystman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Cerebral Blood Flow ◽  
Peripheral Resistance ◽  
Aortic Pressure ◽  
Metabolic Demand ◽  
O2 Uptake ◽  
Fetal Sheep ◽  
Cushing Response ◽  
Near Term

Mean aortic pressure (MAP) increases (Cushing response) when intracranial pressure (ICP) approaches MAP. We elevated ICP to levels equivalent to normal baseline MAP with infusion of mock cerebrospinal fluid (CSF) into the lateral cerebral ventricles and contrasted responses in near-term fetal sheep, 1-wk-old lambs, and adult sheep anesthetized with pentobarbital sodium. With CSF infusion 1-wk-old lambs and adults produced sustained increases in MAP of 16 +/- 1 and 22 +/- 2 mmHg, respectively, over a 40-min period. However, cerebral blood flow fell 66 and 57%, and cerebral O2 uptake fell 34 and 37%, respectively. In the near-term fetus, MAP increased by 11 +/- 1 mmHg and cerebral blood fell 49% at 3 min of elevated ICP. However, by 15 min MAP had increased further (+17 +/- 2 mmHg) and cerebral blood flow was nearly restored. In contrast to postnatal sheep, cerebral O2 uptake was maintained throughout in the fetus. The mechanism of increased MAP differed among groups. In adults total peripheral resistance fell significantly, whereas in the fetus and lamb it remained constant. Cardiac output increased in each group, but, because of the fall in peripheral resistance, increased cardiac output was relatively more important to the rise in MAP in adults. In addition, marked vasoconstriction occurred in intestines and skin in the fetus. The Cushing response is well-developed in near-term fetal sheep. After birth it may lose its effectiveness in providing for the basal metabolic demand of the brain.

Computation of Aortic Pulse Wave Velocity and Aortic Extensibility from Pressure Gradient Measurements

1975 ◽  
Vol 53 (5) ◽  
pp. 940-946 ◽  
Author(s):  
Alain C. Lapointe ◽  
Fernand A. Roberge ◽  
Réginald A. Nadeau ◽  
Pierre S. Thiry ◽  
Gérard M. Tremblay
Keyword(s):  
Pulse Wave Velocity ◽  
Phase Velocity ◽  
Pressure Gradient ◽  
Wave Velocity ◽  
Pulse Wave ◽  
Time Derivative ◽  
Aortic Pressure ◽  
Aortic Pulse Wave Velocity ◽  
Time Shift ◽  
Aortic Valves

This study is concerned with the computation of aortic pulse wave velocity based on simultaneous recordings of the aortic pressure gradient and first-time derivative of aortic pressure. These variables were recorded by means of a double-lumen catheter introduced in the aorta of four anesthetized closed chest dogs, and connected to critically damped manometer systems. Results of aortic pulse wave velocity were then compared: (i) to the true phase velocity obtained from spectra of apparent phase velocity, and (ii) to the pulse wave velocity computed from the time shift between maximum slopes of the pressure wave. From the aortic valves to 37 cm down the aortic trunk, pulse wave velocity increased from 410–460 cm/s to approximately 600–800 cm/s. Based on the wave propagation equation presented of Bramwell and Hill (Bramwell, J. C, and Hill, A. V. 1922. Proc. R. Soc. 93, 298–306), volumetric extensibility coefficients were computed from pulse wave velocity data. Results indicated that, from the aortic valves to 37 cm down the aorta, the mean volumetric extensibility decreased from 0.43–0.56% ΔV/cm H2O to 0.16–0.25% ΔV/cm H2O (1 cm H2O = 94.1 N/m2).

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.

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