scholarly journals Determination of Aortic Characteristic Impedance and Total Arterial Compliance From Regional Pulse Wave Velocities Using Machine Learning: An in-silico Study

2021 ◽  
Vol 9 ◽  
Author(s):  
Vasiliki Bikia ◽  
Georgios Rovas ◽  
Stamatia Pagoulatou ◽  
Nikolaos Stergiopulos
Keyword(s):  
In Silico ◽  
Pulse Wave ◽  
Cuff Pressure ◽  
Arterial Compliance ◽  
Characteristic Impedance ◽  
Cross Sectional ◽  
Non Invasive ◽  
Total Arterial Compliance ◽  
Aortic Characteristic Impedance

In-vivo assessment of aortic characteristic impedance (Zao) and total arterial compliance (CT) has been hampered by the need for either invasive or inconvenient and expensive methods to access simultaneous recordings of aortic pressure and flow, wall thickness, and cross-sectional area. In contrast, regional pulse wave velocity (PWV) measurements are non-invasive and clinically available. In this study, we present a non-invasive method for estimating Zao and CT using cuff pressure, carotid-femoral PWV (cfPWV), and carotid-radial PWV (crPWV). Regression analysis is employed for both Zao and CT. The regressors are trained and tested using a pool of virtual subjects (n = 3,818) generated from a previously validated in-silico model. Predictions achieved an accuracy of 7.40%, r = 0.90, and 6.26%, r = 0.95, for Zao, and CT, respectively. The proposed approach constitutes a step forward to non-invasive screening of elastic vascular properties in humans by exploiting easily obtained measurements. This study could introduce a valuable tool for assessing arterial stiffness reducing the cost and the complexity of the required measuring techniques. Further clinical studies are required to validate the method in-vivo.

Echocardiographic assessment of aortic elastic properties with automated border detection in an ICU: in vivo application of the arctangent Langewouters model

2005 ◽  
Vol 288 (5) ◽  
pp. H2504-H2511 ◽  
Author(s):  
Jan R. Heerman ◽  
Patrick Segers ◽  
Carl D. Roosens ◽  
Frank Gasthuys ◽  
Pascal R. Verdonck ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Arterial Compliance ◽  
Ascending Aorta ◽  
Border Detection ◽  
Cross Sectional ◽  
Ultrasound Monitoring ◽  
Total Arterial Compliance ◽  
Pressure Area ◽  
Echocardiographic Assessment

We studied whether combined pressure and transesophageal ultrasound monitoring is feasible in the intensive care unit (ICU) setting for global cardiovascular hemodynamic monitoring [systemic vascular resistance (SVR) and total arterial compliance (CPPM)] and direct estimation of local ascending and descending aortic mechanical properties, i.e., distensibility and compliance coefficients (DC and CC). Pressure-area data were fitted to the arctangent Langewouters model, with aortic cross-sectional area obtained via automated border detection. Data were measured in 19 subjects at baseline, during infusion of sodium nitroprusside (SNP), and after washout. SNP infusion lowered SVR from 1.15 ± 0.40 to 0.80 ± 0.32 mmHg·ml−1·s ( P < 0.05), whereas CPPM increased from 0.87 ± 0.46 to 1.02 ± 0.42 ml/mmHg ( P < 0.05). DC and CC increased from 0.0018 ± 0.0007 to 0.0025 ± 0.0009 l/mmHg ( P < 0.05) and from 0.0066 ± 0.0028 to 0.0083 ± 0.0026 cm2/mmHg ( P < 0.05), respectively, at the descending, but not ascending, aorta. The Langewouters model fitted the descending aorta data reasonably well. Assessment of local mechanical properties of the human ascending aorta in a clinical setting by automated border detection remains technically challenging.

Use of pulse pressure method for estimating total arterial compliance in vivo

1999 ◽  
Vol 276 (2) ◽  
pp. H424-H428 ◽  
Author(s):  
N. Stergiopulos ◽  
P. Segers ◽  
N. Westerhof
Keyword(s):  
Pulse Pressure ◽  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Aortic Pressure ◽  
Lower Limbs ◽  
Pressure Method ◽  
Total Arterial Compliance ◽  
The Difference ◽  
Pulse Pressure Method

We determined total arterial compliance from pressure and flow in the ascending aorta of seven anesthetized dogs using the pulse pressure method (PPM) and the decay time method (DTM). Compliance was determined under control and during occlusion of the aorta at four different locations (iliac, renal, diaphragm, and proximal descending thoracic aorta). Compliance of PPM gave consistently lower values (0.893 ± 0.015) compared with the compliance of DTM (means ± SE; r = 0.989). The lower compliance estimates by the PPM can be attributed to the difference in mean pressures at which compliance is determined (mean pressure, 81.0 ± 3.6 mmHg; mean diastolic pressure, over which the DTM applies, 67.0 ± 3.6 mmHg). Total arterial compliance under control conditions was 0.169 ± 0.007 ml/mmHg. Compliance of the proximal aorta, obtained during occlusion of the proximal descending aorta, was 0.100 ± 0.007 ml/mmHg. Mean aortic pressure was 80.4 ± 3.6 mmHg during control and 102 ± 7.7 mmHg during proximal descending aortic occlusion. From these results and assuming that upper limbs and the head contribute as little as the lower limbs, we conclude that 60% of total arterial compliance resides in the proximal aorta. When we take into account the inverse relationship between pressure and compliance, the contribution of the proximal aorta to the total arterial compliance is even more significant.

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.

Estimation of total arterial compliance: an improved method and evaluation of current methods

1986 ◽  
Vol 251 (3) ◽  
pp. H588-H600 ◽  
Author(s):  
Z. Liu ◽  
K. P. Brin ◽  
F. C. Yin
Keyword(s):  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Aortic Pressure ◽  
Arterial System ◽  
Windkessel Model ◽  
Total Arterial Compliance ◽  
Improved Methods ◽  
Mean Aortic Pressure

Determination of arterial compliance in vivo has long interested physiologists. Most current methods for estimating this parameter assume that compliance is constant, i.e., that arterial pressure-volume (P-V) relations are linear, and they also assume that diastolic aortic pressure decay is an exponential function of time. Both of these assumptions, however, are questionable. This study proposes improved methods of estimating compliance based on a Windkessel model of the arterial system but which utilize the area under the pressure tracing rather than the waveform itself. Formulations accounting for both linear and three hypothetical nonlinear arterial P-V relations (exponential, logarithmic, and parabolic) are presented. Data from patients with congestive heart failure and hypertension are used for illustration. Compliances assuming linear P-V relations are reasonably close to those assuming nonlinear P-V relations only at mean aortic pressure. At end-diastolic pressure the linear assumption underestimates and at peak systolic it overestimates the compliances obtained assuming nonlinear P-V relations. The simpler linear assumption still allows a first approximation to compliance, but we show that existing methods for obtaining compliance under this assumption have severe theoretical as well as practical shortcomings. Our proposed method avoids these shortcomings primarily because deviations from an exact exponential form of the pressure wave have less influence on these compliance estimates than currently used methods.

Apparent arterial compliance

1998 ◽  
Vol 274 (4) ◽  
pp. H1393-H1403 ◽  
Author(s):  
Christopher M. Quick ◽  
David S. Berger ◽  
Abraham Noordergraaf
Keyword(s):  
Pulse Wave Velocity ◽  
Wave Velocity ◽  
Pulse Wave ◽  
Arterial Compliance ◽  
Complex Function ◽  
Peripheral Resistance ◽  
Aortic Pressure ◽  
Arterial System ◽  
Lumped Model ◽  
Total Arterial Compliance

Recently, there has been renewed interest in estimating total arterial compliance. Because it cannot be measured directly, a lumped model is usually applied to derive compliance from aortic pressure and flow. The archetypical model, the classical two-element windkessel, assumes 1) system linearity and 2) infinite pulse wave velocity. To generalize this model, investigators have added more elements and have incorporated nonlinearities. A different approach is taken here. It is assumed that the arterial system 1) is linear and 2) has finite pulse wave velocity. In doing so, the windkessel is generalized by describing compliance as a complex function of frequency that relates input pressure to volume stored. By applying transmission theory, this relationship is shown to be a function of heart rate, peripheral resistance, and pulse wave reflection. Because this pressure-volume relationship is generally not equal to total arterial compliance, it is termed “apparent compliance.” This new concept forms the natural counterpart to the established concept of apparent pulse wave velocity.

Development of systemic arterial mechanical properties from infancy to adulthood interpreted by four-element windkessel models

2007 ◽  
Vol 103 (1) ◽  
pp. 66-79 ◽  
Author(s):  
Roberto Burattini ◽  
Paola Oriana Di Salvia
Keyword(s):  
Arterial Compliance ◽  
Peripheral Resistance ◽  
New Paradigm ◽  
Rapid Reduction ◽  
Cross Sectional ◽  
Total Arterial Compliance ◽  
In Series ◽  
Aortic Impedance ◽  
Age Range ◽  
Bell Shaped Curve

Aortic impedance data of infants, children and adults (age range 0.8–54 yr), previously reported by others, were interpreted by means of three alternative four-element windkessel models: W4P, W4S, and IVW. The W4P and W4S are derived from the three-element windkessel (W3) by connecting an inertance ( L) in parallel or in series, respectively, with the aortic characteristic resistance ( Rc). In the IVW, L is connected in series with a viscoelastic windkessel (VW). The W4S and IVW (same input impedance) fit the data best. The W4S, however, suffers from the assumption that Rc is part of total peripheral resistance ( Rp). The IVW model offers a new paradigm for interpretation of resistive properties in terms of viscous ( Rd) properties of vessel wall motion, distinguished from Rp. Results indicated that rapid reduction of Rd/ Rp during early development is functional to modulation of decay time constant (τd) of pressure in diastole, such that normalization over heart period (τd/T) is independent of body size. Estimates of total arterial compliance ( C) vs. age were fitted by a bell-shaped curve with a maximum at 33 yr. With body weight (BW) factored out by normalization, the C/BW data scattered about a bell-shaped curve centered at 66 mmHg. Inertance was significantly higher in pediatric patients than in adults, in accordance with a lower cross-sectional area of the vasculature, commensurate to a lower aortic flow. Changes of arterial properties appear functional to control the ratio of pulsatile power to active power and keep arterial efficiency as high as 97% in infants and children.

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.

scholarly journals Arterial Flow and Diameter-based Blood Pressure Models-an In-silico Comparison

2021 ◽  
Author(s):  
Ana Carolina Gonçalves Seabra ◽  
Alexandre Ferreira da Silva ◽  
Thomas Stieglitz ◽  
Ana Belen Amado Rey
Keyword(s):  
Blood Pressure ◽  
In Silico ◽  
Model Comparison ◽  
Pulse Wave ◽  
Ex Vivo ◽  
Mean Difference ◽  
Arterial Tree ◽  
Non Invasive ◽  
Luminal Area ◽  
Ultrasound Sensor

<div>This paper investigates the best method for obtaining highly accurate blood pressure values in non-invasive measurements when using an ultrasound sensor. Deviations of the model should be less than 5 mmHg from the actual values. Different blood pressure models were analyzed and qualitatively compared. Relevant arterial parameters such as luminal area, flow velocity and pulse wave velocity, of 729 subjects were extracted from a computer simulated database and served as input parameters. Due to pulse wave variations through the arterial tree, such as viscoelasticity and arterial stiffness, the applied algorithms need to be specifically adapted to each arterial site. In-silico model comparison at different arterial sites were used to identify the parameters for individual equations that deduce the blood pressure at different arteries (carotid, brachial and radial). A linear model calibrated luminal area pulse wave to blood pressure and revealed to be most accurate model. The model was validated with a commercial pressure sensor in an ex-vivo experimental setup. The results showed an in-silico pulse pressure correlation of 0:978 and mean difference of (-2.134 ±2.477) mmHg at the radial artery and ex-vivo pressure correlation of 0:994 and mean difference of (0.554 ±2.315) mmHg.</div>

scholarly journals A Combined In Vivo, In Vitro, In Silico Approach for Patient-Specific Haemodynamic Studies of Aortic Dissection

2020 ◽  
Vol 48 (12) ◽  
pp. 2950-2964
Author(s):  
Mirko Bonfanti ◽  
Gaia Franzetti ◽  
Shervanthi Homer-Vanniasinkam ◽  
Vanessa Díaz-Zuccarini ◽  
Stavroula Balabani
Keyword(s):  
Aortic Dissection ◽  
In Silico ◽  
Clinical Decision ◽  
Patient Specific ◽  
Type B ◽  
Non Invasive ◽  
Cfd Models ◽  
Numerical Predictions

AbstractThe optimal treatment of Type-B aortic dissection (AD) is still a subject of debate, with up to 50% of the cases developing late-term complications requiring invasive intervention. A better understanding of the patient-specific haemodynamic features of AD can provide useful insights on disease progression and support clinical management. In this work, a novel in vitro and in silico framework to perform personalised studies of AD, informed by non-invasive clinical data, is presented. A Type-B AD was investigated in silico using computational fluid dynamics (CFD) and in vitro by means of a state-of-the-art mock circulatory loop and particle image velocimetry (PIV). Both models not only reproduced the anatomical features of the patient, but also imposed physiologically-accurate and personalised boundary conditions. Experimental flow rate and pressure waveforms, as well as detailed velocity fields acquired via PIV, are extensively compared against numerical predictions at different locations in the aorta, showing excellent agreement. This work demonstrates how experimental and numerical tools can be developed in synergy to accurately reproduce patient-specific AD blood flow. The combined platform presented herein constitutes a powerful tool for advanced haemodynamic studies for a range of vascular conditions, allowing not only the validation of CFD models, but also clinical decision support, surgical planning as well as medical device innovation.

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