Influence of central and peripheral changes on the hydraulic input impedance of the systemic arterial tree

The early detection and intervention of artery stenosis is very important to reduce the mortality of cardiovascular disease. A novel method for predicting artery stenosis was proposed by using the input impedance of the systemic arterial tree and support vector machine (SVM). Based on the built transmission line model of a 55-segment systemic arterial tree, the input impedance of the arterial tree was calculated by using a recursive algorithm. A sample database of the input impedance was established by specifying the different positions and degrees of artery stenosis. A SVM prediction model was trained by using the sample database. 10-fold cross-validation was used to evaluate the performance of the SVM. The effects of stenosis position and degree on the accuracy of the prediction were discussed. The results showed that the mean specificity, sensitivity and overall accuracy of the SVM are 80.2%, 98.2% and 89.2%, respectively, for the 50% threshold of stenosis degree. Increasing the threshold of the stenosis degree from 10% to 90% increases the overall accuracy from 82.2% to 97.4%. Increasing the distance of the stenosis artery from the heart gradually decreases the overall accuracy from 97.1% to 58%. The deterioration of the stenosis degree to 90% increases the prediction accuracy of the SVM to more than 90% for the stenosis of peripheral artery. The simulation demonstrated theoretically the feasibility of the proposed method for predicting artery stenosis via the input impedance of the systemic arterial tree and SVM.

Download Full-text

Validation of a one-dimensional model of the systemic arterial tree

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00037.2009 ◽

2009 ◽

Vol 297 (1) ◽

pp. H208-H222 ◽

Cited By ~ 331

Author(s):

Philippe Reymond ◽

Fabrice Merenda ◽

Fabienne Perren ◽

Daniel Rüfenacht ◽

Nikos Stergiopulos

Keyword(s):

Constitutive Law ◽

Distributed Model ◽

Arterial Tree ◽

One Dimensional ◽

Continuity Equations ◽

Nonlinear Viscoelastic ◽

Model Predictions ◽

The One ◽

D Model ◽

Systemic Arterial Tree

A distributed model of the human arterial tree including all main systemic arteries coupled to a heart model is developed. The one-dimensional (1-D) form of the momentum and continuity equations is solved numerically to obtain pressures and flows throughout the systemic arterial tree. Intimal shear is modeled using the Witzig-Womersley theory. A nonlinear viscoelastic constitutive law for the arterial wall is considered. The left ventricle is modeled using the varying elastance model. Distal vessels are terminated with three-element windkessels. Coronaries are modeled assuming a systolic flow impediment proportional to ventricular varying elastance. Arterial dimensions were taken from previous 1-D models and were extended to include a detailed description of cerebral vasculature. Elastic properties were taken from the literature. To validate model predictions, noninvasive measurements of pressure and flow were performed in young volunteers. Flow in large arteries was measured with MRI, cerebral flow with ultrasound Doppler, and pressure with tonometry. The resulting 1-D model is the most complete, because it encompasses all major segments of the arterial tree, accounts for ventricular-vascular interaction, and includes an improved description of shear stress and wall viscoelasticity. Model predictions at different arterial locations compared well with measured flow and pressure waves at the same anatomical points, reflecting the agreement in the general characteristics of the “generic 1-D model” and the “average subject” of our volunteer population. The study constitutes a first validation of the complete 1-D model using human pressure and flow data and supports the applicability of the 1-D model in the human circulation.

Download Full-text

Pulse Propagation in the Systemic Arterial Tree

Vascular Dynamics ◽

10.1007/978-1-4684-7856-3_5 ◽

1989 ◽

pp. 49-67 ◽

Cited By ~ 6

Author(s):

Ricky D. Latham

Keyword(s):

Pulse Propagation ◽

Arterial Tree ◽

Systemic Arterial Tree

Download Full-text

Validation of 1D Model of the Systemic Arterial Tree Including the Cerebral Circulation

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-192529 ◽

2008 ◽

Author(s):

Philippe Reymond ◽

Fabrice Merenda ◽

Fabienne Perren ◽

Daniel Rüfenacht ◽

Nikos Stergiopulos

Keyword(s):

Cerebral Circulation ◽

Cerebral Arteries ◽

Distributed Model ◽

Heart Model ◽

Arterial Tree ◽

Distributed Models ◽

The Past ◽

1D Model ◽

Systemic Arterial Tree

The aim of this study is to develop a distributed model of the entire systemic arterial tree, coupled to a heart model and including a detailed description of the cerebral arteries. Distributed models of the arterial tree have been studied extensively in the past (Avolio [1], Stergiopulos et al [2], Westerhof et al [3]), however, no model has been developed so far that offers a physiologically relevant coupling to the heart and includes the entire cerebral arterial tree.

Download Full-text

A Hybrid Mock Circulatory System: Development and Testing of an Electro-hydraulic Impedance Simulator

The International Journal of Artificial Organs ◽

10.1177/039139880302600109 ◽

2003 ◽

Vol 26 (1) ◽

pp. 53-63 ◽

Cited By ~ 21

Author(s):

M. Kozarski ◽

G. Ferrari ◽

F. Clemente ◽

K. Górczyńska ◽

C. De Lazzari ◽

...

Keyword(s):

Input Impedance ◽

Numerical Models ◽

Peripheral Resistance ◽

Left Ventricular ◽

Physical Models ◽

Gear Pump ◽

Arterial Tree ◽

Windkessel Model ◽

Mock Circulatory System ◽

Hydraulic Impedance

Mock circulatory systems are used to test mechanical assist devices and for training and research purposes; when compared to numerical models, however, they are not flexible enough and rather expensive. The concept of merging numerical and physical models, resulting in a hybrid one, is applied here to represent the input impedance of the systemic arterial tree, by a conventional windkessel model built out of an electro-hydraulic (E-H) impedance simulator added to a hydraulic section. This model is inserted into an open loop circuit, completed by another hybrid model representing the ventricular function. The E-H impedance simulator is essentially an electrically controlled flow source (a gear pump). Referring to the windkessel model, it is used to simulate the peripheral resistance and the hydraulic compliance, creating the desired input impedance. The data reported describe the characterisation of the E-H impedance simulator and demonstrate its behaviour when it is connected to a hybrid ventricular model. Experiments were performed under different hemodynamic conditions, including the presence of a left ventricular assist device (LVAD).

Download Full-text

One Dimensional Model of the Systemic Arterial Tree Including Cerebral Circulation

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176452 ◽

2007 ◽

Cited By ~ 1

Author(s):

Philippe Reymond ◽

Fabrice Merenda ◽

Fabienne Perren ◽

Daniel Rüfenacht ◽

Nikos Stergiopulos

Keyword(s):

Cerebral Circulation ◽

Cerebral Arteries ◽

Distributed Model ◽

Dimensional Model ◽

Heart Model ◽

Arterial Tree ◽

One Dimensional ◽

Distributed Models ◽

The Past ◽

Systemic Arterial Tree

The aim of this study is to develop a distributed model of the entire systemic arterial tree, coupled to a heart model and including a detailed description of the cerebral arteries. Distributed models of the arterial tree have been studied extensively in the past (Avolio [1]; Cassot et al [2]; Meister [3]; Schaaf and Abbrecht [4]; Stergiopulos et al [5]; Westerhof et al [6]; Zagzoule and Marc-Vergnes [7]), however, no model has been developed so far that offers a physiologically relevant coupling to the heart and includes the entire cerebral artery network.

Download Full-text

Normalized input impedance and arterial decay time over heart period are independent of animal size

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.261.1.r126 ◽

1991 ◽

Vol 261 (1) ◽

pp. R126-R133 ◽

Cited By ~ 26

Author(s):

N. Westerhof ◽

G. Elzinga

Keyword(s):

Heart Rate ◽

Decay Time ◽

Input Impedance ◽

Diastolic Pressure ◽

Arterial Compliance ◽

Characteristic Impedance ◽

Peripheral Resistance ◽

Arterial System ◽

Heart Period ◽

Arterial Tree

The arterial system of mammals in the weight range from 0.6 to 70 kg is characterized by the three-element windkessel, a succinct representation of the arterial tree consisting of the parameters peripheral resistance (Rp), total arterial compliance (C), and aortic characteristic impedance (Zc). The values of these parameters in resting conditions are related to body mass (M). The time constant, or decay time (tau), of the arterial system (defining rate of decay of aortic pressure in diastole), the product of Rp and C, is also evaluated. The dependencies of the heart period (T, inverse of heart rate), and durations of ejection (Ts) and of diastole (Td) in resting conditions are also determined as a function of M. It is found that Rp = Rp0M-0.93; Zc = Zc0M-0.97; and C = C0M+1.23, where Rp0, Zc0, and C0 are proportionality constants. Zc is thus a constant fraction of Rp in all mammals. tau is related to M as tau = tau 0M+0.29; T and Td are related to M as T = T0M+0.27 and Td = Td0M+0.30, where tau 0, T0, and Td0 are proportionality constants. The duration of diastole is thus a constant fraction of T, and the ratios T/tau and Td/tau are independent of M. The findings indicate that arterial input impedance, normalized to aortic Zc and plotted as a function of frequency normalized to heart rate, is similar for all mammals. The finding that the ratio Td/tau is the same in mammals (and Ts/T and stroke volume/M are constant) explains the constancy of pulse pressure (systolic minus diastolic pressure).(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Scatter in input impedance spectrum may result from the elastic nonlinearity of the arterial wall

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1995.269.4.h1490 ◽

1995 ◽

Vol 269 (4) ◽

pp. H1490-H1495 ◽

Cited By ~ 3

Author(s):

N. Stergiopulos ◽

J. J. Meister ◽

N. Westerhof

Keyword(s):

Elastic Properties ◽

Input Impedance ◽

Arterial Wall ◽

Impedance Spectrum ◽

Arterial Tree ◽

Heart Rates ◽

Aortic Input Impedance ◽

Nonlinear Elastic ◽

Phase Angles ◽

Wave Shapes

We have examined the role of the nonlinear elastic properties of the arterial wall on the human aortic input impedance obtained at different heart rates and different pressure and flow wave shapes. Pressure and flow were taken from a computer model that provides realistic simulations of the nonlinear distributed systemic arterial tree. Different wave shapes of ascending aorta pressure and flow and different heart rates were used to derive input impedance moduli and phase angles via Fourier analysis. The results show that the nonlinear elastic properties of the arterial wall are responsible for significant variations in the input impedance spectrum when changes in heart rate and aortic flow wave shape take place. This finding may explain the scatter often observed in experimentally determined input impedance data using different heart rates obtained by pacing.

Download Full-text