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Journal ArticleDOI

Physical basis of ballistocardiography. III.

01 Feb 1956-American Heart Journal (Elsevier)-Vol. 51, Iss: 2, pp 179-185
TL;DR: Two methods for calculating the amplitude characteristic of the high-frequency BCG, the difference in movement of subject and BCG taken into account, are compared and discussed.
About: This article is published in American Heart Journal.The article was published on 1956-02-01 and is currently open access. It has received 40 citations till now. The article focuses on the topics: Ballistocardiography.

Summary (1 min read)

INTRODUCTION

  • From these curves something is to be detected about the occurrences within the body.
  • D~x, = Fint (1) x,, fs and R, are the respective displacement, velocity, and acceleration of the body with mass m, with respect to the fixed BCG.
  • The authors have chosen this number, which is much lower than the d&a used by Nickerson and Mathers, because the high-frequency BCG usually is, as far as they know, damped to this extent.
  • If the BCG carries a load that is not fixed to the BCG (e.g., a subject), then the damping of the BCG differs from the above-mentioned case.

THE CURVES CONCERNING THE MIDDLE-FREQUENCY BALLISTOCARDIOGRAPH

  • Nickerson and Mathers also calculate the distortion appearing when a middle-frequency BCG is used (natural frequency about 1 to 2 c/s).
  • To calculate the amplitude distortion they use formula (lOa).
  • Apart from the influence of the relative movement, the middle-frequency BCG has only a suitable amplitude characteristic and phase characteristic if its amplitude is regarded as a measure of the velocity with which the center of gravity moves.
  • But then, the loaded BCG must be damped far more than critical.
  • Es comparate e discutite duo methodos de calcular le amplitude characteristic de1 ballistocardiographo a alte frequentia, con consideration de1 differentia de1 movimento de subject0 e ballistocardiographo.

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Citations
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Journal ArticleDOI
TL;DR: This study constitutes a first validation of the complete one-dimensional model using human pressure and flow data and supports the applicability of the 1-D model in the human circulation.
Abstract: 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.

575 citations

Journal ArticleDOI
TL;DR: A new mathematical model for the wall properties emerges, which accounts in quantitative terms for the frequency dependence of the Young modulus, stress-relaxation, creep, and hysteresis, and covers all the known aspects of the viscoelastic wall properties.

164 citations

Journal ArticleDOI
TL;DR: Derivation and description are presented of an electrical analog of the left ventricle and the systemic arterial tree that has fewer limitations than the mathematical model.

107 citations

Journal ArticleDOI
TL;DR: The study shows that assumptions made on the velocity profile while specifying inlet boundary conditions have little influence on the local haemodynamics in the aneurysm, provided that a sufficient extension of the afferent vasculature is considered and that geometry is the primary determinant of the flow field within theAneurismal sac.
Abstract: Haemodynamics is believed to play an important role in the initiation, growth and rupture of intracranial aneurysms. In this context, computational haemodynamics has been extensively used in an effort to establish correlations between flow variables and clinical outcome. It is common practice in the application of Dirichlet boundary conditions at domain inlets to specify transient velocities as either a flat (plug) profile or a spatially developed profile based on Womersley's analytical solution. This paper provides comparative haemodynamics measures for three typical cerebral aneurysms. Three dimentional rotational angiography images of aneurysms at three common locations, viz. basilar artery tip, internal carotid artery and middle cerebral artery were obtained. The computational tools being developed in the European project @neurIST were used to reconstruct the fluid domains and solve the unsteady Navier-Stokes equations, using in turn Womersley and plug-flow inlet velocity profiles. The effects of these assumptions were analysed and compared in terms of relevant haemodynamic variables within the aneurismal sac. For the aneurysm at the basilar tip geometries with different extensions of the afferent vasculature were considered to study the plausibility of a fully-developed axial flow at the inlet boundaries. The study shows that assumptions made on the velocity profile while specifying inlet boundary conditions have little influence on the local haemodynamics in the aneurysm, provided that a sufficient extension of the afferent vasculature is considered and that geometry is the primary determinant of the flow field within the aneurismal sac. For real geometries the Womersley profile is at best an unnecessary over-complication, and may even be worse than the plug profile in some anatomical locations (e.g. basilar confluence).

65 citations

Journal ArticleDOI
TL;DR: It is hopeful that the time has come when doctors will no longer be content to regard heart diseases from the purely anatomic viewpoint, and when a statement of the strength and coordination of the heart's contraction will be considered an essential part of the record of every cardiac case.
Abstract: From the foregoing account one can see that determined efforts have been made to identify sources of error in the force ballistocardiogram as a record of the resultant of the forces generated by the heart. In few other clinical methods has there been such an extensive hunt. Certainly nothing of much moment has turned up, although we found reason to believe that differences in vessel elasticity and in size of subject would have some effect on the relation between the record and the forces which originate it. An effect of the position of the heart and of arteriosclerosis would manifest itself only if the deviation from the normal was extreme. While various other uncertainties certainly exist, it seems unlikely that they are important. Clinicians are often forced to use methods which are not perfect and much trouble can be avoided by proper care in the preparation and use of normal standards. In the case of the ballistocardiogram the scatter of the normal population will be due not only to differences in the forcefulness of the hearts of healthy persons, but also to all the other factors which might have some effect on the proper recording of such forces, such as: differences in body size, body habitus, blood pressure, arteriosclerosis and the usual technical errors. But if we identify as abnormal only those outside the statistical limits of normality of such a healthy group, the odds are strongly in favor of a valid identification of abnormality of the cardiac forces. Using the data from the cadaver experiments as a test, one finds we can identify the magnitude of the acceleration of the blood with an accuracy about equal to that of the common clinical method of taking blood pressure. It is true that the Riva-Rocci method has greater errors inherent in it than most doctors realize; the point I wish to make is that despite such errors, much important clinical information has been secured by means of it, and its introduction into clinical medicine was responsible for a great advance. I am hopeful, therefore, that the time has come when doctors will no longer be content to regard heart diseases from the purely anatomic viewpoint, and when a statement of the strength and coordination of the heart's contraction will be considered an essential part of the record of every cardiac case. The ballistocardiogram provides a method of readily securing information on this point without causing the least discomfort to the patient.

43 citations

References
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Journal ArticleDOI
TL;DR: The motion of the body recorded by a sphygmograph applied to the head, by a photocell partly shaded by a ruler across the shins, or by a coil in a magnetic field provides a satisfactory ballistocardiogram.

90 citations

Frequently Asked Questions (1)
Q1. What are the contributions in this paper?

Ue-frequency BCG ( natural frequency about 1 to 2 c/s ) represents the velocity of the center of gravity, provided that the damping is much more than critical.