Surgery – Truss – Pad
Patent
1996-01-30
1997-12-09
Getzow, Scott M.
Surgery
Truss
Pad
A61B 50452
Patent
active
056949421
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/GB94/01117, filed May 20, 1994.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the analysis of heart waveforms and, more particularly, to the heart waveform represented by the measurement known as the Ventricular Late Potential (VLP).
2. Description of the Related Art
It is known to apply temporal fractals to the study of cardiac rhythm (See, Goldberger et al., Experimental 1988; 44:983-987 and other citations in IEEE Engineering in Medicine and Biology, 1992, June p52). Goldberger suggests that disease states may lead to a loss of the physiological complexity of measurements and therefore to greater regularity, not a greater irregularity, in the measured phenomenon.
SUMMARY OF THE INVENTION
It is an object of the invention to provide, from an analysis of ventricular late potential measurements, an indication of a parameter significant for clinical evaluation.
The invention provides a method of analysing Ventricular Late Potential (VLP), including determining a parameter related to the complexity of the VLP as a parameter for clinical evaluation.
According to the invention, there is provided a method of analysing Ventricular Late Potential (VLP) including computing the fractal dimension of the attractor for the VLP as a parameter for clinical evaluation.
Preferably the VLP attractor is in three dimensional voltage space, the voltage being ECG measurements.
The geometrical realization of the attractor, which need not be carried out to perform the invention, may be considered as a path in phase space defined by ECG voltages in three orthogonal directions.
The method may include an approximation to the fractal dimension of the attractor as the quotient of log(L)/log(DD), where L is the total length of the attractor and DD is the spheric extent diameter of the attractor. The approximation may be produced by the application of an algorithm, conveniently in the form of a flow chart.
The method may include assessing the ECG signals to define VLP onset and offset points. The assessment of the ECG signals may include signal-averaging and high-pass filtering and the taking of the absolute value of the filtered output.
In one assessment, the onset is defined as the vector magnitude combination exceeding a chosen mean or peak voltage. This may be 40 micro volts mean or 48 microvolts peak (mean.+-.20%). In one assessment the offset is defined as the mean voltage exceeding the mean noise level plus three times the standard deviation of the noise sample.
A fractal dimension in excess of 1.30 may be selected as the value indicating a risk of sudden cardiac death positive (SCD+) condition. The fractal dimension may be provided as a display or other output.
To optimise ECG signal collection, a particular form of amplifier may be employed including three operational amplifiers with a high gain in an early front end stage to minimise noise over a controlled bandwidth, which may be 0.1 to 1200 Hz, and low crosstalk, which may be below -90dB.
Spectral analysis of VLP may be performed to produce an assessment based on a discrete Hartley transform (DHT) vector spectrum by summing amplitude components between -f.sub.1 to -f.sub.2 and +f.sub.2 to +f.sub.1 where f.sub.1 is a number larger than f.sub.2. A value in the upper part of the range of an individual assessment for a group including persons believed healthy and persons believed to be SCD+ indicates risk of SCD+ and provides a parameter for clinical evaluation.
The basic fractal techniques are now becoming known from the works of several authors including B. B. Mandelbrodt, J. Feder and D. Stauffer and H. E. Stanley to which reference is directed for these techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a diagram of electrode positions on the front, sides and back of a human torso,
FIG. 2 is a flow chart for an algorithm for computing the fractal dimension of
REFERENCES:
patent: 5341811 (1994-08-01), Cano
G. Breithardt et al, "Standards for analysis of ventricular late potentials using high resolution or signal-averaged electrocardiography", European Heart Journal (1991) 12, 473-480.
Proceedings of Computers in Cardiology, IEEE Press USA, 23 Sep. 1991, Venice Italy pp. 549-551, D. Eylon et al "A Ventricular Model with a 3-D Fractal Conduction Network".
S.H. Liu, "Formation and Anomalous Properties of Fractals", IEEE Engineering in Med, and Biology Magazine, Jun. 1992, pp. 28-39.
W. Deering et al, "Fractal Physiology", IEEE Engineering in Med. and Biology Magazine, Jun. 1992, pp. 40-46.
Ary L. Goldberger, "Fractal Mechanisms in the Electrophysiology of the Heart", IEEE Engineer, in Med. and Biology Magazine, Jun. 1992, pp. 47-52.
L.S. Liebovitch et al, "Ion Channel Kinetics", IEEE Engineering in Med. and Biology Magazine, Jun. 1992, pp. 53-56.
H.E. Schepers et al, "Four Methods", IEEE Engineering in Med. and Biology Magazine, Jun. 1992, pp. 57-71.
C.Fortin et al, "Fractal Dimension", IEEE Engineering in Med. and Biology Magazine, Jun. 1992, pp. 65-71.
Proceedings of Computers in Cardiology, IEEE Press USA, 19 Sep. 989, Israel, pp. 137-140, O.Barenfeld et al "Simulation of Late Potentials Using a Computerized Three Dimensional Model of the Hearts Ventricles with Fractal Conduction System".
Annals of Biomedical Engineering, vol. 21, No.2,Mar. 1993,USA,pp. 125-134,O.Berenfeld et al "Modeling of the Hearts Venticular Conduction System Using Fractal Geometry: Spectral Analysis of the QRS Complex",See p. 130,left col.,line 9-p. 134,right col.,line 6.
Medical & Biological Engineering & Computing, vol. 30, No. 5, Sep. 1992, UK, pp. 495-502, H. Bakardjian "Ventricular Beat Classifier Using Fractal No. Clustering", See p. 497, left col., line 24-p. 501, left col., line 23.
Joint Congress of the 16th International Conference on Medical and Biological Engineering, UK, vol. 31, 7 Jul. 1991, Kyoto, JP, pp. S137-S146, Escalona,O.J. et al "Fast and Reliable QRS Alignment Technique for High Frequency Analysis of Signal Averaged ECG" See p. S138, left col., line 25-p. S139, right col., line 16.
Proceeding of the Annual International Conference of the IEEE Engineering in Medicine and Biology Sociaty, IEEE Press USA, vol.1, 4 Nov. 1988, New Orleans USA, pp. 7-8, G.Harris "A Novel Approach to Pattern Recognition in Real Time Arrhythmia Detection".
British Technology Group Limited
Getzow Scott M.
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