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CS-100 (Cardio Scan– 100)
An ECG Acquisition and FCG (Frequency
CardioGram) Spectrum Analysis Systems
A Preliminary Screening Tool
To Detect Coronary Artery Diseases (CAD)
Early Ischemia to Myocardial Infarction
Theoretical Principle
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2. Schematic Flow Chart of CS-100
Electrodes
Time Domain Cardiac
Electrical Currents
ECG
Electrocardiogram
Complied and
Recorded
FFT (Fast Fourier
Transformation)
Into Frequency
Components
Digital Signal Analysis
(1) Energy Spectrum
(2) Phase Shift
Impulse Response
Cross-Correlation
Coherence
FCG
Frequency Cardiogram
and
Diagnostic Indexes
Index Value
- Data Base
(30,000 tests)
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HUMAN HEART
A dual functioning self-regulatory electrical engineering system
(1) A human heart is able to self generate the electrical currents in a regular
time Intervals which cause the heart muscle to contract and relax; and
(2) With the contraction and relaxation of the heart muscle, a heart becomes
a mechanical pump that pumps blood throughout the body.
(3) The mechanical movement and electrical activity of the heart system are
mutually coupled and mutually influenced.
(4) The frequency of heartbeat per minute coincides with the frequency of
Electrical charge and discharge cycle of the electrical system of the heart.
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Electrocardiograph (ECG)
ECG is a measurement of the cardio electrical signal, the physiologic events occurring within a human heart, in the time domain;
Any change in the physiology of a human heart will cause a unique corresponding change in the cardio electrical signal;
3. ECG waveform can display some, but not all the changes, specially the subtle or slight change;
4. From those changes in the ECG waveform to detect the presence of heart diseases with an average of 50% accuracy.
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Dynamics of the Human Heart
Blood is non-Newtonian fluid
Cardiac muscle is a viscous and elastic solid mass that exhibits a lagging effect
during its relaxation. It’s behavior is path-dependence, or has rate-independent
Memory , and mathematically forms a hysteresis loop.
As the heart beats with the increase of cycling, this lagging effect becomes
stable, and the area of the hysteresis loop diminishes and the curves that
form the loop become a straight line, thus can be looked upon as a system with
no hysteresis.
In a system with no hysteresis, it is possible to predict the system’s output
at an instant in time, given only it input at that instant in time. This kind of
predication is not possible for a system with hysteresis.
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FCG FIRST HYPOTHESIS
(1) Human Heart possesses a linear time-invariant (LTI) property in a
finite short segment of time of less than 2 minutes;
(2) ECG is a complex continuous periodic time dependent signal and
by ways of FFT (Fast Fourier Transformation) can be mathematically
decomposed, digitized, and transformed into a series of frequency
components. FFT does not physically create nor destroy any cardio
electrical signal.
(3) Apply the DIGITAL SIGNAL PROCESS (DSP), a difference approach, and
the use of a computer to probability assess the changes in the ECG.
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DIGITAL SIGNAL PROCESS (DSP)
LTI (Linear Time-Invariant) System:
(1) Linear System - a signal detected is the sum of the Individual outputs of
several individual inputs signal; and
(2) Time-Invariant System - wherever there is a time delay (or shift) in the
input sequence, it will have an equivalent time delay in the output
sequence.
DSP (Digital Signal Processing) Mathematic Equations -
(1) FFT (Fast Fourier Transformation)
(2) Evaluation – (1) Power Spectrum, (2) Phase Shift and (3) Impulse Response
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DIGITAL SIGNAL PROCESS (DSP) APPLICATION IN FCG
FFT (Fast Fourier Transformation)
To mathematically convert the time-domain ECG into its frequency components
by means of decomposition, digitization and transformation.
Evaluation Equations – Power Spectrum, Phase Shift and Impulse Response
- Use these equations to mathematically calculate all the frequency data of an
ECG detected from a patient; and
- from the result of each calculation, to probability assess how well the patient’s
heart is performing mechanically, and any presence of abnormality within the
cardiovascular system.
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Power Spectrum
An power spectrum is a plot of power uV verse frequency Hz. It is used to
describe how the energy of a time domain signal is distributed in frequency.
The tip Sx(f) is the energy reading at frequency point (f) in uV/Hz.
↑ ↑ uV
Hz →
Sx(f) is the amplitude of energy in uV for a frequency at (f) Hz point.
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Normal Power Spectrum - Six (6) Distinctive Characteristics
Same distance between two energy peaks with ascertain peak height ratio among the peaks;
First peak usually appears at 1.2 Hz, a number relates to heart beats per minute;
There are peaks within 0 – 25 Hz frequency range;
(4) Combined energy of the 1st to 5th peaks is 50% - 60% of the total energy;
The first peak (related to the T wave) takes up 1/3 of the total energy; and
(6) Peak height relationship among peaks having diagnostic value:
(a) 1st peak is higher then 2nd peak;
(b) 3rd peak is higher than 4th peak;
(c) 5th peak and peaks thereafter are all lower than the 1st peak
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Diagnostic Index Selection and Value
(1) Differential Diagnosis - It is a systematic method used to identify unknowns. It
essentially is a process of elimination used by physicians or other clinicians to
diagnose the specific disease in a patient.
(2) Probability Assessment – the probability of event is a number lying in the interval 0<p>1 with 0 corresponding to an event that never occurs, and 1 to an event that is certain to occur.
From (1) and (2), a number of indexes and their respective value were determined and selected.
239 persons with Coronary Heart Disease were tested, and 210 were correctly diagnosed which gives an accuracy rate of 88%.
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Power Spectrum - “+” index diagnostic Suggestion
H - 2nd / 1st > normal ratio
- Insufficient myocardial power due to insufficient blood supply
- Early warning of development of myocardial ischemia.
N - Low or no 1st peak and low or no 3rd or 4th peak
- myocardium injuries (recent or old).
B - 1st and/or 2nd peak is too high
- Cardiomyopathy (Ischemic) or Ventricular Hypertrophy
A - 5th / 1st > normal ratio
- Possible ischemia with compensation already set in, if H is “-“.
However, if H is “+”, then a more advanced ischemia
E - Any one or two peaks after 5th peak / 1st peak > normal ratio.
- myocardial compensation has already set in for one or more years.
- ischemic damages to myocardium.
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FCG 2nd Hypothesis
(Further Evaluation of left ventrical)
Following the first hypothesis;
Designate Lead V5 ECG current as the Input (exciting) current;
3. Designate Lead II ECG current as the Output Current.
Reasons for using these two currents are:
(a) These two ECG currents under a normal condition travel at the same
direction with a phase angle of 90 degree, and
(b) through the left ventricular area, this allows further evaluation of the left
ventrical of a human heart.
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DSP Application of Lead II and Lead V5
Applying the digital signal processing evaluation equations of
(1) transfer function in phase angle shift; and
(2) impulse response.
With differential diagnosis and probability assessment, FCG has identified
a total of five (5) indexes: one for the phase shift index (P) and a set of four
indexes for the impulse response (M, f, R, C) to have diagnostic
significance.
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Transfer Function in Phase Shift
Phase angle shifts spectrum – angle shift between +180 degree to -180 degree
Measured in every 2 Hz increment from 0Hz to 25Hz .
+ one unit zone - a rectangular zone starting from frequency 6Hz to 20Hz and
phase angle shift + 90 degree, the applicable measuring area.
A normal Phase Shift with the PS line traveling smoothly and close to the “0” line
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Phase Shift - Indexes P
(-) index - the phase shift line shall be relatively smooth traveling closely to the
middle zero degree line and within this + one unit zone – Normal condition.
Two types of (+) Index
(+) index - The Phase Shift line travels over and above the zero degree line (time
lead,) and/or below the zero degree line (time lag) – abnormal condition indicative
of early ischemia.
(+) index - When the phase shift line exhibits great deviation or oscillation, it is
indicative of conduction blockage and/or CAD.
See next page for (+) Phase Shift.
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Abnormal Phase Shift Response
A (+) P index - Phase shift line travels over and below the zero unit zone
A (+) P index – Phase Shift line exhibits great oscillation
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Phase Shift Mathematic Calculation
A phase shift between the input current and output current is called a “Transfer
Function in Phase Angle Shift” and can be measured by the following equation:
Өxy(f) = tan-1{Image Hxy(f) / Real Hxy(f)}
Whereas Өxy(f) is the phase shift of the electrical currant in degree. It can be positive
or negative within the range of +180 degree to -180 degree. Where as
Hxy(f) = Gxy(W)/Gxx(W). (Transfer Function in Amplitude ratio between the amplitude
of one lead x and that of the other lead y at (f) Hz frequency point.
Gxy(W) = Sx(f) x Sy(f). (Cross power of the amplitude of one lead x at (f) frequency
and that of the other lead y at the same frequency point.)
Gxx(W) = Sx(f) x Sx(f). (The power at (f) frequency point of lead x.)
Image Hxy(f) is a Hxy from an imaginary new heart
Real Hxy(f) is the measured value.
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FCG - Impulse Response
In the DSP, for a machine, when an electrical signal is excited at one point, its output
response for that point can be measured:
IHxy(f) = F -1[Hxy(f)], an inverse Fourier Transformation.
By measuring and observing the difference between the exciting current and its
output response, the engineer can evaluate the mechanical performance and in
turn locate the problem within the system.
FCG applies the same DSP principle to treats the electrical current from Lead-V5 as the
input (excited) current and that of Lead-II as the output current and measure the
Impulse Response of IHxy(f) and Hxy(f) at frequency point (f) from 0 Hz to 26 Hz.
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Impulse Response Diagnostic Indexes
FCG identified four (4) indexes for diagnostic purpose – M, f, R, C.
a normal Impulse Response
All four diagnostic indexes are (-).
A normal Impulse response spectrum displays a narrow sharp tall main peak
pointing up above the base line at the middle zero point with no sub-response
( a smooth line) on either side of the middle zero point.
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Positive (+) Impulse Response Diagnostic Index
f - A significant negative reflected (inverted) main peak.
- Suggests a decreased compliance or conduction block or disturbance of reaction
function of the heart, usually caused by CAD, MI, ischemia or conduction
blockage.
M - Double or multi inverted main peak.
- Suggest poor conduction, increased in compliance, left ventricular malfunction.
R - Regular Sub-Response (RSR) peaks with one peak on each side of the main peak.
- Suggest unstable cardio electricity prior to the formation of MI caused by the
narrow arteries or existence of plaques deposit in the arteries.
- When there is an increase in RSR peak height, the possibility of re-occurrence
MI increases.
- R provides preventive diagnostic value in early detection of MI.
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Positive (+) Impulse Response Diagnostic Index
C - Causal Sub-Response(CSR) peaks - one or more peaks on each side of the main
peak.
- Suggest unstable cardio electrical activities at the beginning of contraction,
possible existence of the latent arrhythmia.
Multiple peak (some inversed) at the center with RSR peaks on each side
Multiple peaks (some inversed) at the center with several CSR peaks on each side
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