The electrocardiograph (ECG) is an instrument which records the electrical activity of the heart. ... ECG provides valuable information about a wide range of cardiac disorders such as the presence of an inactive part (infarction) or an enlargement (cardiac hypertrophy) of the heart muscle.

1. BIOMEDICAL RECORDERS
R.GOWRI
ASSISTANT PROFESSOR/ECE
KIT-KALAIGNAR KARUNANIDHI INSTITUTE OF TECHNOLOGY
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2. What are biopotentials
Biopotential:
 An electric potential that is measured between points in living cells, tissues, and
organisms, and which accompanies all biochemical processes.
 Also describes the transfer of information between and within cells
 This book focuses strictly on the measurement of potentials
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4. Electrocardiography (ECG)
 Measures galvanically the electric activity of the heart
 Well known and traditional, first measurements by
Augustus Waller using capillary electrometer (year 1887)
 Very widely used method in clinical environment
 Very high diagnostic value
1. Atrial
depolarization
2. Ventricular
depolarization
3. Ventricular repolarization
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5. ECG basics
 Amplitude: 1-5 mV
 Bandwidth: 0.05-100 Hz
 Largest measurement error sources:
 Motion artifacts
 50/60 Hz powerline interference
 Typical applications:
 Diagnosis of ischemia
 Arrhythmia
 Conduction defects
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6. ECG
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 Electrical activity of heart.
 Used in catheterization laboratories, coronary care
units and routine diagnostic applications in
cardiology.
 LEAD – Two electrodes are placed over different
areas of the heart, the resulting tracing of voltage
difference at any sites due to electrical activity of
heart.

7. EFFECTS OF ARTIFACTS
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 Interference from the power line
 Shifting of the baseline
 Muscle tremor

8. Vectorcardiogram (VCG or EVCG)
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 Instead of displaying the scalar amplitude (ECG
curve) the electric activation front is measured and
displayed as a vector
 It has amplitude and direction
 Diagnosis is based on the curve that the point of this
vector draws in 2 or 3 dimensions
 The information content of the VCG signal is roughly
the same as 12-lead ECG system. The advantage
comes from the way how this information is
displayed
 Increase in sensitivity
 A normal, scalar ECG curve can be formed from this
vector representation, although (for practical
reasons) transformation can be quite complicated

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 Display in 2 perpendicular axis
 Loop type pattern
 Provides direction of depolarization and
repolarization of atria and ventricle
 3 loops – P wave,QRS axis(high amp – predominate
and T wave.
 3 images – frontal,sagittal and transverse planes.
 Recognition of undetected atrial and ventricular
hypertrophy, myocardial infraction.
CONT…

10. 12-Lead ECG measurement
 Most widely used ECG measurement setup in clinical environment
 Signal is measured non-invasively with 9 electrodes
 Lots of measurement data and international reference databases
 Well-known measurement and diagnosis practices
 This particular method was adopted due to historical reasons, now it is already
rather obsoleteEinthoven leads: I, II & III Goldberger augmented leads: VR, VL & VF Precordial leads: V1-V6

11. CONT..
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12. PCG
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 Graphic record heart sound - Phonogram.
 Recording the sounds connected with the pumping
action of heart.
 Sound from heart – phonocardiogram
 Instrument to measure this – phonocardiograph
 Basic function – to pick up the different heart
sound,filter the required and display.
 Two categories –
 heart sound – transient characteristics with short
duration.(closing and opening of valves)
 murmurs – noisy characteristics with long
duration.(turbulent blood flow in heart)

13. Origin of sound
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 Valve closure
 Movement of heart wall
 Valve opening
 Extra cardiac sounds
1. Frequency – 10 to 1000 Hz.
LOW RANGE – 10 – 60 Hz(3rd and 4th)
MEDIUM RANGE – 60 – 150 Hz(1st and 2nd)
HIGH RANGE – 150 – 1000 Hz
2.Amplitude
3.Quality

14. Origin of sound
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 1st sound:
Closure of mitral and tricuspid valves.
Freq – 30 to 100 Hz and duration 50 to 100 ms
 2nd sound:
Closure of aortic and pulmonary valves(slight back
flow of blood).
Freq – 30 to 100 Hz and duration 25 to 50 ms .
 3rd and 4th low intensity and inaudible.(heard among
children).

15. Origin of sound
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 3rd sound:
Blood rapid movement into relaxed ventricular
chambers
Freq – 10 to 100 Hz and duration 0.04 to 0.08 s.
 4th sound:
atrial contraction.
Freq – 10 to 50 Hz and duration 0.03 to 0.06 s.

16. CONT..
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 Microphones for PCG:
Crystal microphone – contains wafer of piezo-
electric material, which generates potentials when
subjected to mechanical stresses due to heart sound.
Smaller in size, high sensitivity.
Dynamic microphone – consists of a moving coil
having a fixed magnetic core inside it. The coil moves
with the heart sound and produce a voltage because
of interaction with the magnetic flux.
New acoustic sensors – polymer based adherent
differential-output sensors.

17. Writing methods
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 Light beam galvanometer – expensive and require
more power from amplifiers when used for high freq.
 Direct writing recorders – upper freq 150 Hz.(used
for only low freq).
 Technique – envelope detection.
Fans, Air conditioners and other noise producing
gadgets will result in artefacts on the recordings.

18. Heart Sounds
 S1 – onset of the ventricular contraction
 S2 – closure of the semilunar valves
 S3 – ventricular gallop
 S4 – atrial gallop
 Other – opening snap, ejection sound
 Murmurs
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19. RECORDING SET - UP
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CONDENSE
R
MICROPHO
NE
ECG AMP
ECG
ELECTRODE
FILTER
PHONO
AMPLIFIER
FM TAPE
RECORDER
MONITOR
SCOPE

20. MEDICAL APPLICATION
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 Rheumatic valvular lesions
Allergic disease in which the heart valves are likely to be damaged. This creates
abnormal heart sound.
 The murmurs of aortic steonosis
The blood is ejected from the left ventricles through a small opening of aortic
valve. High pressure 350 mm of Hg and causes turbulent flow of blood.
 The murmurs of aortic regurgitation
During diastole, blood flow backward from aorta to left ventricles,causing a
blowing murmur.
 The murmurs of mitral regurgitation
During systole, blood flow backward through mitral valve.
 The murmurs of mitral steonosis
It produce murmurs when,Blood passes with difficulty from LA into the LV
due to pressure difference.

21. SPECIAL APPLICATION OF PCG
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 Fetal PCG
 Esophageal PCG
 Tracheal PCG - Cannula

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