Cardea Biomedical Labs New Delhi
Table Of Contents
1. Acknowledgements.
2. Certificate
3. Introduction to the project
4. Basics of ECG
5. Circuit diagram
6. Working of ECG
7. Matlab Basics
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
ACKNOWLEDGEMENT
It is with pleasure that we find ourselves penny down
these line to express our sincere thanks to various people to
help me along the way in completing this work.
I am helpful to Mr. B.S.Brar, Miss Gurwinder Kaur &
Mr. A.C. Mongra who gave me chance to go outside the
college for the training. Also thankful to Mr. Abinav, who
taught me during the 6 week training.
I also thankful to my parents & dearest who help me in
doing this report.
Sunil Kumar
80405103010
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Certificate
This is certified that the report file on ECG (electro cardio graph) has been completed by
Sunil Kumar80405103010
This file includes construction & working of ECG machine, which he did in 6 week training.
Mr. A.C.MONGRA H.O.D. (BME Deptt.)
ADESH INSTITUTE OF ENGG. & TECHNOLOGY, FARIDKOT
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Introduction
The electrocardiogram (ECG or EKG) is a diagnostic tool that measures and
records the electrical activity of the heart in exquisite detail. Interpretation of these
details allows diagnosis of a wide range of heart conditions. These conditions can
vary from minor to life threatening.
The term electrocardiogram was introduced by Willem Einthoven in 1893 at a
meeting of the Dutch Medical Society. In 1924, Einthoven received the Nobel
Prize for his life's work in developing the ECG.
The ECG has evolved over the years.
The standard 12-lead ECG that is used throughout the world was introduced
in 1942.
It is called a 12-lead ECG because it examines the electrical activity of the
heart from 12 points of view.
This is necessary because no single point (or even 2 or 3 points of view)
provides a complete picture of what is going on.
To fully understand how an ECG reveals useful information about the
condition of your heart requires a basic understanding of the anatomy (that
is, the structure) and physiology (that is, the function) of the heart.
Basic Anatomy of the Heart
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
The heart is a 4-chambered muscle whose function is to pump blood throughout
the body.
The heart is really 2 "half hearts," the right heart and the left heart, which
beat simultaneously.
Each of these 2 sides has 2 chambers: a smaller upper chamber called the
atrium (together, the 2 are called atria), and a larger lower chamber called
the ventricle.
Thus, the 4 chambers of the heart are called the right atrium, right ventricle,
left atrium, and left ventricle.
This sequence also represents the direction of blood flow through the heart.
The right atrium receives blood that has completed a tour around the body
and is depleted of oxygen and other nutrients. This blood returns via 2 large
veins: the superior vena cava returning blood from the head, neck, arms,
and upper portions of the chest, and the inferior vena cava returning blood
from the remainder of the body.
The right atrium pumps this blood into the right ventricle, which, a fraction
of a second later, pumps the blood into the blood vessels of the lungs.
The lungs serve 2 functions: to oxygenate the blood by exposing it to the air
you breathe in (which is 20% oxygen), and to eliminate the carbon dioxide
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
that has accumulated in the blood as a result of the body's many metabolic
functions.
Having passed through the lungs, the blood enters the left atrium, which
pumps it into the left ventricle.
The left ventricle then pumps the blood back into the circulatory system of
blood vessels (arteries and veins). The blood leaves the left ventricle via the
aorta, the largest artery in the body. Because the left ventricle has to exert
enough pressure to keep the blood moving throughout all the blood vessels
of the body, it is a powerful pump. It is the pressure generated by the left
ventricle that gets measured when you have your blood pressure checked.
The heart, like all tissues in the body, requires oxygen to function. Indeed, it is the
only muscle in the body that never rests. Thus, the heart has reserved for itself its
own blood supply.
This blood flows to the heart muscle through a group of arteries that begins
less than one-half inch from where the aorta begins. These are known as the
coronary arteries. These arteries deliver oxygen to both the heart muscle
and the nerves of the heart.
When something happens so that the flow of blood through a coronary
artery gets interrupted, then the part of the heart muscle supplied by that
artery begins to die. This is called coronary heart disease, or coronary artery
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
disease. If this condition is not stopped, the heart itself starts to lose its
strength to pump blood, a condition known as heart failure.
When the interruption of coronary blood flow lasts only a few minutes, the
symptoms are called angina, and there is no permanent damage to the heart.
When the interruption lasts longer, that part of the heart muscle dies. This is
referred to as a heart attack (myocardial infarction).
Nerves of the heart: The heart's function is so important to the body that it has its
own electrical system to keep it running independently of the rest of the body's
nervous system.
Even in cases of severe brain damage, the heart often beats normally.
An extensive network of nerves runs throughout all 4 chambers of the heart.
Electrical impulses course through these nerves to trigger the chambers to
contract with perfectly synchronized timing much like the distributor and
spark plugs of a car make sure that an engine's pistons fire in the right
sequence.
The ECG records this electrical activity and depicts it as a series of graph-
like tracings, or waves. The shapes and frequencies of these tracings reveal
abnormalities in the heart's anatomy or function.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Basics of ECG
ECG Electrodes
Skin Preparation:
Clean with an alcohol wipe if necessary. If the patients are very hairy – shave the
electrode areas.
ECG standard leads
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
There are three of these leads, I, II and III.
Lead I: is between the right arm and left arm electrodes, the left arm being positive.
Lead II: is between the right arm and left leg electrodes, the left leg being positive.
Lead III: is between the left arm and left leg electrodes, the left leg
again being positive.
Chest Electrode Placement
V1: Fourth intercostal space to the right of the sternum.
V2: Fourth intercostal space to the Left of the sternum.
V3: Directly between leads V2 and V4.
V4: Fifth intercostal space at midclavicular line.
V5: Level with V4 at left anterior axillary line.
V6: Level with V5 at left midaxillary line. (Directly under the midpoint of the armpit)
Chest Leads
V1 & V2
V3 & V4
V5 & V6
View
Right Ventricle
Septum/Lateral Left Ventricle
Anterior/Lateral Left Ventricle
The ECG records the electrical activity that results when the heart muscle cells in the
atria and ventricles contract.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Atrial contractions show up as the P wave.
Ventricular contractions show as a series known as the QRS complex.
The third and last common wave in an ECG is the T wave. This is the electrical
activity produced when the ventricles are recharging for the next contraction
(repolarizing).
Interestingly, the letters P, Q, R, S, and T are not abbreviations for any actual
words but were chosen many years ago for their position in the middle of the
alphabet.
The electrical activity results in P, QRS, and T waves that are of different sizes
and shapes. When viewed from different leads, these waves can show a wide
range of abnormalities of both the electrical conduction system and the muscle
tissue of the hearts 4 pumping chambers.
ECG Interpretation
The graph paper that the ECG records on is standardised to run at 25mm/second, and is
marked at 1 second intervals on the top and bottom. The horizontal axis correlates the
length of each electrical event with its duration in time. Each small block (defined by
lighter lines) on the horizontal axis represents 0.04 seconds. Five small blocks (shown by
heavy lines) is a large block, and represents 0.20 seconds.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Duration of a waveform, segment, or interval is determined by counting the blocks from
the beginning to the end of the wave, segment, or interval.
P-Wave: represents atrial depolarization - the time necessary for an electrical impulse
from the sinoatrial (SA) node to spread throughout the atrial musculature.
Location: Precedes QRS complex
Amplitude: Should not exceed 2 to 2.5 mm in height Duration: 0.06 to 0.11
seconds
P-R Interval: represents the time it takes an impulse to travel from the atria through the
AV node, bundle of His, and bundle branches to the Purkinje fibres.
Location: Extends from the beginning of the P wave to the beginning of the QRS
complex
Duration: 0.12 to 0.20 seconds.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
QRS Complex: represents ventricular depolarisation. The QRS complex consists of 3
waves: the Q wave, the R wave, and the S wave.
The Q wave is always located at the beginning of the QRS complex.
It may or may not always be present.
The R wave is always the first positive deflection.
The S wave, the negative deflection, follows the R wave
Location: Follows the P-R interval
Amplitude: Normal values vary with age and sex
Duration: No longer than 0.10 seconds
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Q-T Interval: represents the time necessary for ventricular depolarization and
repolarization.
Location: Extends from the beginning of the QRS complex to the end of the T
wave
(includes the QRS complex, S-T segment, and the T wave)
Duration: Varies according to age, sex, and heart rate
T Wave: represents the repolarization of the ventricles. On rare occasions, a U wave can
be seen following the T wave. The U wave reflects the repolarization of the His-Purkinje
fibres.
Location: Follows the S wave and the S-T segment
Amplitude: 5mm or less in standard leads I, II, and III; 10mm or less in precordial
leads V1-V6.
Duration: Not usually measured
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
S-T Segment: represents the end of the ventricular depolarization and the beginning of
ventricular repolarization.
Location: Extends from the end of the S wave to the beginning of the T wave
Duration: Not usually measured
The ECG and Myocardial Infarction
During an MI, the ECG goes through a series of abnormalities. The initial abnormality is
called a hyperacute T wave. This is a T wave that is taller and more pointed than the
normal T wave.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Hyperacute T Wave
The abnormality lasts for a very short time, and then elevation of the ST segment occurs.
This is the hallmark abnormality of an acute MI. It occurs when the heart muscle is being
injured by a lack of blood flow and oxygen and is also called a current of injury.
An ECG can not only tell you if an MI is present but can also show the approximate
location of the heart attack, and often which artery is involved. When the ECG
abnormalities mentioned above occur, then the MI can be localized to a certain region of
the heart. For example, see the table below:
ECG leads Location of MI Coronary Artery
II, III, aVF Inferior MI Right Coronary Artery
V1-V4 Anterior or Anteroseptal MI Left Anterior Descending Artery
V5-V6, I,aVL Lateral MI Left Circumflex Artery
ST depression in V1, V2 Posterior MI Left Circumflex Artery or Right Coronary Artery
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Circuit Diagram
Design Considerations
TI's new ADS1298 provides eight channels of PGA plus separate 24-bit delta-sigma
ADCs, a Wilson center terminal, the augmented Goldberger terminals and their
amplifiers, provide for a full, standard 12-lead ECG integrated analog front end. The
ADS1298 reduces component count and power consumption by up to 95 percent as
compared to discrete implementations, with a power efficiency of 1 mW/channel, while
allowing customers to achieve the highest levels of diagnostic accuracy
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
ECG System Functionality and Evolution
Basic functions of an ECG machine include ECG waveform display, either through LCD
screen or printed paper media, and heart rhythm indication as well as simple user
interface through buttons. More features, such as patient record storage through
convenient media, wireless/wired transfer and 2D/3D display on large LCD screen with
touch screen capabilities, are required in more and more ECG products. Multiple levels
of diagnostic capabilities are also assisting doctors and people without specific ECG
trainings to understand ECG patterns and their indication of a certain heart condition.
After the ECG signal is captured and digitized, it will be sent for display and analysis,
which involves further signal processing.
Signal Acquisition challenges:
Measurement of the ECG signal gets challenging due to the presence of the large
DC offset and various interference signals. This potential can be up to 300mV for
a typical electrode. The interference signals include the 50-/60-Hz interference
from the power supplies, motion artifacts due to patient movement, radio
frequency interference from electro-surgery equipments, defibrillation pulses,
pace maker pulses, other monitoring equipment, etc.
Depending on the end equipment, different accuracies will be needed in an ECG:
o Standard monitoring needs frequencies between 0.05-30 Hz
o Diagnostic monitoring needs frequencies from 0.05-1000 Hz
Some of the 50Hz/60Hz common mode interference can be cancelled with a high-
input-impedance instrumentation amplifier (INA), which removes the AC line
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
noise common to both inputs. To further reject line power noise, the signal is
inverted and driven back into the patient through the right leg by an amplifier.
Only a few micro amps or less are required to achieve significant CMR
improvement and stay within the UL544 limit. In addition, 50/60Hz digital notch
filters are used to reduce this interference further.
Analog front end options:
Optimizing the power consumption and the PCB area of the analog front end is
critical for portable ECG's. Due to technological advancements, there are now
several front end options:
o Using a low resolution ADC (needs all filters)
o Using a high resolution ADC (needs fewer filters)
o Using a sigma-delta ADC (needs no filters, no amplifier aside from INA,
no DC offset)
o Using a sequential Vs simultaneous sampling approach.
When a low resolution (16 bit) ADC is used, the signal needs to be gained up
significantly (typically 100x - 200x) to achieve the necessary resolution. When a
high resolution (24bit) sigma delta ADC is used, the signal needs a modest gain of
4 - 5x. Hence the second gain stage and the circuitry needed to eliminate the DC
offset can be removed. This leads to an overall reduction in area and cost. Also
the delta sigma approach preserves the entire frequency content of the signal and
gives abundant flexibility for digital post processing.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
With a sequential approach the individual channels creating the leads of an ECG
are multiplexed to one ADC. This way there is a definite skew between adjacent
channels. With the simultaneous sampling approach, a dedicated ADC is used for
each channel and hence there is no skew introduced between channels.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
Working of ECG
The ECG works mostly by detecting and amplifying the tiny electrical changes on the
skin that are caused when the heart muscle "depolarises" during each heart beat. At rest,
each heart muscle cell has a charge across its outer wall, or cell membrane. Reducing this
charge towards zero is called de-polarisation, which activates the mechanisms in the cell
that cause it to contract. During each heartbeat a healthy heart will have an orderly
progression of a wave of depolarisation that is triggered by the cells in the sinoatrial
node, spreads out through the atrium, passes through "intrinsic conduction pathways" and
then spreads all over the ventricles. This is detected as tiny rises and falls in the voltage
between two electrodes placed either side of the heart which is displayed as a wavy line
either on a screen or on paper. This display indicates the overall rhythm of the heart and
weaknesses in different parts of the heart muscle.
Usually more than 2 electrodes are used and they can be combined into a number of pairs
(For example: Left arm (LA), right arm (RA) and left leg (LL) electrodes form the pairs:
LA+RA, LA+LL, RA+LL). The output from each pair is known as a lead. Each lead is
said to look at the heart from a different angle. Different types of ECGs can be referred to
by the number of leads that are recorded, for example 3-lead, 5-lead or 12-lead ECGs
(sometimes simply "a 12-lead"). A 12-lead ECG is one in which 12 different electrical
signals are recorded at approximately the same time and will often be used as a one-off
recording of an ECG, typically printed out as a paper copy. 3- and 5-lead ECGs tend to
be monitored continuously and viewed only on the screen of an appropriate monitoring
device, for example during an operation or whilst being transported in an ambulance.
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
There may, or may not be any permanent record of a 3- or 5-lead ECG depending on the
equipment used.
It is the best way to measure and diagnose abnormal rhythms of the heart, [2] particularly
abnormal rhythms caused by damage to the conductive tissue that carries electrical
signals, or abnormal rhythms caused by electrolyte imbalances.[3] In a myocardial
infarction (MI), the ECG can identify if the heart muscle has been damaged in specific
areas, though not all areas of the heart are covered.[4] The ECG cannot reliably measure
the pumping ability of the heart, for which ultrasound-based (echocardiography) or
Sunil Kumar80405103010
Cardea Biomedical Labs New Delhi
nuclear medicine tests are used. It is possible to be in cardiac arrest with a normal ECG
signal (a condition known as pulseless electrical activity).
Sunil Kumar80405103010