ECG Project Report

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 Kumar 80405103010


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



Certificate This is certified that the report file on ECG (electro cardio graph) has been completed by Sunil Kumar 80405103010 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



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.

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It is called a 12-lead ECG because it examines the electrical activity of the heart from 12 points of view.

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This is necessary because no single point (or even 2 or 3 points of view) provides a complete picture of what is going on.

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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 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.

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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.

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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.

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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.


Cardea Biomedical Labs New Delhi •

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 that has accumulated in the blood as a result of the body's many metabolic functions.

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Having passed through the lungs, the blood enters the left atrium, which pumps it into the left ventricle.

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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 disease. If this condition is not stopped, the heart itself starts to lose its strength to pump blood, a condition known as heart failure.

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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.

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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 graphlike tracings, or waves. The shapes and frequencies of these tracings reveal abnormalities in the heart's anatomy or function.



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 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)


Cardea Biomedical Labs New Delhi Chest Leads

View

V1 & V2

Right Ventricle

V3 & V4

Septum/Lateral Left Ventricle

V5 & V6

Anterior/Lateral Left Ventricle

The ECG records the electrical activity that results when the heart muscle cells in the atria and ventricles contract. •

Atrial contractions show up as the P wave.

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Ventricular contractions show as a series known as the QRS complex.

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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).

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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.

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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


Cardea Biomedical Labs New Delhi 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.

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.

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



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



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.



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

ST depression in V1, V2 Posterior MI

Circuit Diagram


Left Circumflex Artery Left Circumflex Artery or Right Coronary Artery


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

ECG System Functionality and Evolution


Cardea Biomedical Labs New Delhi 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.

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Depending on the end equipment, different accuracies will be needed in an ECG: o

Standard monitoring needs frequencies between 0.05-30 Hz

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Diagnostic monitoring needs frequencies from 0.05-1000 Hz

Some of the 50Hz/60Hz common mode interference can be cancelled with a highinput-impedance instrumentation amplifier (INA), which removes the AC line noise common to both inputs. To further reject line power noise, the signal is


Cardea Biomedical Labs New Delhi 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)

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Using a high resolution ADC (needs fewer filters)

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Using a sigma-delta ADC (needs no filters, no amplifier aside from INA, no DC offset)

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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.

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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


Cardea Biomedical Labs New Delhi channels. With the simultaneous sampling approach, a dedicated ADC is used for each channel and hence there is no skew introduced between channels.

Working of ECG Sunil Kumar 80405103010

Cardea Biomedical Labs New Delhi 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. There may, or may not be any permanent record of a 3- or 5-lead ECG depending on the equipment used. Sunil Kumar 80405103010


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 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).




ECG Project Report

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