The document provides information about various medical devices used to record electrical activity in the body, including electrocardiograms (ECGs), electroencephalograms, electromyograms, and electrooculograms. It then discusses the history and development of the ECG, including early experiments in the late 18th century. The document outlines the basic anatomy and function of the heart, including the components that receive and pump blood. It describes the electrical conduction system of the heart and the patterns of excitation. The document explains the various waves that make up the ECG, including the P, QRS, T waves, and relates them to electrical and muscular events in the heart. It provides diagrams of heart anatomy and the instrumentation used

1. Department of Biomedical Engineering
Faculty of Engineering
University of Isfahan
Seyed Yahya Moradi s.yahyamoradi@mehr.ui.ac.ir
2013/5/10

2. Medical Devices
Electro cardio [kardio] gram [graph]
Is a tool that is used to assess the electrical and muscular functions of the heart.
Electro encephalo gram
Is a tool that measures and records the electrical activity of the brain.
Electro myo gram
Is a tool that is used to record the electrical activity of the muscles.
Electro oculo /nystagmo gram
Is a tool that measures normal eye movement and involuntary rapid eye movements.
1

3. History of ECG
1786 : Luigi Aloisio Galvani
On September 20th 1786 he wrote "I had dissected and prepared a frog in
the usual way and while I was attending to something else I laid it on a table
on which stood an electrical machine at some distance from its conductor
and was separated from it by a considerable space. Suddenly when one of
the persons present in there lightly touched the inner crural nerves of the
frog with the point of a scalpel, all the muscles of the legs seemed to
contract again and again as if they were affected by powerful cramps.“
2

4. 1856 : Rudolph von Koelliker and Heinrich Muller
They confirmed that an electrical current accompanies each heart beat by applying
a galvanometer to the base and apex of an exposed ventricle. They also applied a
nerve-muscle preparation similar to Matteucci's, to the ventricle and observed that
a twitch of the muscle occurred just prior to ventricular systole and also a much
smaller twitch after systole.
3

5. 1887 : Augustus Desiré Waller
1901-1905 : Willem Einthoven
By 1901 Willem Einthoven had completed work on the string galvanometer. String
galvanometers had been used to amplify signals across long-distance submarine
cables but his device was much more sensitive. The device consisted of a very thin
filament of conductive wire passing between very strong electromagnets.When a
current passed through the filament, the string moved because of the change in the
electromagnetic field. The electrical activity of the heart was recorded on
photographic paper from a light passing through the string The early machine
needed water for cooling because of the electromagnetic field , required 5 people
to operate, and weighed 600 pounds.In addition, the patient was required to keep
a leg and an arm in a bucket of water.
He was the first to use
a mercury capillary
electrometer For
recording a human
electrocardiogram .
4

6. 5

7. Basic Anatomy of the Heart
About the heart:
The heart is the hardest working muscle in the human body.
The heart weighs between 7 and 15 ounces (200 to 425 grams)
and is a little larger than the size of your fist. By the end of a
long life, a person's heart may have beat (expanded and
contracted) more than 3.5 billion times. In fact, each day, the
average heart beats 100,000 times, pumping about 2,000
gallons (7,571 liters) of blood. Your heart is located between
your lungs in the middle of your chest, behind and slightly to
the left of your breastbone (sternum)
The way a normal heart works :
The cardiovascular system, composed of the heart and
blood vessels, is responsible for circulating blood
throughout your body to supply the tissues with oxygen
and nutrients. The heart is the muscle that pumps blood
filled with oxygen and nutrients through the blood
vessels to the body tissues.
6

8. Components of heart
That receive blood from the body and pump out blood to it:
The atria receive blood coming back to the heart.
The ventricles pump the blood out of the heart.
Which compose a network of arteries and veins that carry blood throughout the body:
Arteries transport blood from the heart to the body tissues.
Veins carry blood back to the heart.
To prevent backward flow of blood:
Each valve is designed to allow the forward flow of blood and prevent backward flow.
Which stimulates contraction of the heart muscle.
7

9. 8

10. RealtimeMRIofThorax
9

11. The Heart Valves
Function of Heart Valves
■ Fibrous connective tissue prevents
enlargement of valve
openings and anchors valve flaps.
■ Valve closure prevents backflow of
blood during and aftercontraction
The tricuspid valve regulates blood flow between the right atrium and right ventricle.
The pulmonary valve controls blood flow from the right ventricle into the pulmonary
arteries, which carry blood to your lungs to pick up oxygen.
The mitral valve lets oxygen-rich blood from your lungs pass from the left atrium into
the left ventricle.
The aortic valve opens the way for oxygen-rich blood to pass from the left ventricle into
the aorta, your body's largest artery, where it is delivered to the rest of your body.
Four types of valves regulate blood
flow through your heart:
10

12. 11

13. Dominant pacemaker of the heart, located in
upper portion of right atrium.
Direct electrical impulses between SA and AV
nodes.
Part of AV junctional tissue. Slows Conduction
before impulses reach ventricles.
Transmits impulses to bundle branches.
Located below AV node
Conducts impulses that lead to left ventricle
Conducts impulses that lead to right ventricle
which spreads impulses Rapidly throughout
ventricular walls.Located at terminals of
bundle branches.
Structure ,Function and Location of ESH
12

14. Pattern of Excitation in the heart
13

15. The P Wave
The first wave (p wave) represents atrial depolarisation. When the valves
between the atria and ventricles open, 70% of the blood in the atria falls
through with the aid of gravity, but mainly due to suction caused by the
ventricles as they expand.
Atrial contraction is required only for the final 30% and therefore a relatively
small muscle mass is required and only a relatively small amount of voltage is
needed to contract the atria.
14

16. After the first wave there follows a short period where the line is flat. This is
the point at which the stimulus is delayed in the bundle of His to allow the
atria enough time to pump all the blood into the ventricles.
As the ventricles fill, the growing pressure causes the valves between the
atria and ventricles to close. At this point the electrical stimulus passes from
the bundle of His into the bundle branches and Purkinje fibres. The amount
of electrical energy generated is recorded as a complex of 3 waves known
collectively as the QRS complex. Measuring the waves vertically shows
voltage. More voltage is required to cause ventricular contraction and
therefore the wave is much bigger
it is possible to break down the QRS complex into 3 distinct waves:
 Q wave representing septal depolarisation
 R wave representing ventricular depolarisation
 S wave representing depolarisation of the Purkinje fibres.
The QRS Complex
15

17. The Q Wave
The picture below shows a small negative wave immediately before the large
QRS complex. This is known as a Q wave and represents depolarisation in the
septum.
Whilst the electrical stimulus passes through the bundle of His, and before it
separates down the two bundle branches, it starts to depolarise the septum
from left to right. This is only a small amount of conduction (hence the Q
wave is less than 2 small squares), and it travels in the opposite direction to
the main conduction (right to left) so the Q wave points in the opposite
direction to the large QRS complex.
16

18. The R Wave
The QRS complex is made up of three waves. These waves indicate the changing
direction of the electrical stimulus as it passes through the heart's conduction
system.
The largest wave in the QRS complex is the R wave
As you can see from the diagram, the R wave represents the electrical stimulus
as it passes through the main portion of the ventricular walls. The wall of the
ventricles are very thick due to the amount of work they have to do and,
consequently, more voltage is required. This is why the R wave is by far the
biggest wave generated during normal conduction.
17

19. The S Wave
You will also have seen a small negative wave following the large R wave.
This is known as an S wave and represents depolarisation in the Purkinje
fibres.
The S wave travels in the opposite direction to the large R wave because, as
can be seen on the earlier picture, the Purkinje fibres spread throughout the
ventricles from top to bottom and then back up through the walls of the
ventricles.
18

20. The T Wave
Both ventricles repolarise before the cycle repeats itself and
therefore a 3rd wave (t wave) is visible representing ventricular
repolarisation.
19

21. The ST Segment
There is a brief period between the end of the QRS complex and the beginning
of the T wave where there is no conduction and the line is flat. This is known
as the ST segment and it is a key indicator for both myocardial ischaemia and
necrosis if it goes up or down.
20

22. CARDIAC CYCLES
21

23. ECG paper
The output of an ECG recorder is a graph (or
sometimes several graphs, representing each of
the lead) with time represented on the x-axis
and voltage represented on the y-axis. A
dedicated ECG machine would usually print
onto graph paper which has a background
pattern of 1mm squares (often in red or green),
with bold divisions every 5 mm in both vertical
and horizontal directions.It is possible to change
the output of most ECG devices but it is standard
to represent each mV on the y axis as 1 cm and
each second as 25 mm on the x-axis (that is a
paper speed of 25 mm/s). Faster paper speeds
can be used, for example, to resolve finer detail
in the ECG. At a paper speed of 25 mm/s, one
small block of ECG paper translates into 40 ms.
Five small blocks make up one large block, which
translates into 200 ms. Hence, there are five
large blocks per second. A calibration signal may
be included with a record. A standard signal of
1 mV must move the stylus vertically 1 cm, that
is, two large squares on ECG paper.
22

24. ECG Bloke Diagram
23

25. Instrumentation Amplifier
AD524 ،AD521 ،AD625 ،AD624 ،AD620
An instrumentation amplifier is a type of differential amplifier that has been outfitted
with input buffer amplifiers, which eliminate the need for input impedance
matching and thus make the amplifier particularly suitable for use in measurement
and test equipment. Additional characteristics include very low DC offset, low drift,
low noise, very high open-loop gain, very high common-mode rejection ratio, and
very high input impedances
24

26. Filters
Low Pass Filter:
There are many types of low pass filter like Butterworth and Chebyshev
filters (in the project the Butterworth filter was used). Low pass filter used
to filter out signals at frequencies higher than the filters cut off frequency
which is required in the project (to reject frequencies higher than 100 Hz).
High Pass Filter:
A High Pass filter is a filter that passes high frequencies and attenuates low
frequencies. Also, high pass filters are useful to filter out the undesired low
frequency components from the main high frequency signals, they are
usually used in applications requiring the rejection of low frequency signals.
Notch Filter:
A notch filter is required to eliminate the 50Hz interference, this
interference comes from the power lines carrying this frequency in close
proximity to patient and equipment.
25

27. A microcontroller is an electronic device that
generally consists of a microprocessor, a memory unit in the form of random
access memory (RAM) and Read Only Memory (ROM), various timers and
input/output serial and parallel ports all integrated on a single chip. In some
advanced microcontroller systems, on chip ADC’s, DAC’s etc are also included.
examples of microcontrollers
26

28. ECG leads
Lead I : is connected to
the right arm and the
positive terminal to the
left arm.
Lead II : is connected
negative terminal of the
electrocardiograph which
connected to the right
arm and the positive
terminal to the left leg
and lead.
Lead III : is connected to
the left arm and the
positive terminal to the
left leg.
Limb leads
27

29. CHEST LEADS
4th Intercostal space to Septumright
of sternum
4th Intercostal space to Septumleft
of sternum
Directly between V2 and V4 Anterior
5th Intercostal space at Anteriorleft
midclavicular line
Level with V4 at left anterior Lateral axillary line
Level with V5 at left midaxillary line Lateral
28

30. ECG machine
29

31. 30

32. Main Board
31

33. Power
Supply
Board
32

34. Printer
33

35. Panel
34

36. ANY
QUESTIONS ?