Download Electrocardiographs ECG

Electrocardiographs
ECG
OUTLINES :
 Introducing what is meant by Biopotential
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signals.
what is Electrocardiograph (ECG).
The conduction system.
The standard Lead system.
The ECG machine Construction.
Introduction to
Biopotential Signals
I
Electrocardiograph (ECG).
I
 The ECG is a graph showing the electrical activity due
to the systole and diastole of the heart muscle
 Which Records :
1-Amount of electrical activity of the heart.
2-The time required for the electrical activity to travel
through the heart .
3-The rate and rhythm of the heart.
 The heart acts as a blood pump.
 Heart contracts generating action potential.
 This potential creates electrical currents that spread
from the heart throughout the body.
 The spreading electrical currents create potentials
differences which can be detected through surface
electrodes
 The waveform produced is called the electrocardiogram
(ECG)
Electrocardiogram (ECG)
 Is a recording of electrical activity of heart conducted through
ions in body to surface
13-60
ECG Graph Paper
• Runs at a paper speed of 25 mm/sec
• Each small block of ECG paper is 1 mm2
• At a paper speed of 25 mm/s, one small block equals 0.04 s
• Five small blocks make up 1 large block which translates into
0.20 s (200 msec)
• Hence, there are 5 large blocks per second
• Voltage: 1 mm = 0.1 mV between each individual block vertically
(SA node)
(AV node)
Normal conduction pathway:
SA node -> atrial muscle -> AV node -> bundle of His -> Left
and Right Bundle Branches -> Ventricular muscle
Recording of the ECG:
Leads used:
• Limb leads are I, II, II.
• Each of the leads are bipolar; i.e., it requires two sensors on the skin to
make a lead.
•
If one connects a line between two sensors, one has a vector.
•
There will be a positive end at one electrode and negative at the other.
• The positioning for leads I, II, and
• III were first given by Einthoven.
• Form the basis of Einthoven’s triangle.
Types of ECG Recordings
 Bipolar leads record voltage
between electrodes placed
on wrists & legs (right leg is
ground)
 Lead I records between right
arm & left arm
 Lead II: right arm & left leg
 Lead III: left arm & left leg
13-61
ECG
 3 distinct waves are
produced during cardiac
cycle
 P wave caused by atrial
depolarization
 QRS complex caused by
ventricular depolarization
 T wave results from
ventricular repolarization
13-63
Normal ECG Waveform
ECG Readout devices
1- Medical Oscilloscope: vertical output is
severely limited.
 CRT persistence is very long .
 ECG use a horizontal sweep speed 25 mm/s.
2- strip chart recorder (speed 25 mm/s) and has
a grid pattern that is 50 mm wide.
The small grid are 1 mm apart.
The vertical scale is calibrated at 0.1 mV/mm