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ECG & CARDIAC CYCLE

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by

DR NISA

on 8 January 2018

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Transcript of ECG & CARDIAC CYCLE

Electro = electric, cardio = heart, gram = recording
Records electrical events of the heart
Give information on the cardiac impulse
Origin
Pattern of spread
Rate of spread
Pacemaker potential generated by heart, can be detected by electrodes placed on the surface of the body
Electrocardiograph – machine to record ECG
Principle of ECG
ELECTROCARDIOGRAM & CARDIAC CYCLE
Dr Nik Aloesnisa bt Nik Mohd Alwi
MD; MMedSc (Physiology)

ELECTRCARDIOGRAM (ECG)
ECG paper
Recorded on standard paper with vertical & horizontal lines
Every 5th line is a thicker line
Recording the ECG
Explain the principles of electrocardiogram (ECG)

Define and explain cardiac cycle and heart sounds

Perform ECG and explain the differences between abnormal and normal pattern heart rhythm
OBJECTIVES
ELECTROCARDIOGRAM
ELECTROCARDIOGRAM
Describe the principles of ECG
Analyse & interpret the ECG
Identification of waves, intervals & segments
Calculation of the heart rate
Comment on the rhythm
DOES NOT GIVE INFORMATION ON
Contraction
Blood flow
Pressure within heart
The information is on ELECTRICAL and NOT MECHANICAL
Flow of an electrical current can be detected by a galvanometer
A & B - recording depolarisation waves

C & D - recording repolarisation waves
Positive waves
(Upward deflection)
A wave of depolarisation spreading towards the +ve pole
Negative wave
(Downward deflection)
A wave of depolarisation spreading away the +ve pole
Negative waves (Downward deflection)
A wave of repolarisation spreading towards +ve pole
Positive waves
(Upward defelction)
A wave of repolarisation spreading away +ve pole
Using electrodes - electrical activity of the heart can be recorded by placed the electrodes on the surface of the body - activity is conducted to all parts of the body through body fluids
Greater the current = greater the deflection of the needle = higher the amplitude of wave

Current flows for a longer time = the needle will be keep deflected longer = duration of the wave will be greater
The electrical activity of the heart is recorded with many pairs electrodes

By placing electrodes in several different positions in relation to the heart, we can get a ‘view’ of the heart from several different angles
Standard ECG - 12 pairs of electrodes.
Each such pair is called “LEAD”
Placement of electrodes is different in each lead – the amplitude & direction (+ve & -ve ) of waves recorded by each lead - different with each other
6 limbs leads
The electrodes are placed in the limbs; R arm, L arm & L leg
3 standard limb leads
+ve electrode one 1 limb & -ve electrode on another
3 augmented limb leads
+ve electrode on 1 limb & the electrodes on the other 2 limbs connected to the -ve
6 chest (ventricular) leads
The +ve electrodes are placed on the precordium
Placed on diferent positions & the electrodes on the 3 limbs connected to the -ve
Another electrode is attached to the R leg & earthed – not take part in recording
6 limb leads
3 standard limb leads (bipolar)
Lead I (+LA, -RA)
Lead II (+LF, -RA)
Lead III (+LF, -LA)
3 augmented limb leads (unipolar)
aVR (+RA)
aVL (+LA)
aVF (+LF)

6 chest (ventricular) leads
LEAD AXIS
An imaginary line joining the position of the –ve & +ve electrode of any lead is the axis of that lead
Lead I – axis is the joining the L & R shoulder
Lead II - axis is the joining the R shoulder & L leg
Lead III - axis is the joining the L shoulder & L leg

CARDIAC CYCLE
Cardiac events that occur from the beginning of one cardiac impulse to the beginning of the next
These events occur repeatedly in cyclical fashion
Electrical events
Mechanical events
Contraction
Blood flow
Pressure changes
Valve movements
Thank You
Identify all the waves, interval & segment
Full transcript