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ECG Recording
Clinical Skills
ECG Recording
Dawn Lau, Spring 2011
ECG Recording
Learning Objectives
Learning Objectives
To learn how to record a full, detailed tracing of the electrical activity of the heart, using an ECG
(electrocardiograph) machine recorder;
That is, ‘How to perform a 12-lead ECG’
How to set up a continuous recording of the ECG ie cardiac monitoring
•
•
ECG rhythm strip
ECG tracing
ECG Recording
What is an ECG?
What is an ECG?
The electrocardiogram (ECG) is a record of the electrical conduction activity of the heart, and is
represented by waveforms which are formed by the net result of electrical vectors flowing
within the conduction system of the heart.
The waveform looks different in appearance depending on from which angle and plane one
‘looks’ at the heart.
His-Purkinje Conduction system
ECG Recording
What is an ECG?
What is an ECG?
The 12-lead ECG thus gives an ‘electrical map’ of the heart’s activity and crucially enables one to
identify cardiac conduction abnormalities and ischaemic heart disease.
ECG rhythm strip
using Lead II
ECG Recording
Standard ECG Calibration
Standard ECG Calibration
The ECG is recorded on to standard paper
travelling at a rate of 25 mm/s. The paper is
divided horizontally into:
• 1 small square = 1 mm wide =
0.04 s
• Each large square contains five
small squares in width
• 1 large square = 5 mm wide = 0.2 s
The electrical activity detected by the ECG machine is measured in millivolts. Machines are
calibrated so that a signal with an amplitude of 1 mV moves the recording stylus vertically 1 cm:
• 1 small vertical square = 0.1 mV = 1 mm
Hence, always look at bottom of any ECG to ensure the standard 25mm/s; 10mm/mV or
equivalent (or else you may find yourself misinterpreting the rate/sizes of waveforms!)
ECG Recording
How to do a 12-lead ECG
How to do a 12-lead ECG
 Equipment
 Preparation
 Procedure
Equipment: Take time to familiarise yourself with the machines and equipment
Watch how it’s done on the ward or cardiology investigations unit
ECG Recording
Preparation
Preparation
Patient
•
•
•
Patient position – comfortable on a
trolley/bed, about 45° incline
Expose chest and distal limbs
Consider shaving chest at locations of
ECG electrode placement
Machine
• The obvious, but ensure machine is
switched on and ECG grid paper is
fitted in.
• Check that speed and calibration
settings are set correctly (this is
usually ‘default’ on the ECG machine,
but be aware)
ECG Recording
Cardiac Monitoring
Cardiac Monitoring
Gives a ‘real-time’ ability to monitor cardiac electrical
activity
There are quite a variety of equipment to do just that,
although the basic aspects and features of each
equipment are similar. It’s helpful therefore to
familiarise yourself with a machine you come across on
the ward, and ask the Nurse to show how to use it on a
patient. This advice particularly holds great importance
with the defibrillator machine – know its dials and
buttons – in the event that you may eventually have to
operate it during a cardiac arrest.
A few of these equipments are shown here:
– Bedside monitoring and ECG electrode stickers
– Cardiac monitoring in the coronary care unit (CCU)
– Cardiac defibrillator machine
The ECG machine, besides a 12-lead ECG, can also be made to record a rhythm strip with a press of
the appropriate button.
ECG Recording
ECG rhythm strip
ECG rhythm strip
The ECG strip gives additional information to the 12-lead ECG. It gives a view from one lead and
its role, as the name suggests, is to produce a temporally longer recording of the ECG so as to
facilitate in the identification and monitoring of the abnormal rhythm.
This is particularly useful in:
• Profound bradycardia
• Profound tachycardia
• Real-time recording of a therapeutic/diagnostic intervention e.g. administration of i.v.
adenosine, or electrical cardioversion.
ECG Recording
Bedside Cardiac Monitoring
Bedside Cardiac Monitoring
Usually patients requiring cardiac monitoring are attached to a portable bedside 3-lead monitor.
The electrodes (with colours of electrodes shown) are placed in 3 spots:
• Right shoulder, Left shoulder and Left rib cage
R
shoulder
L
shoulder
L
ribcage
ECG Recording
Cardiac Defibrillator
Cardiac Defibrillator
You will have the opportunity (if not already) to learn the Advanced Life Support (ALS)
algorithms, which are beyond the realm of this module; however this picture shows a
commonly used defibrillator on a medical ward. Get familiar with it.
ECG Recording
Functions of the Cardiac Defibrillator Machine
Functions of the Cardiac Defibrillator Machine
This machine has combined functions:
• ECG display screen
• Defibrillator function
• Cardioversion function
• External pacing function for bradyarrythmias
The ECG display screen allows for ECG monitoring, using either leads or pads applied to the
anterior chest. The difference between ‘defibrillation’ and ‘cardioversion’ is dependant on the
type of the dysrhythmia and the level of compromise to the patient.
Defibrillation: electric current treatment for immediately life-threatening arrhythmias in which
the patient does not have a pulse e.g. VF and pulseless VT.
Cardioversion: process that aims to convert a tachy-arrhythmia back into sinus rhythm. Electrical
cardioversion is considered in these dysrhythmias with pulse which are haemodynamically
unstable (pharmacological means will take too long to act in these situations); or in elective
situations where pharmacological cardioversion has failed or unlikely to be successful.
ECG Recording
Functions of the Cardiac Defibrillator
Functions of the Cardiac Defibrillator
So, in ‘Sync’ mode, you will commonly experience a transient delay from the moment you press
the ‘Shock’ button to the moment the machine delivers the shock to the patient on the next R
wave.
In contrast, the defibrillator mode will deliver the shock the instant you press the ‘Shock’
button. The pulse-less life-threatening arrhythmias for which the defibrillator is indicated has no
need (and indeed is impossible in VF) for a synchronised shock.
ECG Recording
Practical Tips
Practical Tips
Accurate and consistent positioning of electrodes – so that serial ECGs can be compared
Good electrode-to-skin electrical contact:
• Chest wall should be clean and dry, so wipe off sweat; oil or grease with alcohol
wipes.
• May have to shave off chest hair in appropriate places as hair is a poor conductor of
electrical signal, and may also interfere with the sticking ability of electrodes.
A relaxed and comfortable patient – to minimise ‘noise’ and interference from skeletal
muscles/movements and optimise quality. Wait for the real-time tracing on the ECG machine
screen to look of good and consistent quality before pressing the ‘Print’ button.
Remember the speed and calibration settings are set correctly (this is usually ‘default’ on the
ECG machine, but be aware)
ECG Recording
Summary
Summary
It is a basic clinical skill to record a 12-lead ECG (electrocardiograph) using an ECG machine
recorder as well as to record a rhythm strip.
Familiarise yourself with the various machines which record cardiac monitoring: the bedside
monitor, the cardiac defibrillator machine, the ECG machine recorder.
The 12-lead ECG gives an ‘electrical map’ of the heart’s activity and crucially enables one to
identify cardiac conduction abnormalities, certain structural abnormalities and ischaemic heart
disease.
The ECG rhythm strip adds further information and is useful particularly in very slow or fast
heart rates, and records interventions to treat arrythmias.
ECG Recording
Resources & References
Resources & References
A mere selected few give clear background and excellent know-how on interpreting ECGs:
Hampton JR. (2008). The ECG made easy. (7th Ed) Churchill Livingstone.
Also by John R Hampton: The ECG in Practice (5th Ed); 150 ECG problems (3rd Ed). Churchill
Livingstone.
Morris F, Brady WJ, Camm J (Eds) (2008). ABC of clinical electrocardiography. (2nd Ed) Blackwell
Publishing/BMJ Books.
Longmore M et al (2010). Oxford Handbook of Clinical Medicine. (8th Ed) Oxford University
Press.
James S Fleming: Interpreting the Electrocardiogram (1979).
Resuscitation Council (UK) (2010). Resuscitation Guidelines. Downloaded at www.resus.org.uk
ECG Recording
Acknowledgements
Acknowledgements
Dr Zaheer Yousef, Consultant Cardiologist, UHW
Joshua Dimbylow, Medical E-learning Developer
Cardiac Investigations Department, University Hospital of Wales for the use of the ECG machine
Media Resources Team – Carl Rogers
Medical Photography; Amy Lake, Bolette Jones & team
B1 Cardiology Staff including Caroline and Sonia
http://www.patient.co.uk/doctor/Defibrillation-and-Cardioversion.htm
cardiology.ucsf.edu/ep/Imagesheart/normalecg.jpg
www.ctsnet.org/graphics/experts/Adult/cosav1.jpg
http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/resources/
ECG Recording
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