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Also Known As: '''''ECG'''''
Also Known As: '''''ECG'''''
'''The colour coding system:'''
'''The colour coding system:'''
:<font color = "yellow">'''Yellow </font color>(positive): Left forelimb'''
<font color = "yellow">Yellow (positive): Left forelimb
:<font color = "red">'''Red </font color>(negative): Right forelimb'''
:<font color = "green">'''Green</font color>: Left hindlimb'''
<font color = "red">Red (negative): Right forelimb
:'''Black: Right hindlimb'''
<font color = "green">Green: Left hindlimb<font color = "black">
'''Black: Right hindlimb'''
The ECG should be recorded in a '''calm and quiet environment'''. The patient should be kept as '''still and relaxed''' as possible as '''muscle tremors and movement''' can cause '''artifacts''' on the trace. In horses the ECG is recorded '''standing'''. Dogs should be placed in '''right lateral recumbency''' but positioning in a cat is less important. The cables should be positioned so that they do not drape over the animals chest as they can cause '''respiratory movement artifact'''. Electrical activity can cause interference on the ECG trace (known as '''50Hz interference'''). To prevent this it should be taken on an '''insulated surface''' away from fluorescent lighting, computers and other electrical equipment. A '''Holter''' ECG can be used in both small and large animal to record the electrical activity of the heart over 24 hours or during exercise.
The ECG should be recorded in a '''calm and quiet environment'''. The patient should be kept as '''still and relaxed''' as possible as '''muscle tremors and movement''' can cause '''artifacts''' on the trace. In horses the ECG is recorded '''standing'''. Dogs should be placed in '''right lateral recumbency''' but positioning in a cat is less important. The cables should be positioned so that they do not drape over the animals chest as they can cause '''respiratory movement artifact'''. Electrical activity can cause interference on the ECG trace (known as '''50Hz interference'''). To prevent this it should be taken on an '''insulated surface''' away from fluorescent lighting, computers and other electrical equipment. A '''Holter''' ECG can be used in both small and large animal to record the electrical activity of the heart over 24 hours or during exercise.
'''Chemical restraint''' should be '''avoided''' if at all possible as this changes the ECG.
'''Chemical restraint''' should be '''avoided''' if at all possible as this changes the ECG.
==Reading an ECG Trace==
==Reading an ECG Trace==
An ECG only supplies information about the '''electrical activity of the heart'''. It indicates the heart rate and rhythm and can be used to detect any arrhythmias but does not supply information about cardiac function. It is important to remember to '''treat the patient not the ECG'''!
An ECG only supplies information about the '''electrical activity of the heart'''. It indicates the heart rate and rhythm and can be used to detect any arrhythmias but does not supply information about cardiac function. It is important to remember to '''treat the patient not the ECG'''!
To interpret an ECG it is necessary to understand the path of depolarisation through the [[Category:Heart - Anatomy & Physiology|heart]]:
To interpret an ECG it is necessary to understand the path of depolarisation through the [[:Category:Heart - Anatomy & Physiology|heart]]:
The sino-atrial node depolarises spontaneously and this wave of depolarisation spreads through the atria. The impulse is then conducted through AV node slowly. Then it rapidly passes through the bundle of His and bundle branches, spreading through the ventricular myocardium. The myocardium then remains depolarised for a period before repolarising. This '''depolarisation and repolarisation are detected as potential differences on the skin surface - producing the classic shape of the ECG trace'''.
The sino-atrial node depolarises spontaneously and this wave of depolarisation spreads through the atria. The impulse is then conducted through AV node slowly. Then it rapidly passes through the bundle of His and bundle branches, spreading through the ventricular myocardium. The myocardium then remains depolarised for a period before repolarising. This '''depolarisation and repolarisation are detected as potential differences on the skin surface - producing the classic shape of the ECG trace'''.
'''(1) Instantaneous heart rate'''
'''(1) Instantaneous heart rate'''
:1500/R-R interval (25 mm/sec)
1500/R-R interval (25 mm/sec)
:3000/R-R interval (50 mm/sec)
3000/R-R interval (50 mm/sec)
'''(2) Number of R-R intervals in 6 seconds x 10'''
'''(2) Number of R-R intervals in 6 seconds x 10'''
Where multiple rhythms exist, the rate of all rhythms present should be calculated.
Where multiple rhythms exist, the rate of all rhythms present should be calculated.
A high heart rate may be due to [[Sinus Tachycardia|sinus tachycardia]], [[Supraventricular Tachycardia|supraventricular tachycardia]], [[Ventricular Tachycardia|ventricular tachycardia]] and [[Atrial Fibrillation & Atrial Flutter|atrial fibrillation]]. A slow heart rate may be caused by [[Sinus Bradycardias|sinus bradycardia]], [[Sinus Arrhythmias|sinus arrhythmia]], second or third degree [[Atrio-Ventricular Block|AV block]], [[Atrial Standstill|atrial standstill]] and [[Sinus Arrest & Sinus Block|sinus arrest]].
===='''What is the heart rhythm?'''====
===='''What is the heart rhythm?'''====
Sparks, AH & Caney, SMA (2005) '''Self-Assessment Colour Review Feline Medicine''' ''Manson''
Sparks, AH & Caney, SMA (2005) '''Self-Assessment Colour Review Feline Medicine''' ''Manson''
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[[Category:Monitoring Anaesthesia]]
[[Category:Monitoring Anaesthesia]]
[[Category: To Do - Siobhan Brade]]
[[Category:Clinical Techniques]]
[[Category:To Do - Manson review]]
[[Category:Expert Review]]