ECG Flashcards
What should you divide the number of small boxes by on an ECG to get the p-r interval?
3000 - 50 mm/s
1500 - 25 mm/s
What should you count for dysrrthymias?
Atrial rate and ventricular rate
What does a wide and bizarre QRS complex indicate?
Ventricular origin
Conduction disturbance in the purkinje fibres - eg: fibrosis
What would you suspect if a t wave is tall and spiky or symmetrical?
Blood gas disturbance or electrolyte imbalance
What does slurring of the QRS complex into the T wave indicate?
Myocardial hypoxia
Ventricular enlargement
What does a prolonged p wave indicate?
P mitrale - left atrial enlargement
What does a tall P wave indicate ?
Right atrial enlargement?
What does a tall QRS complex indicate?
Left ventricular enlargement
What does a prolonged QRS complex indicate?
Left ventricular enlargement and hypertrophy
Sinus arrhythmia
R-R interval rhythmically decreases (inspiration) and lengthens (expiration)
Due to high resting vagal tone
Sinus arrest
No electrical activity for a period preceding two normal r-r intervals
Due to high vagal tone in brachycephalics
1st degree Atrioventricular block
P: QRS ratio remains 1:1
P-R interval is longer than normal for the species
May be due to high vagal tone or digoxin
2nd degree AV block
Some non-conducted P waves
QRS complex normal
Mobitz type 1 - variable P-R interval - physiological
Maobitz type 2 - fixed P-R interval - pathological
3rd degree AV block
P waves are not associated to the QRS
Ventricular escape complexes
Atrial fibrillation
Oscillating baseline
Fast ventricular rate
Normal QRS complexes but chaotic rhythm
Supra ventricular tachycardia
Premature complex occurs - normal QRS but will no preceding p wave and premature in the rhythm
Ventricular tachycardia
Wide and bizarre QRS complexes with opposite t wave
Positive in lead 1 and 2 with negative t waves - origin right ventricle
Negative in lead 1 and 2 with positive t waves - origin in left ventricle
Ventricular fibrillation
Complete loss of co-ordinated ventricular depolarisation
Hyperkalaemia
Sino ventricular rhythm
No discernible p waves
Tall and spikey t waves
Normal QRS
What arrhythmia is normal in the dog but not in the cat? And what should you investigate?
Sinus arrhythmia
- feline asthma
- diaphragmatic hernia
How can you diagnose sinus arrest?
Atropine - abolishes the arrest
How does sick sinus syndrome present?
WHWT
No p waves for a time= periods of sinus arrest
Junctional escape complexes
Tx: pacemaker implantation
How long a period of arrest will cause syncope?
10 seconds
What does ventricular tachycardia with polymorphic QRS complexes indicate?
Multiple ectopic foci
What systemic conditions affect the heart conducting system, therefore cause ventricular premature complexes?
GDV Splenectomy / splenic lesions eg: haemangiosarcoma Sepsis Pancreatitis Pyometra Thoracic trauma CNS lesions
What is the aetiology of AV block?
Physiological - high vagal tone
Pathological - fibrosis of the AVN
What might causes a short ‘damped’ QRS complex?
Large breed
Fat
Pleural effusion
Thoracic mass
How does a left bundle branch block appear on an ECG?
Normal P:QRS ratio
Tall wide QRS complex with opposing t wave
QRS duration longer than 0.08s
MEA normal
How does a rig bundle branch block appear on an ecg?
Normal P:QRS ratio Deep, wide S waves Negative QRS T waves occur in the opposite direction Right axis deviation
How does a left anterior fasicular block appear on an ecg?
Positive QRS complex in lead I
Negative S wave on lead II and III
Normal QRS duration
Left axis deviation
Seen in feline HCM
What factors can cause a plonked QT interval?
Hypocalcaemia
Hypothermia
Dehydrated
What causes ST segment elevation?
Pericardial effusion
How should you investigate episodes of syncope?
Holter monitor - 24h ECG Blood pressure check Blood tests for metabolic status Check glucose - insulinoma can cause Check for brain tumours Underlying disease
How does a wandering pacemaker appear on an ECG and what causes it?
Variable p wave morphology
High vagal tone
What does a tall, spikey S wave indicate?
Right ventricular enlargement
What diseases increase vagal tone and may lead to sinus arrhythmias?
Respiratory disease Intra-cranial disease Intra-ocular pressure Pleural disease Thoracic masses Abdominal disease
What affects the MEA?
Bundle branch blocks
Ventricular enlargement
How can you tell the location of a bundle branch block? And how can you tell the location of the origin of VPC?
Left bundle branch block - positive
Right bundle branch block - negative
Opposite way around for VPCs
Right VPC - origin in the right hand side
Left VPC - origin in the left hand side
How can you tell the origin of a supra ventricular premature complex from the presence / absence of p waves?
P wave associated - sinus
P waves of different morphology - atrial eg: fibrillation line
What is the normal MEA for a dog?
40-100 degrees
What is the normal MEA for a cat?
0-160 degrees
