ECG

Question 1

What should you divide the number of small boxes by on an ECG to get the p-r interval?

Answer 1

3000 - 50 mm/s

1500 - 25 mm/s

Question 2

What should you count for dysrrthymias?

Answer 2

Atrial rate and ventricular rate

Question 3

What does a wide and bizarre QRS complex indicate?

Answer 3

Ventricular origin

Conduction disturbance in the purkinje fibres - eg: fibrosis

Question 4

What would you suspect if a t wave is tall and spiky or symmetrical?

Answer 4

Blood gas disturbance or electrolyte imbalance

Question 5

What does slurring of the QRS complex into the T wave indicate?

Answer 5

Myocardial hypoxia

Ventricular enlargement

Question 6

What does a prolonged p wave indicate?

Answer 6

P mitrale - left atrial enlargement

Question 7

What does a tall P wave indicate ?

Answer 7

Right atrial enlargement?

Question 8

What does a tall QRS complex indicate?

Answer 8

Left ventricular enlargement

Question 9

What does a prolonged QRS complex indicate?

Answer 9

Left ventricular enlargement and hypertrophy

Question 10

Sinus arrhythmia

Answer 10

R-R interval rhythmically decreases (inspiration) and lengthens (expiration)
Due to high resting vagal tone

Question 11

Sinus arrest

Answer 11

No electrical activity for a period preceding two normal r-r intervals
Due to high vagal tone in brachycephalics

Question 12

1st degree Atrioventricular block

Answer 12

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

Question 13

2nd degree AV block

Answer 13

Some non-conducted P waves
QRS complex normal

Mobitz type 1 - variable P-R interval - physiological
Maobitz type 2 - fixed P-R interval - pathological

Question 14

3rd degree AV block

Answer 14

P waves are not associated to the QRS

Ventricular escape complexes

Question 15

Atrial fibrillation

Answer 15

Oscillating baseline
Fast ventricular rate
Normal QRS complexes but chaotic rhythm

Question 16

Supra ventricular tachycardia

Answer 16

Premature complex occurs - normal QRS but will no preceding p wave and premature in the rhythm

Question 17

Ventricular tachycardia

Answer 17

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

Question 18

Ventricular fibrillation

Answer 18

Complete loss of co-ordinated ventricular depolarisation

Question 19

Hyperkalaemia

Answer 19

Sino ventricular rhythm
No discernible p waves
Tall and spikey t waves
Normal QRS

Question 20

What arrhythmia is normal in the dog but not in the cat? And what should you investigate?

Answer 20

Sinus arrhythmia

• feline asthma
• diaphragmatic hernia

Question 21

How can you diagnose sinus arrest?

Answer 21

Atropine - abolishes the arrest

Question 22

How does sick sinus syndrome present?

Answer 22

WHWT
No p waves for a time= periods of sinus arrest
Junctional escape complexes

Tx: pacemaker implantation

Question 23

How long a period of arrest will cause syncope?

Answer 23

10 seconds

Question 24

What does ventricular tachycardia with polymorphic QRS complexes indicate?

Answer 24

Multiple ectopic foci

Question 25

What systemic conditions affect the heart conducting system, therefore cause ventricular premature complexes?

Answer 25

GDV
Splenectomy / splenic lesions eg: haemangiosarcoma 
Sepsis
Pancreatitis 
Pyometra 
Thoracic trauma 
CNS lesions

Question 26

What is the aetiology of AV block?

Answer 26

Physiological - high vagal tone

Pathological - fibrosis of the AVN

Question 27

What might causes a short ‘damped’ QRS complex?

Answer 27

Large breed
Fat
Pleural effusion
Thoracic mass

Question 28

How does a left bundle branch block appear on an ECG?

Answer 28

Normal P:QRS ratio
Tall wide QRS complex with opposing t wave
QRS duration longer than 0.08s
MEA normal

Question 29

How does a rig bundle branch block appear on an ecg?

Answer 29

Normal P:QRS ratio
Deep, wide S waves 
Negative QRS
T waves occur in the opposite direction
Right axis deviation

Question 30

How does a left anterior fasicular block appear on an ecg?

Answer 30

Positive QRS complex in lead I
Negative S wave on lead II and III
Normal QRS duration
Left axis deviation

Seen in feline HCM

Question 31

What factors can cause a plonked QT interval?

Answer 31

Hypocalcaemia
Hypothermia
Dehydrated

Question 32

What causes ST segment elevation?

Answer 32

Pericardial effusion

Question 33

How should you investigate episodes of syncope?

Answer 33

Holter monitor - 24h ECG
Blood pressure check 
Blood tests for metabolic status
Check glucose - insulinoma can cause
Check for brain tumours 
Underlying disease

Question 34

How does a wandering pacemaker appear on an ECG and what causes it?

Answer 34

Variable p wave morphology

High vagal tone

Question 35

What does a tall, spikey S wave indicate?

Answer 35

Right ventricular enlargement

Question 36

What diseases increase vagal tone and may lead to sinus arrhythmias?

Answer 36

Respiratory disease
Intra-cranial disease
Intra-ocular pressure
Pleural disease 
Thoracic masses 
Abdominal disease

Question 37

What affects the MEA?

Answer 37

Bundle branch blocks

Ventricular enlargement

Question 38

How can you tell the location of a bundle branch block? And how can you tell the location of the origin of VPC?

Answer 38

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

Question 39

How can you tell the origin of a supra ventricular premature complex from the presence / absence of p waves?

Answer 39

P wave associated - sinus

P waves of different morphology - atrial eg: fibrillation line

Question 40

What is the normal MEA for a dog?

Answer 40

40-100 degrees

Question 41

What is the normal MEA for a cat?

Answer 41

0-160 degrees