ECGs

Question 1

identify this ECG

Answer 1

Sinus arrhythmia

Question 2

Identify this ECG

Answer 2

1st degree heart block

Question 3

Identify this ECG

Answer 3

type 2 heart block, mobitz type 1

Question 4

Identify this ECG

Answer 4

type2 heart block, mobitz type 2

Question 5

Identify this ECG

Answer 5

3rd degree heart block

Question 6

Identify this ECG

Answer 6

Atrial fibrillation

Question 7

Identify this ECG

Answer 7

hyperkalaemia

Question 8

Identify this ECG

Answer 8

sick sinus syndrome

Question 9

Identify this ECG

Answer 9

sinus bradycardia

Question 10

Identify this ECG

Answer 10

Sinus tachycardia

Question 11

Identify this ECG

Answer 11

supraventricular premature beats

Question 12

Identify this ECG

Answer 12

supraventricular tachycardia

Question 13

Identify this ECG

Answer 13

ventricular premature contractions

Question 14

Identify this ECG

Answer 14

ventricular tachycardia

Question 15

Identify this ECG

Answer 15

wandering pacemaker

Question 16

Name non pathological arrhythmias

(2)

Answer 16

sinus arrhythmia

wandering pacemaker

Question 17

Name the pathological bradyarrhythmias

8

Answer 17

type 1 heart block

type 2 heart block mobitz type 1

type 2 heart block mobitz type 2

type 3 heart block

sinus bradycardia

hyperkalaemia

hypokalaemia

sick sinus syndrome

Question 18

Name the pathological tachyarrhyhmias

7

Answer 18

ventricular fibrillation

ventricular tachycardia

supraventricular tachycardia

atrial fibrillation

supraventricular premature beats

ventricular premature contractions

sinus tachycradia

Question 19

Describe wandering pacemaker

Answer 19

Heart rate low to mid normal

Associated with sinus arrthymia

Variable amplitude or morphology of P wave

Change in P waves gradually shifts from normal to abnormal

non pathological

Question 20

List differentials for sinus bradycardia

Answer 20

• Increased parasympathetic tone-
• respiratory disease
• gastric irritation
• increased CSF pressure
• Hypothyroidism
• Hypothermia
• Hyperkalaemia
• Hypoglycaemia
• Drug therapy

Question 21

Describe type 1 heart block

Answer 21

Prolonged PR interval

P for every QRS

Due to prolonged conduction across the
AV node

Associated with increased parasympathetic
tone

May be due to drugs - digoxin, calcium
channel blocker, procainamide, beta-
blocker

PR interval can increase with age

May be completely normal for that
dog

Often there are no haemodynamic
abnormalities

No treatment is required

Question 22

Describe type 2 heart block, mobitz type 1

Answer 22

P wave not followed by QRS

PR interval gradually prolongs until
blocked

QRS appears normal

The PR interval immediately preceding
the blocked beat is longer than the PR
interval immediately following the
blocked beat

Due to prolonged conduction across the AV
node

Associated with increased parasympathetic
tone

May be a normal variant

Can be induced by digoxin

Infrequently requires treatment

Question 23

Describe type 2 heart block, mobitz type 2

Answer 23

P wave not followed by QRS

Often has wide QRS complexes

PR is of constant duration

May have multiple P waves not
followed by QRS e.g. 2:1, 3:1 etc

Caused by failure of impulse to
propagate through the Bundle of His or
bundle branches

Associated with organic disease of the
Bundle of His e.g. ischaemia, scarring,
infection, necrosis, granuloma or
tumour

Usually not responsive to atropine or
glycopyrrolate

Can cause reduced cardiac output if
ventricular response rate low

May require treatment if there are clinical
signs

Potential pacemaker candidate

Question 24

Describe type 3 heart block

Answer 24

Atrial rate and rhythm that occurs
independently of a much slower
ventricular rate and rhythm

The ventricular rhythm is an escape from
latent, subsidiary pacemaker foci

QRS may look normal or may be
abnormal depending on the origin of the
impulse

Due to the same aetiologies as for Mobitz
type II block

Can be a consequence of Lyme disease

Cause signs of low output

No response to atropine

May be associated with hypothyroidism

Indication for a pacemaker

Question 25

List differentials for hyperkalaemia

Answer 25

Potassium abnormalities are relatively common metabolic causes of cardiac arrhythmias- * Addisons disease * Urinary tract obstruction * Oliguric/anuric renal failure * Acidosis * DKA

Question 26

Discuss hyperkalaemia and treatment

Answer 26

Decreased amplitude of P wave progressing to atrial standstill Prolonged QRS/bizarre QRS Increased QT duration Tall spiked T waves Decreased R wave amplitude Fluid therapy using NaCl 0.9% Ca gluconate 0.5mg/kg iv slow Glucose + insulin or just glucose NaHCO3 1-2 mEq/kg iv slow Steroid supplementation for Addison’s disease

Question 27

Discuss sick sinus syndrome including treatment

Answer 27

Group of disorders involving the SA node, AV node, Bundle of His and bundle branches Usually involves periods of sinus tachycardia and supraventricular tachycardia interspersed with bradycardia and sinus arrest May have ischaemia or fibrosis of the SA node and conduction system Miniature Schnauzers are over- represented Usually idiopathic Can cause syncopal episodes Atropine is usually not effective Pacemaker implantation is usually the treatment of choice for symptomatic patients

Question 28

List differentials for sinus tachycardia

Answer 28

Sinus rhythm with increased ventricular rate can be due to- pain fever anaemia excitement decreased cardiac output hyperthyroidism

Question 29

Discuss supraventricular tachycardia including potential treatments

Answer 29

May be atrial or junctional in origin •Causes are the same for both types –enlarged atria –ischaemic foci in the atria –drugs therapy especially digoxin or anaesthetics Several isolated beats are of no significance Multiple beats may cause a reduction in cardiac output If the animal is symptomatic then treatment usually comprises digoxin, a calcium channel blocker or a beta- blocker

Question 30

Discuss supraventricular tachycardia

Answer 30

Same aetiologies and therefore treatment as for APCs/supraventricular premature beats Can be paroxysmal and precipitate syncope and collapse Can lead to heart failure through elevation in heart rate

Question 31

Discuss atrial fibrillation

Answer 31

Rapid and irregular rhythm •No visible P waves •Baseline variation - fibrillatory potentials •QRS looks normal in appearance Although the heart rate is usually rapid it may be slower in a giant breed, if there is AV nodal disease also or if drug therapy is being used •Usually secondary to AV insufficiency, cardiomyopathy or congenital heart disease when the atria are stretched Convert the rhythm? –Use quinidine •Slow the rhythm –digoxin –beta-blockers –calcium channel blockers

Question 32

Discuss ventricular premature contractions including treatment

Answer 32

Premature beats QRS is usually wide and bizarre If more than one ectopic focus is present then there will be more than one morphological appearance Ventricular premature contractions - treatment -Lignocaine 2-4mg/kg iv slowly or CRI -Oral ‘lignocaine’, mexilitine 2-5mg/kg BID-TID -Procainamide 6-8mg/kg iv over 5 minutes -Quinidine -Sotalol May not be required if haemodynamically stable when to treat- Greater than 20/minute •Presence of doublets or triplets of abnormal complexes •Multiformed complexes •R on T phenomenon

Question 33

List differential diagnoses for ventricular premature contractions

Answer 33

Associated with ventricular hypertrophy •Associated with myocardial hypoxia •Induced by acidosis •Induced by drugs e.g. digoxin, barbiturates and anti-arrhythmics •May predispose to ventricular tachycardia

Question 34

Identify this ECG

Answer 34

ventricular fibrillation