Important dysrrhythmias in horses

Question 1

1st degree AV block

Answer 1

Lengthening of the PR interval

Question 2

2nd degree AV block

Answer 2

Normal physiological response to higyh blood pressure

Can be abloished by various stresses

Can be difficult to tell between atrial fibrillation

Question 3

3rd degree AV block

Answer 3

Always pathological

Complete dissociation of the atria and ventricles

Question 4

Atrial fibrillation

Answer 4

Most common pathological dysrhythmia in horses

Can be an important cause of poor performance

Question 5

ECG of atrial fibrillation

Answer 5

Abscence of p waves

Normal QRS-t complexes - occuring irregularly

Question 6

Types of atrial fibrillation

Answer 6

Paroxysmal atrial fibrillation

Lone atrial fibrillation

Secondary atrial fibrillation

Question 7

Paroxysmal atrial fibrillation

Answer 7

Peak fitness, peak exercise

Sudden loss of performance or collapse

Extreme tachydysrhythmia (>220bpm)

Gastrointestinal disease (eg colic)

Question 8

Lone atrial fibrillation

Answer 8

‘No’ underlying myocardial or endocardial disease

Question 9

Secondary atrial fibrillation

Answer 9

Cardiac (atrial) enlargement

Question 10

Diagnosis of atrial fibrillation

Answer 10

Auscultation
○ Irregularly irregular rhythm
○ Rate normal/bradydysrhythmia
○ No 4th heart sound
○ Loud 3rd heart sound
○ Varying intensity

• Resting ECG
  ○ Base-Apex lead
  ○ Alivecor

Question 11

Treatment of atrial fibrillation

Answer 11

Quinidine

Alternative treatments:
- amiodarone (expensive)
- Flecainide

Transvenous cardioversion

Question 12

Quinidine for atrial fibrillation

Answer 12

Prognosis 80% if treated within 3mo of onset and no underlying disease

Side effects: diarrhoea and colic, significant cardiac side effects

Given by stomach tube as very irritant

Quinidine sulphate

Question 13

Transvenous cardioversion for atrial fibrillation

Answer 13

For animals with AF for >3mo, significant cardiac disease, ventricular techycardia

Good success rates

Drug co-therapy (quinidine gluconate, solatol, amiodarone, magnesium sulfate)

Question 14

Management after AF treatment

Answer 14

Rest – especially after TVEC
○ Controversial in Quinidine treated - only rest for a week
○ Myocardial healing

Holter ECG – frequency of APCs
○ In humans APCs are not correlated with ERAF

Steroids
○ No proven effectiveness

Question 15

Auscultation of atrial fibrillation

Answer 15

Irregular (irregular) rhythm

Rate normal / brady dysrhythmia

No 4th heart sound

Varying intensity

Question 16

Jugular pulses in atrial fibrillation

Answer 16

Often obvious

Varying heights

Biphasic

Question 17

Auscultation of second degree AVB

Answer 17

Irregular (regular) rhythm

Bradydysrhythmia

S4 maybe audible

Intensity similar

Question 18

Jugular pulses in 2nd degree AVB

Answer 18

Triphasic

Question 19

Signs that make you suspicious of ventricular tachycardia

Answer 19

Poor performance and lethargy

Resp infection on yard recently