Arrhythmias (Yr4)

Question 1

what is the difference between a ventricular and supraventricular arrhythmia on an ECG?

Answer 1

ventricular - wide bizarre QRS complex
supraventricular - normal ORS complex

Question 2

what are the two categories of tachyarrhythmias?

Answer 2

supraventricular
ventricular

Question 3

what are the features of ventricular tachyarrhythmias on an ECG?

Answer 3

wide bizarre QRS and oppositely directed T wave

Question 4

what are the classes of anti-arrhythmic drugs?

Answer 4

1. sodium channel blockers
2. beta blockers
3. potassium channel blockers
4. calcium channel blockers

Question 5

how do sodium channel blockers work as an anti-arrhythmic drug?

Answer 5

slows conduction by blocking sodium channels, slows phase 0 (cell to cell conduction)

Question 6

what is the site beta blockers act on?

Answer 6

nodal tissue (also ectopic focuses)

Question 7

how do potassium channel blockers work?

Answer 7

delay repolarisation which lengthens the action potential duration

Question 8

what is the site of action of calcium channel blockers?

Answer 8

nodal tissue (SAN and AVN)

Question 9

what are examples of supraventricular tachyarrhythmias?

Answer 9

sinus tachycardia
ectopic focus (atrial or junctional)
re-entry circuit (atrial fibrillation or accessory pathway)

Question 10

what can cause sinus tachycardia?

Answer 10

physiological - pain, stress…

Question 11

how can atrial fibrillation be differentiated from other supraventricular tachycardias?

Answer 11

atrial fibrillation is irregularly irregular (SVTs are regular)

Question 12

what is the emergency treatment options if presented with a dog with a supraventricular tachycardia?

Answer 12

vagal manoeuvre (enhance vagal tone)
esmolol (beta blocker)
diltiazem (oral or IV)

Question 13

what is an accessory pathway?

Answer 13

abnormal connection (not the AV node) between the atria and ventricles allowing conduction between the two

Question 14

what age dogs typically present with accessory pathways?

Answer 14

young (1-2 year old dogs)

Question 15

what pathology is typically associated with atrial fibrillation?

Answer 15

enlarged atria (can have CHF)

Question 16

how can atrial fibrillation be treated?

Answer 16

slow conduction though AVN - digoxin, calcium channel blockers, beta blockers

Question 17

can beta blockers be used in patents with CHF?

Answer 17

no!!

Question 18

what are the effects of digoxin on the heart?

Answer 18

negative chronotrope
positive inotrope (mild)
(it is a vagomimetic)

Question 19

what calcium channel blocker can be used for atrial fibrillation?

Answer 19

diltiazem

Question 20

why may you use digoxin and diltiazem together in cases of atrial fibrillation?

Answer 20

better control of heart rate than just using one

Question 21

what cases should beta blockers not be used for?

Answer 21

anything that has uncontrolled CHF

Question 22

when should ventricular tachycardia be treated?

Answer 22

assess the patient… if the HR is haemodynamically significant

Question 23

what catastrophic event can ventricular tachycardia lead to?

Answer 23

ventricular fibrillation

Question 24

what are some underlying causes of ventricular ectopics?

Answer 24

underlying cardiac disease (CHF, cardiomyopathies)
catecholamines (stress, pain…)
acidosis
hypokalaemia
thoracic trauma
drugs

Question 25

when should you treat ventricular ectopics?

Answer 25

if haemodynamically significant
if very fast
if multifocal