17) Cardiac Arrhythmias

Question 1

Describe some abnormal impulse generations in the heart:

Answer 1

Delayed or early afterpolarisation

Ectopic focus

Question 2

Describe some abnormal conduction that can occur in the heart:

Answer 2

Conduction block

Re-entry loops

Question 3

What is circus movement (in terms of conduction)?

Answer 3

Part of conduction pathway is blocked so impulse travels in retrograde fashion, re-exciting some cells

Question 4

Describe Wolf-Parkinson-White syndrome:

Answer 4

Accessory pathway between atria and ventricles (bundle of Kent), that doesn’t have rate slowing properties of AVN

Question 5

What are the general actions of arrhythmia drugs on impulse generation and conduction?

Answer 5

Decrease funny current slope in pacemaker cells
Raise threshold to prolong action potential
Decrease conduction velocity
Increase refractory period

Question 6

What are examples of class Ia anti-arrhythmics?

Answer 6

Quinidine and procainamide

Question 7

What is the mechanism of action of class Ia anti-arrhythmics?

Answer 7

Decrease conduction, increase refractory period and increase AP threshold by sodium channel blocking

Question 8

When are class Ia anti-arrhythmics indicated?

Answer 8

Prevent AF

Ventricular arrhythmias

Question 9

What are the side effects of class Ia anti-arrhythmics?

Answer 9

Hypotension 
Proarrthymia
Dizziness
Confusion 
Lupus like syndrome (procainamide)

Question 10

What are examples of class Ib anti-arrhythmics?

Answer 10

Lidocaine, mexiletine

Question 11

What are examples of class Ic anti-arrhythmics?

Answer 11

Flecainide, propafenone

Question 12

What are examples of class II anti-arrhythmics?

Answer 12

Propanolol, metoprolol, bisoprolol, esmolol

Question 13

What are examples of class III anti-arrhythmics?

Answer 13

Amiodarone, sotalol

Question 14

What are examples of class IV anti-arrhythmics?

Answer 14

Verapamil, diltiazem

Question 15

What is the mechanism of action of class Ib anti-arrhythmics?

Answer 15

Sodium channel blockers (fast association) - decrease Na+ conduction in fast beating or ischemic tissue

Question 16

When are class Ib anti-arrhythmics indicated?

Answer 16

Ventricular tachycardia

Question 17

What are the side effects of class Ib anti-arrhythmics?

Answer 17

Dizziness, drowsiness, abdominal upset

Question 18

What is the mechanism of action of class Ic anti-arrhythmics?

Answer 18

Sodium channel blockers (slow association) - decrease sodium entry, increase refractory period

Question 19

When are class Ic anti-arrhythmics indicated?

Answer 19

Supraventricular arrhythmia (fib and flutter)
Premature ventricular contractions
WPW

Question 20

What are the side effects of class Ic anti-arrhythmics?

Answer 20

Pro-arrhythmic
Sudden death in previous MI
CNS and GI effects

Question 21

What is the mechanism of action of class II anti-arrhythmics?

Answer 21

Beta blockers
Decrease conduction through AVN
Decrease depolarisation

Question 22

When are class II anti-arrhythmics indicated?

Answer 22

Tachycardia
Protect ventricles from high atrial rate
Convert re-entrant arrhythmias

Question 23

What are the side effects of class II anti-arrhythmics?

Answer 23

Bronchospasm, hypotension

Question 24

What is the mechanism of action of class III anti-arrhythmics?

Answer 24

Increase refractory period and prolong repolarisation by blocking K+ channels

Question 25

When are class III anti-arrhythmics indicated?

Answer 25

Ventricular tachycardia | WPW

Question 26

What are the side effects of class III anti-arrhythmics?

Answer 26

Amiodarone: pulmonary fibrosis, hepatic injury, thyroid disease, optic neuritis General: pro-arrhythmic, fatigue, insomnia

Question 27

What is the mechanism of action of class IV anti-arrhythmics?

Answer 27

Ca2+ channel blockers - slow conduction through AVN, increase refractory period

Question 28

What are the side effects of class IV anti-arrhythmics?

Answer 28

Hypotension, decreased CO, GI problems

Question 29

When are class IV anti-arrhythmics indicated?

Answer 29

Supraventricular tachycardia, convert re-entry

Question 30

What is the mechanism of action of adenosine?

Answer 30

Activation of K+ channels in AVN and SAN causing hyperpolarisation and decrease HR

Question 31

When is adenosine used?

Answer 31

Convert re-entrant supraventricular arrhythmias

Question 32

What is the mechanism of action of vernakalant?

Answer 32

Blocks atrial specific K+ channels to slow atrial conduction

Question 33

When is vernakalant used?

Answer 33

Convert AF to sinus

Question 34

What is the mechanism of action of ivabradine?

Answer 34

Blocks the funny current in sinus node to slow HR

Question 35

When is ivabradine used?

Answer 35

Sinus tachycardia, angina, heart failure

Question 36

What is the mechanism of action of digoxin? And when is it used?

Answer 36

Decreases conduction at AVN, increases vagal activity | Reduce ventricular rate in AF

Question 37

What is the mechanism of action of atropine? When is it used?

Answer 37

Selective muscarinic antagonist that blocks vagal activity to increase HR in vagal bradycardia

Question 38

What are the principles of AF treatment?

Answer 38

Rate control | Rhythm control