Anti-arrhythmic drugs

Question 1

Class Ia anti-arrhythmics

Answer 1

Disopyramide, quinidine

Voltage-sensitive sodium channel blockade

Prolong QT interval, increase QRS duration.

Indication - Ventricular and supraventricular arrhythmias

Adverse effects - oedema

Question 2

Class Ib anti-arrhythmics

Answer 2

Lidocaine

Voltage-sensitive sodium channel blockade

Prolong QT interval, increase QRS duration.

Indication - CPR (used IV) and paroxysmal atrial fibrillation

Adverse effects - oedema

Question 3

Class Ic anti-arrhythmics

Answer 3

Flecainide, propafenone

Voltage-sensitive sodium channel blockade

Prolong QT interval, increase QRS duration.

Indication - Ventricular ectopic beats “pill in pocket”

Adverse effects - oedema

Question 4

Class II anti-arrhythmics

Answer 4

Beta-blockers

Atenolol, bisoprolol, metoprolol

Beta-adrenergic receptor blockade - reduction in adrenergic effects on rate and inotropy

Indication - Prophylaxis of paroxysmal atrial tachycardia or fibrillation

Adverse effects - Hypotension

Question 5

Class III anti-arrhythmics

Answer 5

Potassium channel blockers

Amiodarone, dronedarone, sotalol (sotalol also has some beta blocker activity)

Potassium channel blockade, also evidence of beta blocker and calcium channel blocker properties - prolong QT interval

Indication - Supraventricular, nodal and ventricular tachyarrhythmias, atrial fibrillation (CPR - used IV)

Adverse effects - Nausea, vomiting

Question 6

Class IV

Answer 6

Calcium channel blockers (phenylalkylamine and benzodiazepine subclasses)

Verapamil, diltiazem (for arrhythmia)

Cardiac calcium channel blockade - reduction of action potential and cardiac output

Indication - Supraventricular tachycardia (especially paroxysmal SVT)

Adverse effects:
Hypotension (verapamil)
Constipation (diltiazem)

Question 7

Cardiac glycosides

Answer 7

Digoxin

Reduces conductivity of AV node

Indication - arrhythmias - AF, congestive heart failure

Adverse effects - fatigue, nausea

Question 8

Adenosine

Answer 8

Activates adenosine receptors - causes hyperpolarisation. Slows conduction through AV node

Indications - supraventricular tachycardia

Adverse effects - nausea

Contraindicated in obstructive airway disease

Question 9

Antimuscarinic

Answer 9

Atropine

Blockade of vagal muscarinic acetylcholine receptors

Indications - emergency bradycardia

Adverse effects - urinary retention

Question 10

Magnesium

Answer 10

Magnesium sulfate (IV)

MoA unclear - possible alteration of Na+, K+ and Ca2+ ion balance via ion channels and transporters

Indications - Emergency arrhythmia (also used IV for emergency asthma)

Adverse effects - electrolyte irregularities