Anti-arrhythmics (details)

Question 1

Which ion channels are involved in each stage of the cardiac action potential?

Answer 1

phase 0: sodium
phase 1: potassium
phase 2 and 3: potassium and calcium

Question 2

What are the MOAs of amiodarone?

Answer 2

Blockade of
1) Potassium channels (main effect)
2) Sodium channels
3) Adrenergic receptor
4) Calcium channels

amiodarone has NO EFFECT on phase 0!

Question 3

What is the effect of the different classes of anti-arrythmics on the cardiac action potential?

Answer 3

1A: slow phase 0 depolarisation
1B: shortens phase 3 repolarisation and action potential duration (APD)
1C: slows phase 0 depolarisation
2: suppresses phase 4 depolarisation
3: prolongs phase 3 repolarisation
4: prolongs APD

Question 4

What is the effect of the anti-arrythmics on the effective refractory period (ERP)?

Answer 4

1A: increase
1B: unchanged
1C: unchanged
2: unchanged
3: increase
4: increase

Question 5

What are the clinical uses of class 1C anti-arrythmics?

Answer 5

Refractory ventricular tachycardias that tend to progress to vfib

Question 6

What are the clinical uses of class 2 anti-arrythmics?

Answer 6

1) Tachycardia caused by sympathetic activation
2) Atrial fibrillation
3) AV nodal reentrant tachycardia
4) Reduces sudden arrhythmic death post-MI

Question 7

Discuss the PK properties of amiodarone

Answer 7

• undergoes hepatic metabolism
• hepatic metabolite is still bioactive
• effects are still maintained after discontinuation for a few months

Question 8

What are the clinical uses of amiodarone?

Answer 8

1) Maintain normal sinus rhythm in patients with afib
2) Prevention of reentrant ventricular tachycardia

Question 9

What are the adverse effects of amiodarone?

Answer 9

Symptomatic bradycardia and heart block

Question 10

What are the clinical uses of verapamil?

Answer 10

1) Supraventricular tachycardia
2) Hypertension
3) Angina

Question 11

What are the adverse effects of verapamil?

Answer 11

Hypotension

Question 12

What is the contraindication of verapamil?

Answer 12

Patients with pre-existing depressed cardiac function

Question 13

What is the MOA of adenosine?

Answer 13

1) Suppression of AV nodal conduction and increases AV nodal refractory period
2) Stimulates cardiac potassium channels
3) Inhibits calcium current

Question 14

What are the adverse effects of adenosine?

Answer 14

1) Flushing
2) Shortness of breath or chest burning
3) Induction of AV block or afib
4) Headache
5) Hypotension

Question 15

What is the clinical use of adenosine?

Answer 15

Treatment of supraventricular tachycardia in emergency situations