Session 3b: Class V and Other Antiarrhythmics

Question 1

What class of antiarrhythmic is adenosine?

Answer 1

Class V

Adenosine is also known by the brand name Adenocard.

Question 2

What is the mechanism of action for Class V antiarrhythmics like adenosine?

Answer 2

Acts on adenosine receptors, especially in the AV node

This interrupts re-entry rhythms and inhibits calcium currents.

Question 3

What are the primary indications for adenosine?

Answer 3

• Terminating narrow-complex PSVTs
• Pharmacological stress-testing
• Diagnostic testing (e.g. for atrial flutter or wide-complex tachycardia)

Question 4

What is the route of administration for adenosine?

Answer 4

Intravenous

Adenosine has a very short half-life.

Question 5

List some adverse effects of adenosine.

Answer 5

• AV block
• Chest pain
• Nausea
• Proarrhythmic consequences (e.g. degeneration of atrial flutter or PSVT into atrial fibrillation)

Question 6

What are the contraindications for using adenosine?

Answer 6

• Second-degree AV block
• Third-degree AV block
• History of asthma
• Sick sinus syndrome

Question 7

How does dipyridamole interact with adenosine?

Answer 7

It inhibits the breakdown of adenosine.

Question 8

What is the mechanism of action for ivabradine?

Answer 8

Selectively inhibits the funny current (If) in the SA node

This modulates the slow depolarization phase of the action potential.

Question 9

What are the indications for ivabradine?

Answer 9

• Heart failure with reduced EF with persistently elevated heart rate (>70bpm)
• Inappropriate sinus tachycardia

Question 10

What is the typical dose and route for ivabradine?

Answer 10

5-7.5mg BID orally.

Question 11

List some adverse effects of ivabradine.

Answer 11

• Bradycardia
• Increased risk of atrial fibrillation
• Reversible visual scotomata (e.g. seeing flashing lights)

Question 12

What are the contraindications for ivabradine?

Answer 12

• Third-degree AV block
• Severe hypotension
• Resting heart rate <70bpm
• Cardiogenic shock
• Prolonged QT interval
• Acute decompensated heart failure

Question 13

How do Class II and Class IV drugs interact with ivabradine?

Answer 13

They can increase the bradycardia effect of ivabradine.

Question 14

How does adenosine treat PSVT?

Answer 14

Slows conduction through the AV node, interrupting re-entry pathway and restoring normal sinus rhythm.

Question 15

Why should patients with a heart rate below 70bpm avoid ivabradine?

Answer 15

Ivabradine slows depolarization phase 4 of the SA node action potential, resulting in reduced heart rate.