5.1.4 Class V Anti-arrhythmics

Question 1

How is adenosine administered?

Answer 1

Rapid IV bolus

Very short half-life

Question 2

What is the mechanism of adenosine?

Answer 2

Binds to A1 receptors and blocks adenylyl cyclase

Reduces cAMP

Activates K+ currents in AVN and SAN

Hyperpolarisation, decreased HR

Leads to decreased Ca2+ currents, increased refractory period in AVN

Question 3

What is the use of adenosine?

Answer 3

Slows AV conduction

Question 4

When is adenosine used?

Answer 4

Convert re-entrant supraventricular arrhythmias

Diagnosis of coronary artery disease

Question 5

How is ivabradine given?

Answer 5

Oral

Question 6

What is the mechanism of ivabradine?

Answer 6

Blocks If ion current, highly expressed in the SAN

Question 7

What are the cardiac effects of ivabradine?

Answer 7

Slows the sinus node but does not affect blood pressure

Question 8

What are the side effects of ivabradine?

Answer 8

Flashing lights
Teratogenicity not known- avoid in pregnancy

Question 9

When is ivabradine used?

Answer 9

Reduce inappropriate sinus tachycardia

Reduce heart rate in heart failure and angina

As there is no BP drop, very useful in postural orthostatic tachycardia syndrome

Question 10

What is digoxin?

Answer 10

Cardiac glycoside

Question 11

What is the mechanism of digoxin?

Answer 11

Enhances vagal activity - Increases K+ currents, decreases Ca2+ currents, increases refractory period

Slows AV conduction and slows HR

Question 12

When is digoxin used?

Answer 12

Treatment to reduce ventricular rates in AF and flutter

Question 13

What is atropine?

Answer 13

Selective muscarinic antagonist

Question 14

What are the cardiac effects of atropine?

Answer 14

Blocks vagal activity to speed AV conduction

Increases HR

Question 15

When is atropine used?

Answer 15

Treatment of vagal bradycardia

Question 16

Label the image

Answer 16

Amiodarone most efficacious

Question 17

Label the image

Answer 17

Amiodarone least safe