Week 5 - Cardiovascular Antidysrhythmics

Question 1

What are the classes of antidysrhythmic drugs and the type of drug?

Answer 1

Class I - Na channel blocker
Class II - Beta blocker
Class III - K channel blocker
Class IV - Ca channel blocker

Question 2

What are the actions of Class I drugs and an example?

Answer 2

Quinidine

• reduce depolarisation
• inhibit contraction

Question 3

What are the actions of Class II drugs and an example?

Answer 3

Propranolol

• inhibit sympathetic activity
• -via B1-receptors, SA and AV nodes

Question 4

What are the actions of Class III drugs and an example?

Answer 4

Amiodarone, sotalol

• prolong action potential
• increase refractory period
• block re-entrant tachycardias

Question 5

What are the actions of Class IV drugs and an example?

Answer 5

Verapamil

• reduce after-depolarisations
• suppress ectopic beats
• slow conduction in SA and AV nodes

Question 6

What are the actions of Class Ib drugs and an example?

Answer 6

Lidocaine

• shorten refractory period
• decrease duration of the action potential

Question 7

What are the actions of Class Ic drugs and an example?

Answer 7

Flecainide

-inhibit conduction through the His-Purkinje system

Question 8

What are the actions of Class Ia drugs and an example?

Answer 8

Disopyramide

-prolongs repolarisation

Question 9

Describe the events of the cardiac cycle

Answer 9

• Na influx causes depolarization for contraction to occur
• K outflow starts initial repolarization
• K slowed slow inflow of Ca
• Ca inflow stops
• K outflow accelerates for complete repolarisation

Question 10

How are drugs used to treat cardiac dysrhythmias?

Answer 10

•Antidysrhythmic drugs block Na channels
o Inhibiting contraction by reducing depolarisation
•Prolong the action potential by delaying outflow of K
•Slow the action potential by blocking Ca influx
o Reducing after-depolarisation