Cardio: Class IV Antiarrhythmics

Question 1

What is the basic function of class IV antiarrhythmics?

Answer 1

They, like the class II drugs, slow heart rate. Class IV drugs do so by blocking nodal calcium channels.

Question 2

What type of calcium channels do the class IV drugs block?

Answer 2

L-type, also called non-dihydropyridine (think of the L-shaped handle of the Non-Dairy soft-serve dispenser)

Question 3

What are the classic class IV drugs?

Answer 3

Verapamil (Very Vanilla ice cream)Diltiazem (Delicious Dark chocolate)

Question 4

What do calcium-channel blockers do to the cardiac action potential?

Answer 4

It slows the phase 0 upslope, thereby decreasing sinus activity, prolonging conduction velocity, and lengthening refractory period –all nodal effects.

Question 5

True or false: class IV drugs can cause increased QT interval.

Answer 5

False. They cause increased PR interval, because they slow conduction between the atria and ventricles.

Question 6

Which part of the heart can class IV drugs treat?

Answer 6

The atria (think of the broken bottom half of the heart sign), because class IV drugs block nodal rhythms

Question 7

What kind of arrhythmias can class IV drugs treat?

Answer 7

Atrial fibrillation and atrial flutter (think of the TV with static in the shop) because they prolong conduction time and can prevent the atria from inducing ventricular tachycardias