Class 2 (Anti-Arrythmics)

Question 1

What are class 2 anti-arrythmics? Where do they work?

Answer 1

They are Beta blockers, and they work on the SA and AV node (pacemakers) not on the myocytes. (Decreases the speed of SA and AV nodes by increasing parasympathetic activity).

Question 2

Regarding the AP graph (of the nodal cells) what would the beta blockers do?

Answer 2

The Pacemaker current (phase 4) will have a smaller slope, meaning that it will induce bradycardia by prolonging the time it requires for the heart to reach threshold after repolarization.

Question 3

What are the drugs of Beta blockers and their selectivity?

Answer 3

Proponol is non selective, Acebutolol is ß1 selective, and esmolol (which is IV only).

Question 4

Where are ß blockers primarily used?

Answer 4

Post MI Px is the primary use, and for Supraventricular Tachycardias (SVT’s) to protect against progression to ventricular arrythmias.

Question 5

What drug would you consider using during an acute SVT?

Answer 5

Esmolol.

Question 6

Why would you use ß blockers for post MI?

Answer 6

Not necessarily for the anti-arrythmic effects, but moreso because of the negative ionotropic effects so that you decrease oxygen demand.