Beta blocker vs Calcium channel blocker for AF

[zzyzx]

I understand how calcium-channel blockers work in AF with RVR. They slow down impulses going through the AV node, thus lowering the ventricular rate.

However, I don't totally understand how beta blockers work in slowing down AF with RVR. I always thought that beta blockers only have effects on slowing down the rate of the SA node and the contractility of the heart. But do they also have an effect on the AV node?

[PaSSiNGaS, MSN]

Beta blockers are class II antiarrhythmics. They block automaticity and slow AV node conduction.

[twozer0, NP]

imagine that your beta receptors have a constant amount of epinephrine surrounding them. If the constant amount leads to AF with RVR than reducing the amount of receptor binding to the beta receptor will cause a slow in impulse (a decrease from the current impulse standard). Less epi to bind to beta receptors = less impulse, which is why you see a slowing of the heart rate (and other beta functions if not giving a cardioselective blocker).

CCB's block the calcium channel required for muscle contractility. In the end you get the same results but through a different pathway. The gold standard is CCB's but if they fail beta blockers are the next best choice.

[zzyzx]

I know that beta blockers work through a similar pathway, blocking calcium influx/exit. I guess what I'm not understanding is which has a better effect on the AV node and why. It seems that CCB are better at block/slowing the AV node, which is why they are more effective for slowing conduction in AF with RVR.

[twozer0, NP]

I know that beta blockers work through a similar pathway, blocking calcium influx/exit. I guess what I'm not understanding is which has a better effect on the AV node and why. It seems that CCB are better at block/slowing the AV node, which is why they are more effective for slowing conduction in AF with RVR.

I think you have it backwards. Beta Blockers do not block calcium, they block the binding of epi and norepi to beta receptors. You really need not concern yourself with the node. When giving this type of medication we are dealing with process that preceeds the electrical conduction and hence the nodes.