Diltiazem or metoprolol?

by Bob Stuntz

I remember this coming up frequently during my residency, and the answer widely varied based on which attending I was working with.  It came up the other day as well during a shift.  

One of the questions I get asked frequently is if you should avoid diltiazem if a patient is on beta blockers at home, and vice versa.  From what I have seen, there is no evidence to support this case.  Obviously, these are both AV nodal blocking agents, and the concern would be for complete AV nodal blockade.  However, if they come in in rapid ventricular response, clearly their metoprolol is not cutting it.  So I have not found any evidence that you have to match the IV med to their home meds.  Use what you are comfortable with.  

So if that doesn’t have any impact on your choice, is one better than the other at rate control?  An article in the Emergency Medicine Journal in 2005 showed that both were safe and effective at rate control for rapid a fib.  Diltiazem, however, did achieve rate control faster, and had a higher percentage decrease in ventricular rate (1).  From my standpoint, diltiazem has the advantage here, although you can make the argument that the diltiazem had about a 20 minute advantage, which is of questionable clinical significance.

There are two specific cases where I would say beta blockade has the definite leg up, and this is patients in whom acute coronary syndrome is suspected, or in the treatment of a fib related to thyrotoxicosis.  For thyrotoxic patients, consider an esmolol drip.   Stay AWAY from beta blockers in your COPD patients as it can cause bronchospasm.  

This does not really scratch the surface for a fib, as there is still the topic of cardioversion, instability, digoxin’s role, and the topic of who to anti coagulate.  More to come in future posts and a planned a fib podcast.  

1.  Comparison of the effectiveness of intravenous diltiazem and metoprolol in the management of rapid ventricular rate in atrial fibrillation.  Demircan C, et al.  Emerg Med J 2005; 22: 411-414.  

2. Acute Management of Atrial fibrillation.  Khoo CW, Lip GYH.  Chest 2009; 135(3): 849-859.