Written by Clay Smith
There was no difference in rate control (<110 beats per minute at 2 hours) for patients with atrial fibrillation with rapid ventricular response between IV diltiazem or metoprolol.
Why does this matter?
Yesterday, we learned there was little difference in the two drugs in a small retrospective study. The AHA doesn’t recommend one agent over another for atrial fibrillation with rapid ventricular response (a-fib, RVR). Pharmacokinetically, diltiazem may work faster and have a shorter duration of action than metoprolol. So, which agent should you choose? What does this larger cohort show?
Race for rate control
This was a single center retrospective study of patients with a-fib with RVR, comparing 166 who received metoprolol and 183 who received diltiazem. For rate control 2 hours after the last bolus, there was no statistical difference: 45.8% metoprolol vs 42.6% diltiazem, p = 0.590. There was a statistically but not clinically meaningful reduction in heart rate at 30 minutes, by 6 beats per minute, favoring diltiazem. Bradycardic events were statistically the same. The rate of diastolic hypotension <60 was higher in the diltiazem cohort, but systolic hypotension was statistically the same. In short, this is low quality evidence that these agents are almost the same for rate control in patients with a-fib with RVR. In my practice, if a patient is already taking a beta-blocker chronically, I will not add on an IV non-dihydropyridine calcium channel blocker (CCB) and vice versa. Why not mix beta-blockers and CCBs? Anecdotally, I have seen profound bradycardia in such cases if patients happen to spontaneously convert to normal sinus rhythm. Take this advice for what it’s worth, which is probably not much.
Evaluation of metoprolol versus diltiazem for rate control of atrial fibrillation in the emergency department. Am J Emerg Med. 2020 Nov 22;S0735-6757(20)31063-9. doi: 10.1016/j.ajem.2020.11.039. Online ahead of print.