• No statistical difference in any of the components of the composite outcome of adverse events except for worsening congestive heart failure (CHF) symptoms (33 percent versus 15 percent, P=0.019).
• Worsening CHF was driven by increased oxygen requirement within four hours

Table: secondary outcomes 

EBM Commentary:

1. Non-Randomized Study – This was an observational study which means that unmeasured confounders could have introduced bias into the results.

1. Unbalanced Groups – Patients who received diltiazem were younger with higher baseline blood pressures (BP), so they may have been less likely to become hypotensive, which was defined primarily as systolic BP <90 mmHg, rather than a measured drop in BP.
2. Small Sample Size – This was a single-center study with a small sample size (n=125). The absolute difference between the two drugs was fairly large (11 percent) but it was not statistically significant. It’s possible that a larger sample size would have reported a statistically significant difference. However, the observational nature of the study would still only provide evidence of a correlation, not causation.
3. Observer-Expectancy Effect – The discussion section of the article mentions guidelines recommending against the use of diltiazem in patients with AF and RVR with HFrEF as it may worsen HF, despite minimal confirmatory evidence. Outcomes measured by increased oxygen requirement and inotrope administration can be subjective, and it is possible a greater number of patients in this cohort received interventions based on provider expectations.
4. Lack of Comparator Group – It would have been interesting to compare these results to patients with AF and RVR without heart failure and see if the adverse effects were different between the two treatment groups.

SGEM Bottom Line: We still do not have high-quality evidence to suggest a difference in total adverse outcomes for patients presenting to the ED in AF with RVR and found to have HFrEF treated with IV diltiazem versus IV metoprolol.

Case Resolution: Patient is given metoprolol 5mg IV and her heart rate drops to less than 100 bpm. She is admitted to the hospital under cardiology for further workup and management.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

Thank you to Dr. Timlin Glaser and Dr. Matt Murphy, who are currently residents in emergency medicine at Lehigh Valley Health Network, for their help with this review.

References

1. January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the Heart Rhythm Society. Circulation. 2014;130(23), 2071-2104.
2. Hasbrouck M, Nguyen TT. Am J Emerg Med.2022;58:39-42. doi: 10.1016/j.ajem.2022.03.058.