(Last Updated On: December 4, 2018)

We continue the series with Knowledge Bomb #21. The purpose and motivation for this series is outlined in the first entry and extensively in an ALiEM IDEA series blog entry.

Background

Atrial fibrillation (afib) with rapid ventricular rate (RVR) can lead to adverse effects on cardiovascular hemodynamics. Sustained elevated rates of disorganized atrial electrical activity leads to the absence of the “atrial kick” and decreases diastolic filling time. Over time, these effects can lead to cardiomyopathy. The question arises in how to best manage it.

The AFFIRM trial¹ (2002) is well known for investigating rate vs. rhythm management in afib patients. The conclusion was no difference in mortality; however, there were fewer hospitalizations with rate control than with rhythm control. Afterwards, the RACE II trial² (2010) investigated whether lenient or strict rate control can prevent adverse cardiovascular events. The study concluded that, in patients with permanent afib, lenient heart rate control was non-inferior to aggressive control and led to fewer clinic visits for maintenance.

These studies support management of afib in the outpatient setting. What about when a patient presents to the ED with symptomatic afib with RVR? This is a common presenting problem and ED docs typically reach for either a beta-blocker or a calcium channel blocker for stable patients.

One option for rate control is diltiazem, a non-dihydropyridine calcium channel blocker that has been shown to be superior to digoxin, metoprolol, and amiodarone in the management of afib. Diltiazem can be given as a loading dose 0.25mg/kg IV over 2 minutes and followed by a continuous IV infusion that has immediate onset of action and may be titrated every 15-30 minutes. The immediate release oral diltiazem has an onset of action of 30-60 minutes and can be re-dosed every 6 hours. Given the options of continuous IV infusion versus oral option, a patient’s disposition can vary widely to either home, general medical floor, step-down, or the ICU.

Question

After an IV diltiazem infusion load, will IV continuous or oral immediate-release diltiazem be more effective for acute heart rate control?

Article

KN Means, AE Gentry, TT Nguyen. IV Continuous Infusion vs. Oral Immediate-release Diltiazem for Acute Heart Rate Control. (Feb 2018). Western Journal of Emergency Medicine, Vol 19, No. 2 [paper]

Study Design

This was a single-center, observational, retrospective study at a tertiary academic medical center. 111 patients were included with 41 patients in the PO group and 70 patients in the IV group. Inclusion criteria were ≥ 18 years old, heart rate ≥ 110, and received IV diltiazem load. Exclusion criteria were pregnancy, prisoners, or history of cardioversion or antiarrhythmic in prehospital or in the ED. Treatment failure was assessed after 4 hours to allow time for the IV and PO medication to achieve peak levels of effectiveness. Treatment failure was defined as heart rate ≥ 110, a switch from PO to IV infusion, addition of another IV bolus, or a switch to another rate control or antiarrhythmic.

Results

In the PO group, the average initial dose of diltiazem was 30-60mg and the length of stay of patients was a mean of 4.7 days and median 3 days. Treatment failure was 27% with an adjusted odds ratio 0.4 (95 CI [0.15, 0.94], p = 0.041). In the IV continuous infusion group, median dose was 10mg/hr (with a range of 2.5-20mg/hr) and the length of stay was a mean of 9 days and median 5 days. Treatment failure was 46%. No patients required vasopressors or had diltiazem discontinued due hypotension.

Bomb!

PO immediate release diltiazem is associated with less treatment failure at 4 hours, higher odds to be admitted to the general medical floor and a shorter length of stay (by 2 days) than IV continuous diltiazem infusion.

Discussion

The results of the study show that oral immediate release diltiazem is non-inferior to intravenous continuous infusion in heart rate control in patients with afib with RVR. The results show that heart rate can be effectively controlled with oral medication and lead to more general floor admissions and decreased length of hospital stay. In a time when there are intravenous drug shortages and hospital overcrowding, the ability to effectively manage patients with de-escalated care is significant for the utilization of resources and for the patient. Moreover, oral medications free up nursing and ancillary staff workload by reducing the frequency of administering or titrating medications. Also, the extra days of hospitalization in the IV group were likely related to additional monitoring time as patients were transitioned from IV to oral medications.

However, there are limitations with this retrospective study. There is a small sample size, low power, and incomplete documentation of severity of symptoms. Also, the initial heart rate of the IV group was significantly higher than the PO group, which may suggest that the patients may have been more critically ill and determined by the provided to need IV management. With the IV group, the average dosage was 10mg/hr (maximum is 15mg/hr) which suggest that some patients may have been sub-optimally dosed.

There are limitations to this study and it would benefit from a larger, multicenter, blinded, randomized control trial. However, the differences in patients’ dispositions (medical floor vs. ICU) are significant enough for me to try oral heart rate management over IV continuous infusion in future patients. If I can spare nursing workload, decrease ICU utilization, and reduce hospital length of stay while still sustaining heart rate control, I believe it will benefit patients and hospital efficiency and workflow.

 

Lily Cheng is an EM/IM resident, class of 2022

 


Citations

¹ Wyse DG, Waldo AL, Dimarco JP, et al. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med. 2002;347(23):1825-33. [paper]

² Van gelder IC, Groenveld HF, Crijns HJ, et al. Lenient versus strict rate control in patients with atrial fibrillation. N Engl J Med. 2010;362(15):1363-73. [paper]


Knowledge Bomb! is presented during Resident Educational Conference and discussed among residents and attendings in the UIC EM program. Adrian Romero, MD and Elspeth Pearce, MD editors.