Oral vs Intravenous Diltiazem for Rapid Atrial Fibrillation/Flutter Trial

Atrial fibrillation (AF), a supraventricular tachyarrhythmia, is the primary diagnosis for over 467,000 hospitalizations each year. Historically, there have been two approaches to managing AF in the emergency department (ED): rate control and rhythm control.

The AFFIRM trial compared rate and rhythm control in 4,060 patients. It found no difference in mortality with the rate control approach and less hospitalizations. As a result, both rhythm and rate control are options in stable patients with an AF duration of < 48 hours. After 48 hours, rate control is preferred because of the increased risk of ischemic stroke. The subsequent RACE II trial, established that lenient heart rate control (HR <110 beats/min) was as effective as strict control (HR <80 beats/min) in preventing cardiovascular events and required less outpatient visits to achieve the goal HR. As a result of both the AFFIRM and RACE II trials, a rate control approach with a goal HR of <80-110 beats/min is the management plan for a majority of patients who present to the ED in AF. According to the American Heart Association 2014 guidelines, the initial acute, emergent management of atrial fibrillation and flutter (AFF) are similar and there are a number of medications used for rate control including beta blockers and non-dihydropyridine calcium channel blockers.

Diltiazem, a non-dihydropyridine calcium channel blocker, is often the medication of choice in the management of AFF due to its ability to be given as an intravenous (IV) push, continuous infusion, and oral (PO) immediate release or extended release tablet. In the ED, a loading dose of IV diltiazem 0.25 mg/kg is usually administered to obtain a heart rate of < 110 beats/min or a decrease of at least 20% in the ventricular rate. If this does not work then a second bolus of 0.35mg/kg is administered. Once rate control of <110 beats/min or a 20% decrease in ventricular rate is obtained physicians typically chose between oral immediate release diltiazem tablet or IV continuous infusion diltiazem to maintain heart rate control. Both options allow for dose changes in the short term. The oral immediate release diltiazem tablet has a fast onset of action of 30-60 minutes and is dosed every 6 hours. Intravenous continuous infusion diltiazem has a variable onset of action with a titration frequency of every 15-30 minutes. The use of oral diltiazem allows for possible placement on a monitored general floor bed, whereas an intravenous drip requires placement to step down or intensive level of care. This impacts bed status and length of stay in the emergency department. Both oral and intravenous diltiazem are used clinically; however, no prospective studies exist comparing the two strategies. Retrospective data suggests that both forms are equal in their ability to control heart rate.