Intravenous Continuous Infusion vs. Oral Immediate-release Diltiazem for Acute Heart Rate Control

INTRODUCTION: Atrial fibrillation (AF) is a common diagnosis of patients presenting to the emergency department (ED). Intravenous (IV) diltiazem bolus is often the initial drug of choice for acute management of AF with rapid ventricular response (RVR). The route of diltiazem after the initial IV loading dose may influence the disposition of the patient from the ED. However, no studies exist comparing oral (PO) immediate release and IV continuous infusion diltiazem in the emergency setting. The objective of this study was to compare the incidence of treatment failure, defined as a heart rate (HR) of >110 beats/min at four hours or conversion to another agent, between PO immediate release and IV continuous infusion diltiazem after an initial IV diltiazem loading dose in patients in AF with RVR. METHODS: This was a single-center, observational, retrospective study conducted at a tertiary academic medical center. The study population included patients ≥18 years old who presented to the ED in AF with a HR > 110 beats/min and received an initial IV diltiazem loading dose. We used multivariate logistic regression to assess the association between routes of administration and treatment failure. RESULTS: A total of 111 patients were included in this study. Twenty-seven percent (11/41) of the patients in the PO immediate-release group had treatment failure compared to 46% (32/70) in the IV continuous-infusion group. The unadjusted odds ratio (OR) of treatment failure with PO was less than IV at 0.4 (95% confidence interval [CI] [0.18, 0.99], p = 0.046). When we performed a multivariate analysis adjusted for race and initial HR, PO was still less likely to be associated with treatment failure than IV with an OR of 0.4 (95% CI [0.15, 0.94], p = 0.041). The median dose of PO diltiazem and IV continuous infusion diltiazem at four hours was 30 mg and 10 mg/h, respectively. CONCLUSION: After a loading dose of IV diltiazem, PO immediate-release diltiazem was associated with a lower rate of treatment failure at four hours than IV continuous infusion in patients with AF with RVR.