Effect of Early Initiation of Oral Diltiazem Therapy on Time to Effective Heart Rate Control in Patients With Atrial Fibrillation or Atrial Flutter Treated With Intravenous Diltiazem

Early initiation of oral diltiazem during continuous intravenous (IV) diltiazem infusion for treatment of atrial fibrillation or atrial flutter (AF/AFL) with rapid ventricular response (RVR) varies widely, and evidence regarding its effect on time to heart rate control is limited. This study aims to evaluate whether early initiation of scheduled oral diltiazem therapy, in addition to continuous IV infusion, improves time to effective heart rate control compared with IV infusion alone.

This single-center, retrospective cohort study includes patients aged ≥18 years who presented to the ED in AF/AFL with RVR and were treated with IV diltiazem from January 1, 2021 to August 31, 2025. Patients who received scheduled oral diltiazem < 6 hours of diltiazem infusion initiation (early initiation) versus those receiving oral diltiazem ≥ 6 hours from infusion initiation (standard care) will be compared. The primary outcome is time to effective heart rate control, defined as heart rate < 110 beats/min sustained over a minimum of 1-hour. Secondary outcomes include length of stay, duration of diltiazem infusion, need for additional IV diltiazem, and heart rate at hospital discharge. Safety outcomes include incidence of hypotension, bradycardia, heart block, and new vasopressor requirements. Descriptive statistics will be used for demographic data, and appropriate statistical analyses will be applied based on whether data is categorical or continuous.

From preliminary data review, a total of 20 patients have been screened, of which 25% (n = 5) met inclusion. Of the 15 patients excluded, 67% (n = 10) were excluded for the presence of acute contributing conditions (e.g. sepsis). The median age of included patients was 70 years old. Of those included, 4 had no prior history of AF/AFL. All 5 patients included thus far are in the standard care group. The median number of IV diltiazem boluses received was 2 and the median duration of diltiazem infusion was 40.1 hours. The median time to heart rate control was 27.8 hours. Three patients experienced at least one of the safety outcomes listed above.

This study will provide insight into the impact of early oral diltiazem administered with IV infusion on achieving heart rate control in patients with AF/AFL and RVR. Final results to be presented.