SAFETY AND EFFICACY OF INTRAVENOUS DILTIAZEM IN ATRIAL-FIBRILLATION OR ATRIAL-FLUTTER

This study examines the efficacy of various doses of intravenous dilti azem to control the ventricular response during atrial fibrillation or atrial flutter. Control of the ventricular response of patients with atrial fibrillation and a rapid ventricular response can provide patie nts with relief of symptoms and improve hemodynamics. Eighty-four cons ecutive patients with atrial fibrillation or atrial flutter, or both, received an intravenous bolus dose of diltiazem followed by a continuo us infusion of diltiazem at 5, 10, and 15 mg/hour. The mean ventricula r response and blood pressure were monitored. Overall, 94% of patients (79 of 84) responded to the bolus dose with a >20% reduction in heart rate from baseline, a conversion to sinus rhythm, or a heart rate <10 0 beats/min. Seventy-eight patients received the continuous infusion. After 10 hours of infusion, 47% of patients (confidence interval [CI]: 36%, 59%) had maintained response with the 5 mg/hour infusion, 68% (C I: 57%, 79%) maintained response after the infusion was titrated to 10 mg/hour, and 76% (CI: 66%, 85%) after titration from the 5 and 10 mg/ hour infusion to the 15 mg/hour dose. For the 3 diltiazem infusions st udied, mean (+/- SD) heart rate was reduced from a baseline value of 1 44 +/- 14 beats/min to 98 +/- 19, 107 +/- 25, 107 +/- 22, 101 +/- 22, 91 +/- 17, and 88 +/- 18 beats/min at infusion times 0, 1, 2, 4, 8, an d 10 hours, respectively. By the end of the infusion, 18% of patients (14 of 78) had conversion to sinus rhythm. Hypotension was the most co mmon side effect, occurring in 13% of patients. Symptomatic hypotensio n was present in 3.6% of patients, and responded to normal saline solu tion in all cases. We conclude that a bolus dose of 20 or 25 mg follow ed by titration of a continuous infusion of 5, 10, and 15 mg/hour of i ntravenous diltiazem is a safe and effective regimen to rapidly lower heart rate in patients with atrial fibrillation and atrial flutter.