CONTROL OF HEART-RATE DURING TRANSITION FROM INTRAVENOUS OF ORAL DILTIAZEM IN FIBRILLATION OR FLUTTER

We tested whether patients presenting with atrial fibrillation (AF) or flutter (AFI) with a rapid ventricular response could maintain contro l of heart rate while transferring from a bolus and continuous infusio n of intravenous diltiazem to oral diltiazem. Forty patients with AF o r AFI and sustained ventricular rate greater than or equal to 120 beat s/min received intravenous diltiazem ''bolus'' (20 to 25 mg for 2 minu tes) and ''infusion'' (5 to 15 mg/hour for 6 to 20 hours). Oral long-a cting diltiazem (diltiazem CD 180, 300, or 360 mg/24 hours) was admini stered in patients in whom stable heart rate control was attained duri ng constant infusion. Intravenous diltiazem infusion was discontinued 4 hours after the first oral dose, and patients were monitored during 48 subsequent hours of ''transition'' to oral therapy. Response to dil tiazem was defined as heart rate <100 beats/min, greater than or equal to 20% decrease in heart hate from baseline, or con version to sinus rhythm. Other rate control or antiarrhythmic medications were slot all owed during the study period. Thirty-seven of 40 patients maintained h eart rate control during the bolus, and 35 of the remaining 37 maintai ned control during the infusion of intravenous diltiazem. Of the 35 pa tients achieving heart rate control with intravenous diltiazem who ent ered the transition to oral therapy, 27 maintained heart rate control (response rate of 77%, 95% confidence interval 63% to 91%). The median infusion rate of intravenous diltiazem was 10 mg/hour, and the median dose of oral diltiazem CD was 300 mg/day. Oral long-acting diltiazem was 77% effective in controlling ventricular response over 48 hours in patients with AF or AFI in whom ventricular response was initially co ntrolled with intravenous diltiazem. (C) 1996 by Excerpta Medica, Inc.