Study objectives: To compare the efficacy and safety of intravenous diltiazem and verapamil in controlling ventricular rate in patients with atrial fibrillation or flutter, and to evaluate the effects of these agents on left ventricular systolic function.
Design: Prospective, randomized, double-blind, crossover study.
Setting: University-affiliated hospital and Veterans Administration hospital.
Patients: Seventeen men with atrial fibrillation or flutter with a ventricular rate of 120 beats/minute or higher and a systolic blood pressure of 100 mm Hg or greater.
Interventions: Patients received up to two intravenous boluses of either diltiazem or verapamil, followed by an 8-hour continuous infusion if a therapeutic response was achieved (phase I). After a washout period, patients who responded were crossed over to receive the other drug in a similar fashion (phase II).
Measurements and main results: At the end of each infusion, the patient's ejection fraction was assessed by gated angiography. Of the 17 men initially randomized, 8 successfully completed both phases I and II. In these patients, baseline mean (+/- SD) ventricular rates before treatment with intravenous diltiazem and verapamil were 138 +/- 15 and 132 +/- 9 beats/minute, respectively (NS). At 2 minutes after the initial bolus dose, the mean ventricular rate decreased to 100 +/- 13 beats/minute in the diltiazem group compared with 114 +/- 17 beats/minute in those receiving verapamil (p < 0.05). Mean ventricular rates of 96 +/- 11 and 97 +/- 9 beats/minute were maintained during the 8-hour continuous infusion of diltiazem and verapamil, respectively (NS). On completion of the bolus dose(s) and during continuous infusions, there were no significant differences in blood pressures between the groups. Mean ejection fractions were 35.6 +/- 13.6% and 35.5 +/- 15.4% in the diltiazem and verapamil groups, respectively (NS). For the 17 patients, the mean maximum percentage decreases in blood pressure were not significantly different between groups. However, three patients developed symptomatic hypotension, all of whom were randomized to receive verapamil initially.
Conclusion: Intravenous diltiazem and verapamil are comparable in terms of efficacy and effect on systolic function in patients with rapid atrial fibrillation and flutter. However, hypotension may limit therapy with verapamil in some patients.