Intravenous diltiazem for the treatment of patients with atrial fibrillation or flutter and moderate to severe congestive heart failure

The objective of this multicenter, randomized, double-blind, placebo-controlled study was to determine the safety and efficacy of intravenous diltiazem in the treatment of 37 patients with rapid (ventricular rate, mean ± SD 142 ± 17 beats/min) atrial fibrillation or flutter and moderate to severe congestive heart failure (ejection fraction, mean ± SD 36 ± 14%; New York Heart Association class III [23 patients], class IV [14 patients]). During the double-blind portion of the study, patients received either intravenous diltiazem, 0.25 mg/kg over 2 minutes, or placebo followed 15 minutes later by diltiazem or placebo, 0.35 mg/kg over 2 minutes, if the first dose was tolerated but ineffective. Placebo nonresponders were given open-label intravenous diltiazem in a similar fashion as in the double-blind portion of the study. In the double-blind part of the study, 21 (18 with 0.25 mg/kg, 3 with an additional 0.35 mg/kg) of the 22 patients (95%) responded to diltiazem, and 0 of 15 patients (0%) responded to placebo (p < 0.001). All 15 patients (13 with 0.25 mg/kg and 2 with an additional 0.35 mg/kg) who received placebo during the double-blind period had a therapeutic response to diltiazem during open-label therapy. Overall, 36 of 37 patients (97%) had a therapeutic response to intravenous diltiazem. Heart rate response to diltiazem after the 2-minute bolus infusions consisted of a ≥20% decrease in heart rate from baseline in 36 patients; in addition, 17 patients also had heart rates decreased to <100 beats/min, whereas no patient had conversion to sinus rhythm. The median time to response from the beginning of the 2-minute bolus dose of diltiazem was about 5 minutes. Hypotension was the most common adverse event occurring in 4 of the 37 patients (11%). No patient had an exacerbation of congestive heart failure due to diltiazem. In conclusion, intravenous diltiazem is rapid, safe, and effective in acutely lowering a rapid ventricular rate in patients with atrial fibrillation or flutter and moderate to severe congestive heart failure.