Amiodarone versus diltiazem for rate control in critically ill patients with atrial tachyarrhythmias

Objective: To compare the rate-lowering effect of diltiazem and two amiodarone regimens in critically ill patients with recent-onset atrial tachyarrhythmias. Design: Prospective, randomized, controlled study. Setting: Medical cardiologic intensive care unit in a university hospital. Patients: Sixty critically ill patients (Acute Physiology and Chronic Health Evaluation [APACHE] III score 70 +/- 30, age 67 +/- 10 yrs). Interventions: Patients with atrial fibrillation (n = 57), atrial flutter (n = 2), or atrial tachycardia (n = 1, and a heart rate consistently > 120 heats/min over 30 mins were randomly assigned to one of three intravenous treatment regimens. Group 1 received diltiazem in a 25-mg bolus followed by a continuous infusion of 20 mg/hr for 24 hrs, group 2 received amiodarone in a 300-mg bolus, and group 3 received amiodarone in a 300-mg bolus followed by 45 mg/hr for 24 hrs. Measurements and Main Results: The primary study end point was a > 30% rate reduction within 4 hrs. The secondary study end point was a heart rate < 120 beats/min (a patient was considered to have uncontrolled tachycardia if heart rate was > 120 beats/min 4 hrs after study drug). The primary study end point was achieved in 14/20 (70%), 11/20 (55%), and 15/20 (75%) of patients in groups 1, 2, and 3, respectively (chi (2) = 1.95, P = .38). Uncontrolled tachycardia was more frequently observed in group 2 (0/20, 9/29 [55%], and 1/20 [5%] of patients in groups 1, 2, and 3, respectively; chi (2) = 17, p = .00016). In patients achieving tachycardia control, diltiazem showed a significantly better rate reduction (p =.0001 group 1 vs. group 3, p =.0001 over time; p =.0001 group 1 vs. group 2, p = .001 over time) when compared with the amiodarone groups. Premature drug discontinuation due to hypotension was required significantly more often in group 1 (6/20 [30%], 0/20, and 1/20 [5%] for groups 1, 2, and 3, respectively; chi (2) = 10, p = .01). Conclusion: Sufficient rate control can be achieved in critically ill patients with atrial tachyarrhythmias using either diltiazem or amiodarone. Although diltiazem allowed for significantly better 24-hr heart rate control, this effect was offset by a significantly higher incidence of hypotension requiring discontinuation of the drug. Amiodarone may be an alternative in patients with severe hemodynamic compromise.