The use of diltiazem for treating rapid atrial fibrillation in the out-of-hospital setting

Study objective: We sought to evaluate the use of intravenous diltiazem for treatment of rapid atrial fibrillation or flutter (RAF) in the out-of-hosp ital setting. Methods: This study is a retrospective review of data with historical contr ol subjects. Data were drawn from out-of-hospital patients reported to a st atewide paramedic system who presented with atrial fibrillation or flutter and a ventricular response rate (VRR) of 150 beats/min or greater. The inte rvention (diltiazem) group included patients who received diltiazem during a 9-month period in 1999. The control group included patients from 1998 who did not receive diltiazem. Patients who were intubated or underwent cardio version were omitted. Therapeutic response was defined as the occurrence of change to sinus rhythm, reduction of VRR to 100 beats/min or less, or redu ction of baseline VRR by 20% or greater. Data were analyzed by using the ch i (2) test, the Student's t test, and odds ratios (ORs). A Bonferroni adjus ted P value of .005 was used to define statistical significance. Results: Forty-three patients receiving diltiazem and 27 control subjects w ere included in the study. The mean total diltiazem dose was 19.8 mg (95% c onfidence interval 17.8 to 21.8). The diltiazem and control groups did not significantly differ with respect to age; sex; history of atrial fibrillati on; prior use of digitalis, P-blockers, or calcium channel blockers; concur rent out-of-hospital therapies; or baseline VRR or systolic blood pressure (P=.09 to 1.00). The difference in VRR reduction between the diltiazem and control groups was 38 beats/min (95% confidence interval 24 to 52); this di fference was statistically significant (P<.001). The mean percentage reduct ion of VRR in the diltiazem group was -33.1%. The difference in systolic bl ood pressure change between the diltiazem and control groups was not statis tically significant (P=.17). The diltiazem group had a higher prevalence of achieving VRR reduction to 200 beats/min.or less than did the control grou p (OR 22.6; P<.001), of achieving a VRR reduction of 20% or greater (OR 19. 3; P<.001), and of achieving overall therapeutic response (OR 19.3; P<.001) . Few changed to sinus rhythm in either group (estimated OR 6.3; P=.15). No patients in the diltiazem group required treatment for hypotension, endotr acheal intubation, resuscitation from cardiac arrest, or emergency treatmen t of unstable dysrhythmias. Conclusion: The effects of diltiazem on RAF can be appreciated within the c onstraints of the out-of-hospital environment. Diltiazem should be consider ed as a viable field therapy for rate control of RAF.