Emergency Medical Services
The use of diltiazem for treating rapid atrial fibrillation in the out-of-hospital setting*

Presented at the Society for Academic Emergency Medicine Mid-Atlantic Regional Conference, York, PA, April 2000, and at the Society for Academic Emergency Medicine annual meeting, San Francisco, CA, May 2000.
https://doi.org/10.1067/mem.2001.111518Get rights and content

Abstract

Study Objective: We sought to evaluate the use of intravenous diltiazem for treatment of rapid atrial fibrillation or flutter (RAF) in the out-of-hospital setting. Methods: This study is a retrospective review of data with historical control subjects. Data were drawn from out-of-hospital patients reported to a statewide paramedic system who presented with atrial fibrillation or flutter and a ventricular response rate (VRR) of 150 beats/min or greater. The intervention (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 cardioversion were omitted. Therapeutic response was defined as the occurrence of change to sinus rhythm, reduction of VRR to 100 beats/min or less, or reduction of baseline VRR by 20% or greater. Data were analyzed by using the χ2 test, the Student’s t test, and odds ratios (ORs). A Bonferroni adjusted P value of.005 was used to define statistical significance. Results: Forty-three patients receiving diltiazem and 27 control subjects were included in the study. The mean total diltiazem dose was 19.8 mg (95% confidence interval 17.8 to 21.8). The diltiazem and control groups did not significantly differ with respect to age; sex; history of atrial fibrillation; prior use of digitalis, β-blockers, or calcium channel blockers; concurrent 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 difference was statistically significant (P <.001). The mean percentage reduction of VRR in the diltiazem group was –33.1%. The difference in systolic blood pressure change between the diltiazem and control groups was not statistically significant (P =.17). The diltiazem group had a higher prevalence of achieving VRR reduction to 100 beats/min or less than did the control group (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, endotracheal intubation, resuscitation from cardiac arrest, or emergency treatment of unstable dysrhythmias. Conclusion: The effects of diltiazem on RAF can be appreciated within the constraints of the out-of-hospital environment. Diltiazem should be considered as a viable field therapy for rate control of RAF. [Wang HE, O’Connor RE, Megargel RE, Schnyder ME, Morrison DM, Barnes TA, Fitzkee A. The use of diltiazem for treating rapid atrial fibrillation in the out-of-hospital setting. Ann Emerg Med. January 2001;37:38-45.]

Introduction

Atrial fibrillation (AF) is a common dysrhythmia encountered in clinical practice, with a prevalence in the United States ranging from 2.3% in persons older than 40 years to 5.9% in persons older than 65 years.1, 2 Uncontrolled or rapid AF (RAF; atrial fibrillation with an accelerated ventricular response rate [VRR]) can result in impaired diastolic filling, loss of atrial kick, decreased ventricular output, and decreased coronary perfusion. The priority in managing RAF is control of ventricular rate.1, 3, 4 Pharmacologic agents, such as digitalis, β-blockers, calcium channel blockers, and other antiarrhythmic agents, are commonly used for controlling RAF.3, 4, 5, 6, 7, 8

Diltiazem hydrochloride is a commonly used calcium ion channel inhibitor. Diltiazem slows atrioventricular (AV) nodal conduction, prolongs the AV nodal refractory period, and is useful for ventricular rate control of AF.4, 9, 10, 11 Intravenous diltiazem has been demonstrated as an effective treatment for RAF and is widely used in contemporary emergency medicine practice.12, 13, 14 The out-of-hospital use of diltiazem has been relatively limited because of difficulties with field storage of the drug; the original solution requires refrigerated storage at 2°C to 8°C (35.6°F to 46.4°F).15 However, the introduction of lyophilized diltiazem has permitted the storage and use of diltiazem under field conditions. This system uses a dual-chamber syringe containing lyophilized diltiazem powder and a benzyl alcohol–based diluent and may be stored at 15°C to 30°C (59°F to 86°F).9 There have been few reports of diltiazem use in the out-of-hospital setting for RAF.15, 16 The purpose of this study was to evaluate the utility and safety of intravenous diltiazem for treating RAF within the clinical constraints of out-of-hospital care.

Section snippets

Materials and methods

This study is a retrospective review with historic control subjects. Data were drawn from out-of-hospital charts for 3 county-based paramedic systems. Each system is autonomous but operates by using statewide standing orders for patient care. Each system uses 2-person paramedic units, and a total of 15 units (plus supervisor units) serves the state at any given time. The 3 systems serve a population of approximately 745,000 in urban, suburban, and rural settings. All paramedics are trained in

Results

For the intervention period, there were 17,048 patient contacts, with administration of diltiazem identified in 50 cases. Six patients were omitted because the underlying rhythm was PSVT, and 1 was omitted because of inadequate documentation, resulting in a total of 43 subjects in the diltiazem group. No patients receiving diltiazem required exclusion because of intubation, cardioversion, or resuscitation from cardiac arrest. For the control period, there were 25,924 patient contacts, resulting

Discussion

The morbidity associated with AF is attributed to excessive ventricular rate, syncope after cessation of AF, systemic embolization, loss of atrial contribution to cardiac output, and anxiety from palpitations.23 The clinical approach to AF in the ED depends on the condition of the patient. In the setting of a clinically compromised patient, urgent cardioversion is usually indicated.3, 6, 23, 24 Patients who have AF with a rapid VRR but who are clinically stable may benefit from a short trial of

Acknowledgements

We thank Musa Nsereko, BDS, MPH, Statistician, Performance Improvement Department, Christiana Care Health System, for his assistance with the statistical analysis for this study.

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    *

    Address for reprints: Henry E. Wang, MD, Department of Emergency Medicine, University of Pittsburgh School of Medicine, 230 McKee Place, Suite 400, Pittsburgh, PA 15213; 412-303-7793, 412-647-4925; E-mail [email protected].

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