Electrical cardioversion of emergency department patients with atrial fibrillation

Electrical cardioversion of emergency department patients with atrial fibrillation

CARDIOLOGY/ORIGINAL RESEARCH Electrical Cardioversion of Emergency Department Patients With Atrial Fibrillation John H. Burton, MD David R. Vinson, ...

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CARDIOLOGY/ORIGINAL RESEARCH

Electrical Cardioversion of Emergency Department Patients With Atrial Fibrillation

John H. Burton, MD David R. Vinson, MD Kate Drummond, MD Tania D. Strout, RN Henry C. Thode, PhD Jeff J. McInturff, MD From the Department of Emergency Medicine, Maine Medical Center, Portland, ME (Burton, Drummond, Strout); the Department of Emergency Medicine, Kaiser Permanente Medical Centers, Sacramento and Roseville, CA (Vinson, McInturff); and the Department of Emergency Medicine, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, NY (Thode).

Study objective: Electrical cardioversion of emergency department (ED) patients with atrial fibrillation has not been well investigated. The objective of this study is to identify the outcomes and complications associated with ED electrical cardioversion of patients with atrial fibrillation. Methods: This retrospective health records survey investigated a consecutive cohort of ED patients with atrial fibrillation who underwent electrical cardioversion in 4 EDs during a 42-month period. Trained personnel reviewed medical records for demographic characteristics, clinical descriptors, medical interventions, complications, and ED return visits within 7 days. Data were analyzed using descriptive statistics. Results: The study population consisted of 388 patients (mean age 61 years; range 20 to 93 years). Duration of atrial fibrillation was less than 48 hours in 99% of the cohort. Electrical cardioversion was successful in 332 (86%) patients. Twenty-eight complications were noted in 25 electrical cardioversion encounters: 22 attributed to procedural sedation and analgesia and 6 attributed to electrical cardioversion. Three hundred thirty-three (86%) patients were discharged to home from the ED: 301 after electrical cardioversion success and 32 with electrical cardioversion failure. Thirtynine patients (10%) returned to the ED within 7 days, 25 of these patients (6% of successful electrical cardioversion patients) returned because of relapse of atrial fibrillation. Conclusion: In this multicenter cohort, selected ED patients with atrial fibrillation had high rates of electrical cardioversion success, infrequent hospital admission, and few immediate and short-term complications. [Ann Emerg Med. 2004;44:20-30.]

0196-0644/$30.00 Copyright Ó 2004 by the American College of Emergency Physicians. doi:10.1016/ j.annemergmed.2004.02.016

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Editor’s Capsule Summary What is already known on this topic Many stable patients with atrial fibrillation are admitted to an inpatient setting for the express purpose of electrically cardioverting to restore normal sinus rhythm. What question this study addressed This study examined the safety and efficacy of emergency department (ED)–based electrical cardioversion for selected patients with atrial fibrillation. What this study adds to our knowledge This study demonstrated an 86% success rate of electrical cardioversion in 388 ED patients with atrial fibrillation of less than 48 hours duration. Complications occurred in about 6% and were usually the result of procedural sedation. Only 6% of successfully cardioverted patients returned to the ED within 7 days for recurrent atrial fibrillation. How this might change clinical practice Elective cardioversion in the ED for carefully selected patients with atrial fibrillation has a high success rate, relatively few complications, and a low rate of returning to the ED within one week. If confirmed in other studies, this might lead to a decreasing need to admit such patients as inpatients.

INTRODUCTION

Approximately 0.4% of the US population is afflicted with atrial fibrillation.1 These individuals represent a diverse population, including all races, both sexes, and a wide range of ages. Because of the prevalence of this disease, the burden of atrial fibrillation on medical costs and hospital visits remains high, with likely escalation in the foreseeable future.1,2 Atrial fibrillation is the most common sustained cardiac arrhythmia, as well as the most common arrhythmia in the emergency department (ED) setting.3-5 As a consequence, atrial fibrillation–related ED encounters are frequent. Many investigations and guidelines have discussed the acute treatment of patients with atrial fibrillation.6-11 The majority of these investigations and guidelines describe various management options and the attendant success rates of rate control and pharmacologic cardioversion. Guidelines for atrial fibrillation management have identified electrical cardioversion as an option in the ED for stable and unstable atrial fibrillation patients.8,9,11 For stable patients with an atrial fibrillation episode duration of less than 48 hours, a low risk of intracardiac thrombus formation and thromboembolism is cited in support of rhythm cardioversion without antecedent anticoagulation.7-14 The prevalence, effectiveness, and safety of electrical cardioversion as an ED atrial fibrillation management

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strategy for patients with recent-onset atrial fibrillation have not been well described. Few investigators have addressed the experience of ED electrical cardioversion in atrial fibrillation patients who are deemed clinically stable.1,15 The objective of this study is to describe the population, outcomes, and short-term complications associated with ED electrical cardioversion of a large group of clinically stable atrial fibrillation patients. MATERIALS AND METHODS Theoretical Model of the Problem

Atrial fibrillation is the most common sustained arrhythmia in patients presenting to the ED.3-5 Many investigations and guidelines have discussed the acute management of atrial fibrillation in this setting with electrical cardioversion as an option for the symptomatic, stable patient with recent-onset atrial fibrillation.6-11 We sought to describe a large cohort of ED atrial fibrillation patients who underwent ED electrical cardioversion in preference to other commonly used management strategies, including chemical cardioversion, rate control, and patient admission to hospital. Study Design

This retrospective health records survey investigated a consecutive cohort of clinically stable atrial fibrillation patients who underwent ED electrical cardioversion in 4 institutions during a 42-month period from October 1998 through March 2002. The institutional review board at each participating medical center approved the study protocol and data forms. Setting

Three of the 4 investigation sites are suburban community hospitals that are part of a large group-model health maintenance organization. The fourth site is an urban tertiary-care hospital. The 4 EDs are staffed by boardcertified or residency-trained, board-prepared emergency physicians. One ED serves as the primary training location for an emergency medicine residency program, whereas 2 other sites are affiliated with an emergency medicine residency program. The approximate mean annual censuses at the investigation sites during the study period ranged from 33,000 to 52,000 patient visits. Selection of Participants

ED patients evaluated for atrial fibrillation during the study period were identified by query of hospital

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databases at each institution. These databases identified potential study subjects through International Classification of Diseases, Ninth Revision, Clinical Modification (ICD9-CM) coding for hospital billing and discharge records. Separate queries undertaken through ED quality review records identified patients during the study period who underwent procedural sedation and analgesia. This list was reviewed for patients who underwent procedural sedation and analgesia for atrial fibrillation electrical cardioversion. Combining these 2 groups for each site derived the final study subject cohort. An additional cohort was reviewed at one investigational site (Maine Medical Center, Portland, ME). This cohort included patients who underwent either an ED atrial fibrillation chemical cardioversion attempt or patients who had an ED atrial fibrillation pharmacologic intervention (eg, rate control) that did not include chemical or electrical cardioversion. Methods of Measurement

Trained personnel at each study site reviewed the identified medical records for variables that included demographic characteristics, clinical descriptors, medical interventions, complications, and ED return visits. Patients who underwent ED electrical cardioversion for clinically unstable atrial fibrillation were excluded from the investigational cohort. An unstable patient was defined as any ED patient who underwent emergency electrical cardioversion because of ischemic chest pain, shortness of breath, decreased level of consciousness, hypotension, shock, pulmonary congestion, congestive heart failure, or acute myocardial infarction.6 Before abstraction of patient information, study variables were explicitly defined, and a standardized data collection instrument was designed. The medical records pertaining to each ED electrical cardioversion were reviewed by 1 of 3 trained abstractors who worked independently. Interrater reliability between abstractors was assessed by a weighted k statistic for a random set of 50 cardioversion patients. Abstracted clinical information included the duration of the atrial fibrillation episode and the presence or absence of common ED atrial fibrillation chief complaints (eg, chest pain, palpitations, shortness of breath). Historical components included history of previous atrial fibrillation episodes, medical history, atrial fibrillation risk factors, and current anti-arrhythmic and anticoagulant medications. For patients with a history of atrial fibrillation episodes, records were reviewed for previous atrial fibrillation–related interventions and management.

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Physical assessment elements included vital signs during the ED management course, including systolic blood pressure, pulse rate, respiratory rate, and hemoglobin oxygen saturation assessments. Diagnostic testing elements included 12-lead ECG interpretation by the examining emergency physician. ED atrial fibrillation interventions included rate-slowing pharmacotherapy. The medications used, their dosing, and the successes of each rate-slowing intervention were abstracted. Rate control success was explicitly defined as achieving a sustained pulse rate below 120 beats/min within one hour of the medication administration.1 Success of chemical or electrical cardioversion interventions was defined as a return to sinus rhythm, as demonstrated on a rhythm strip and 12-lead ECG and sustained through ED discharge. Each atrial fibrillation medication or intervention was reviewed for predefined adverse events. These complications included vital sign changes (pulse rate <50 beats/min, systolic blood pressure <90 mm Hg, hemoglobin oxygen saturation <90%, apnea), acute allergic reactions, nausea, emesis, cardiac dysrhythmia (other than atrial fibrillation or sinus rhythm), and changes in physical examination results or assessment suggestive of thromboembolic complications. For any adverse event, records were reviewed for the consequent treatment rendered and effect on further treatment or patient disposition (eg, ICU admission or discharge). For ED electrical cardioversion procedures, data abstracted included the type of external, direct-current waveform used (monophasic or biphasic), the number of shocks, the magnitude of the energy settings for each patient, and the patient disposition after the procedure.16 Medical records were reviewed for complications inherent to the direct-current shock, specifically chest wall burns or skin irritation at the electrode patch or paddle site. Additional data abstracted for the electrical cardioversion procedures included analgesic and sedative agents used for procedural sedation and analgesia, as well as the complications associated with the use of these agents, including vital sign changes (as defined above), use of bagvalve-mask device for assisted ventilation, nausea, emesis, and agitation. The involvement of non–emergency physician consultants in each patient’s care was also noted from the medical record. Telephone and paging logbooks were not reviewed in the respective EDs for consultant contacts and involvement. To address short-term complications, each study site was queried for patient returns for clinical care at the respective ED site within 7 days of the electrical cardioversion attempt. Data elements included reason for return, recurrence of atrial

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fibrillation, and complications related to the index ED visit. During the investigational period, all study sites used regional procedural sedation and analgesia guidelines specific to each ED. These guidelines specify that emergency nurses, emergency physicians, and consultants trained and certified for procedural sedation and analgesia at each institution may perform procedural sedation and analgesia in the ED. These guidelines mandate a procedural sedation and analgesia physician and nurse presence during all procedural sedation and analgesia events and procedures with standardized patient respiratory and hemodynamic monitoring. The selection and dose of the procedural sedation and analgesia agent(s) used for the ED procedure are chosen at the discretion of the procedural sedation and analgesia physician. No standardized atrial fibrillation pathway or protocol was present at the participating EDs during the investigational period. The approach and treatment of the atrial fibrillation patient at each institution was based on the discretion and interaction between the patient, the attending emergency physician, and any consultant who may have participated in the patient’s ED care. The following were decisions that varied with each patient encounter: the use, selection, and dose of rate-slowing agents; the use, selection, and dose of chemical cardioversion agents; the drug and amount of procedural sedation and analgesia agents; and the energy and number of electrical cardioversion attempts. Waveform selection was typically based on availability of the electrical cardioversion device within the ED, with availability of biphasic waveform devices increasing toward the end of the study period.

range 20 to 93 years) from a total of 3,686 ED atrial fibrillation encounters during the investigational period (Figure). Interrater reliability between abstractors demonstrated excellent agreement with weighted k ranging from 0.739 to 1.0 for 5 outcome measures: previous episodes of atrial fibrillation, cardioversion success, patient disposition, procedural sedation agent used, and cardioversion complications. Two patients underwent emergency electrical cardioversion when deemed medically unstable by the health care providers. Both of these patients were hypotensive, with approximate systolic blood pressures of 70 mm Hg at their evaluation. Neither patient received procedural sedation and analgesia for the electrical cardioversion procedure. The demographic findings of the 388 stable atrial fibrillation patients treated with ED electrical cardioversion (at all 4 institutions) are compared with those of patients treated without electrical cardioversion (either chemical cardioversion alone or no attempt at cardioversion) at a single institution in Table 1.

Figure. ED atrial fibrillation encounters and ED electrical cardioversion procedures at study institutions during the investigational period, October 1998 to March 2002. *Unstable patient defined as patient cardioverted urgently in the ED because of chest pain, shortness of breath, decreased level of consciousness, hypotension, shock, pulmonary congestion, congestive heart failure, or acute myocardial infarction.6 Tele, Telemetry/ cardiac-monitored hospital bed; ICU, ICU hospital bed.

Primary Data Analysis

Microsoft Excel 97 (Microsoft Corporation, Redmond, WA) was used for data entry and simple descriptive statistics. Additional statistical analysis was conducted using SPSS software (version 11.0, SPSS, Inc., Chicago, IL). Descriptive statistics for continuous variables were presented using means and SDs. Categoric variables were presented as the percentage of the occurrence frequency.

RESULTS Characteristics of Study Subjects

The study population consisted of 388 electrical cardioversion patient encounters (mean age 61613 years;

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Main Results

The success rate for chemical cardioversion of atrial fibrillation at one institution during the study period was 17%. Four patients were successfully cardioverted with ibutilide, and one patient was successfully cardioverted with procainamide. In the group that failed chemical cardioversion, 9 patients received ibutilide, 10 patients received procainamide, and 2 patients received flecainide, sotalol, and amiodarone. This group of 30 patients had 6 reported complications among 6 different patients: 4 hypotensive episodes (all responded to intravenous fluid management) and 2 bradycardic events. The demographic findings of the 388 stable atrial fibrillation patients treated with ED electrical cardiover-

sion, as well as the presence of these characteristics within each group according to the success or failure of the cardioversion procedure, are shown in Table 2. The duration of atrial fibrillation was less than 48 hours in 381 patient encounters (99% of the cohort). The duration of atrial fibrillation was unknown or not documented in 5 patient encounters. Two patients underwent an electrical cardioversion procedure, with duration of atrial fibrillation greater than 48 hours. Both patients were between 50 and 60 years old, had a history of infrequent paroxysmal atrial fibrillation, and were receiving therapeutic doses of warfarin. Both underwent successful electrical cardioversion without complications and were discharged to home.

Table 1.

Baseline characteristics and sinus rhythm conversion for ED atrial fibrillation patients treated with electrical cardioversion compared with ED atrial fibrillation patients at one study site who received a chemical cardioversion attempt or patients who were treated for atrial fibrillation (eg, rate control) but received neither a chemical or electrical cardioversion attempt.

Characteristic Mean age, y6SD Male sex, No. (%) Chief complaint, No. (%) Palpitations Chest pain Shortness of breath Dizziness Syncope Other/unspecified Medical history, No. (%) Previous atrial fibrillation episode(s) Hypertension Coronary artery disease Thromboembolic disease Thyroid disease Valvular heart disease Congestive heart failure Chronic lung disease Medications, No. (%) Antiarrhythmics Coumadin b-Blockers Calcium channel blockers Digoxin Previous atrial fibrillation episode with successful cardioversion, No. (%) Chemical Electrical Duration (in hours) of current atrial fibrillation episode, No. (%) 1–5 6–12 13–24 25–48 >48 Not documented Cardioversion to sinus rhythm during ED visit

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Chemical Cardioversion (n=30)

No Chemical or Electrical Cardioversion (n=266)

61613 212 (55)

68616 19 (63)

68616 104 (39)

300 45 23 11 4 5

(77) (12) (6) (3) (1) (1)

25 (83) 3 (10) 0 (0) 2 (7) 0 0

106 63 33 16 9 39

(40) (24) (12) (6) (3) (15)

280 167 57 12 51 31 47 23

(72) (43) (15) (3) (13) (8) (12) (6)

23 10 8 1 1 2 1 2

(77) (33) (27) (3) (3) (7) (3) (7)

139 143 92 23 54 31 24 72

(52) (54) (35) (7) (20) (12) (9) (27)

124 74 81 52 45

(32) (19) (21) (13) (12)

4 4 14 3 7

(13) (13) (47) (10) (23)

22 49 101 52 34

(8) (18) (38) (20) (13)

Electrical Cardioversion (n=388)

41 (11) 166 (43) 186 100 61 34 2 5 332

(48) (26) (16) (9) (1) (1) (86)

8 (27) 3 (10) 18 (60) 8 (27) 2 (7) 1 (3) 1 (3) 0 5 (17)

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21 (8) 20 (8) 145 34 11 6 33 37 44

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Patient record documentation revealed use of consultants in 94 (24.2%) patients. The consultants involved were cardiologists in 85 encounters and internal medicine or family medicine physicians in 9 encounters. One hundred forty-two (37%) patients underwent rate-control intervention(s) before the electrical cardioversion procedure. Drugs used as the initial rateslowing agent included diltiazem (121 patients), metoprolol (10 patients), verapamil (5 patients), and digoxin (6 patients). Fifty-three patients received an additional dose or multiple doses of these medications after the initial rate-control drug. Success of the ED electrical

cardioversion stratified by antecedent rate-slowing (successful, unsuccessful, and none) is shown in Table 3. Two patients received adenosine during their ED stay before the electrical cardioversion procedure. Forty-seven patients received intravenous magnesium before the electrical cardioversion procedure. Twenty-five of the patients who received ibutilide concomitantly received magnesium. Successful electrical cardioversion occurred in 40 (85%) magnesium-treated patients. One hundred eleven (29%) patients underwent a chemical cardioversion attempt before the electrical cardioversion procedure. Pharmacologic cardioversion

Table 2.

Baseline characteristics of ED atrial fibrillation patients treated with electrical cardioversion according to success of cardioversion procedure.

Characteristic Mean age, y6SD Male sex, No. (%) Chief complaint in ED, No. (%) Palpitations Chest pain Shortness of breath Dizziness Syncope Other/unspecified Medical history, No. (%) Previous atrial fibrillation episode(s) Hypertension Coronary artery disease Thromboembolic disease Thyroid disease Valvular heart disease Congestive heart failure Chronic lung disease Medications, No. (%) Antiarrhythmics Coumadin b-Blockers Calcium channel blockers Digoxin Previous atrial fibrillation episode with successful cardioversion, No. (%)* Chemical Electrical Duration (in hours) of current atrial fibrillation episode, No. (%)y 1–5 6–12 13–24 25–48 >48 Not documented Initial vital signs Mean pulse rate, beats/min6SD Mean systolic blood pressure (mm Hg6SD)

Total (n=388)

Successful Electrical Cardioversion (n=332)

Unsuccessful Electrical Cardioversion (n=56)

61613 212 (55)

61614 186 (56)

64611 26 (46)

300 45 23 11 4 5

(77) (12) (6) (3) (1) (1)

261 35 18 9 4 5

(79) (11) (5) (3) (1) (2)

39 (70) 10 (18) 5 (9) 2 (4) 0 0

280 167 57 12 51 31 47 23

(72) (43) (15) (3) (13) (8) (12) (6)

245 140 50 10 44 26 38 20

(74) (42) (15) (3) (13) (8) (11) (6)

35 27 7 2 7 5 9 3

(63) (48) (13) (4) (13) (9) (16) (5)

124 74 81 52 45

(32) (19) (21) (13) (12)

109 63 70 45 40

(33) (19) (21) (14) (12)

15 11 11 7 5

(27) (20) (20) (13) (9)

41 (11) 166 (43)

35 (11) 149 (45)

6 (11) 17 (30)

186 100 61 34 2 5

160 89 48 28 2 5

(48) (27) (15) (8) (1) (2)

26 (46) 11 (20) 13 (23) 6 (11) 0 0

118632 138629

121629 140626

(48) (26) (16) (9) (1) (1)

119631 138629

*Some patients reported previously successful chemical and electrical cardioversion. y Five patients had unknown or unreported duration of atrial fibrillation symptoms.

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agents used were ibutilide (71 patients), procainamide (38 patients), and amiodarone (2 patients). Success of the ED electrical cardioversion procedure for patients with a chemical cardioversion attempt before the procedure is shown in Table 3. The electrical cardioversion waveform was monophasic in 76% of patient encounters. There was no documentation of the waveform in 1 patient. An additional 3 patients had no energy settings recorded for electrical cardioversion. The initial electrical cardioversion energy setting, as well as the successful cardioversion energy setting (for those patients successfully cardioverted), is shown in Table 4. All patients received intravenous procedural sedation and analgesia before electrical cardioversion. Agents used for electrical cardioversion included methohexital (193 patients), etomidate (148 patients), midazolam (25 patients), propofol (13 patients), morphine (1 patient), and fentanyl (24 patients), with some patients receiving more than 1 agent. Twenty-two procedural sedation and analgesia–related complications were noted, including oxygen desaturation below 90% (12 patients: 9 methohexital, 1 etomidate, 1 midazolam, 1 propofol), use of bag-valvemask device (6 methohexital patients), emesis (1 midazolam patient), hypotension (1 methohexital patient), bradycardia (1 methohexital patient), and agitation (1 etomidate patient). Only 1 patient had a procedural sedation and analgesia–related complication that resulted in a change in disposition. This 77-year-old man was admitted for observation after he experienced orthostatic hypotension

Table 3.

ED atrial fibrillation intervention(s) preceding attempts at electrical cardioversion with number and percentage of patients successfully cardioverted with each characteristic.

Characteristic Rate-control attempt (%)* Successful rate control Unsuccessful rate control No rate-control attempt Chemical cardioversion attempt (%) Unsuccessful chemical cardioversion No chemical cardioversion attempt

Total (n=388)

Successful Electrical Cardioversion (n=332)

142 (37) 112 30 246 111 (29)

123 98 25 209

(87) (88) (83) (85)

111

100 (90)

277

232 (84)

*Success for pulse rate control defined as achieving and sustaining a pulse rate <120 beats/min within 1 hour of the receipt of rate-control agent.

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after successful electrical cardioversion. Before the cardioversion procedure, this patient had received verapamil for pulse rate control. The treating physicians attributed his orthostatic symptoms and findings to the intravenous verapamil and methohexital. For the 6 patients treated with bag-valve-mask–assisted ventilation during methohexital procedural sedation and analgesia, none were intubated or admitted to the hospital. Complications attributed to rate control, chemical cardioversion, and electrical cardioversion interventions are displayed in Table 5. All hypotension and bradycardia episodes resolved without intervention, with the exception of 1 patient treated with verapamil and methohexital, as noted previously. Disposition from the ED after ED intervention(s) is documented in the Figure. Complications and unscheduled or scheduled return ED visits within 7 days of the index visit were noted in 39 (10%) patients. Two patients returned to the clinic or the

Table 4.

Energy settings and waveform used during ED electrical cardioversion encounters. Waveform

Characteristic (%) Initial cardioversion energy setting, J, n=384* 30 50 75 100 120 150 200 300 360 Successful cardioversion energy setting, J, n=329* 30 50 75 100 120 150 200 300 360 Successful ED electrical cardioversion (%)

Monophasic (n=296) (76)

Biphasic (n=91) (24)

0 41 3 171 0 3 70 4 2

23 48 4 11 2 2 0 0 0

0 9 1 73 0 13 98 35 19 250 (84)

11 30 10 22 3 3 2 0 0 81 (89)

*Waveform and energy settings not documented for 1 patient; energy settings not documented for 1 biphasic and 2 monophasic encounters. The 1 undocumented and the 2 monophasic encounters were successfully cardioverted.

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ED for scheduled checks of burns to the skin. Twenty-five patients returned to the ED for relapse of atrial fibrillation. Of these, 20 patients had a successful electrical cardioversion procedure during the index ED encounter (6.2% of successful electrical cardioversion patients), and 5 had an unsuccessful ED electrical cardioversion procedure. An additional 12 patients returned to the ED for a new problem unrelated to atrial fibrillation or the ED electrical cardioversion visit.

cardioversion attempts with subsequent next-day followup for rhythm assessment is an option for acute-onset atrial fibrillation patients at low risk for complications, we did not evaluate this management strategy. The interpretation of immediate and short-term complications as a consequence of the ED atrial fibrillation treatment of patients in this cohort is limited. Our 1-week follow-up period was chosen to be consistent with a previous report.1 Pooled data from studies evaluating thromboembolic events after electrical cardioversion have demonstrated that approximately 98% of embolic episodes will occur within 10 days of the cardioversion procedure.17 We did not evaluate long-term complications, nor could we exclude the possibility that patients with complications received care in a setting different from the index visit ED. More comprehensive patient follow-up could have been ascertained had we extended our follow-up review period or included a more broad follow-up strategy, including review of clinic and personal physician visits. Long-term complication risk from electrical and pharmacologic atrial fibrillation cardioversion, particularly thromboembolic events, has been noted to occur as long as 2 weeks after the cardioversion procedure.7,12,17-21 The absence of thromboembolic complications observed in this cohort would not preclude the possibility that thromboembolic events occurred in this cohort during or beyond the investigational data. We did not examine the use of echocardiographic thrombus screening before the ED electrical cardioversion procedure. Other authors have suggested this practice as a means of stratifying patients with recent-onset

LIMITATIONS

Limitations of this ED atrial fibrillation investigation include the medical record review and identification methodology of patients. Given these limitations, we believe that these investigational data should serve as a hypothesis-generating contribution. Our findings should not be interpreted as an attempt to validate the practice of electrical cardioversion for selected ED atrial fibrillation patients. We did not include a multicenter comprehensive review of all patients presenting to the ED with atrial fibrillation, acute and chronic, during the study period. The investigational review was limited only to patients who underwent an ED intervention specifically for atrial fibrillation. Therefore, there were many patients, likely with chronic atrial fibrillation, who presented to the ED and had no intervention(s) and were not included in our analysis. Given this focused population, the entire ED atrial fibrillation population management during the investigational period is somewhat obscured. Although discharge from the ED after pulse rate control without

Table 5.

Complications from ED interventions for pulse rate control, pharmacologic cardioversion, and electrical cardioversion for atrial fibrillation among 388 electrical cardioversion patients. Intervention

No.

Bradycardia*

Hypotensiony

Ventricular Tachycardia

Prolong QTcz

Burn§

Pulse rate control Pharmacologic cardioversion Electrical cardioversion

142 111 388

1 1 1

5 2 0

0 3k 2{

0 1 0

0 0 3

*Bradycardia defined as pulse rate <50 beats/min. y Hypotension defined as systolic blood pressure <90 mm Hg. z Prolonged corrected QT interval. § Chest wall burn; all chest burns mild or minor and required no intervention in the ED or at follow-up. All 3 were monophasic waveform electrical cardioversion patients. k Short run of ventricular tachycardia; all resolved without intervention: 2 patients with ibutilide, 1 patient with procainamide; all patients discharged to home after successful electrical cardioversion. { One patient shocked into ventricular tachycardia on first shock; immediate second shock resulted in return to atrial fibrillation. Second patient shocked into ventricular tachycardia with third shock; resolved spontaneously with return to atrial fibrillation. Both patients admitted to ICU for observation, with uncomplicated hospital course.

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atrial fibrillation with regard to thromboembolic risk.22-24 DISCUSSION

In this multicenter cohort, selected ED atrial fibrillation patients who underwent electrical cardioversion had high rates of successful rhythm conversion and discharge to home, with few complications noted during the ED visit and within one week. The majority of complications attributed to the electrical cardioversion experience in these patients were related to procedural sedation and analgesia. There were no atrial fibrillation treatment protocols or pathways in place at the investigational institutions during the 42-month study period. During this time, approximately 10% of ED atrial fibrillation patients were determined by the examining clinicians to be candidates for an electrical cardioversion procedure. Review of our findings would suggest that patients deemed candidates for ED electrical cardioversion were patients primarily with a history of atrial fibrillation palpitations for less than 24 hours. Additionally, the majority of the cohort had a history of paroxysmal atrial fibrillation, with approximately half reporting a history of electrical or chemical cardioversion attempts. No randomized controlled trials have been published to support or refute the use of electrical cardioversion as an intervention in ED patients with recent-onset atrial fibrillation.25 However, a randomized, controlled, clinical trial was recently published that compared outcomes associated with either primary rhythm control or primary rate control in patients with long-standing atrial fibrillation (the Atrial Fibrillation Follow-up Investigation of Rhythm Management [AFFIRM] trial).26 Because our patient population differs from that of the AFFIRM trial, comparison between the trials must be limited. The AFFIRM investigation enrolled patients ‘‘. . . who were at least 65 years of age or who had other risk factors for stroke or death . . . [with] over-riding criteria for enrollment . . . that atrial fibrillation was likely to be recurrent . . . likely to cause illness or death . . . and long-term treatment for atrial fibrillation was warranted . . ..’’ In contrast, our study population consisted of a younger, healthier group of ED patients with a mean age of 61 years (54% younger than 65 years). Ninety-nine percent of patients in this investigation were categorized as having an atrial fibrillation episode of less than 48 hours’ duration. The AFFIRM investigators have acknowledged that their findings are not likely generalized to younger patients without risk of stroke, particularly those found to be in paroxysmal atrial fibrillation.

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Few studies have addressed the indications, efficacy, safety, and outcomes of electrical cardioversion for ED patients with recent-onset atrial fibrillation.1,15 Trends demonstrate that the frequency of atrial fibrillation– related hospital visits is increasing, suggesting a potential growing need to define the appropriate selection criteria for ED electrical cardioversion and the outcomes associated with this intervention.2 A recent publication addressed a comparable cohort of ED patients with recent-onset atrial fibrillation.1 In this investigation, Michael et al1 retrospectively evaluated 289 atrial fibrillation patients who underwent spontaneous, chemical, and electrical cardioversion in the ED. Eighty of these patients received attempted electrical cardioversion, with return to sinus rhythm in 71 (89%) patients. All patients who were successfully converted to sinus rhythm were discharged to home. These investigators concluded that most patients with recent-onset atrial fibrillation who undergo successful ED electrical cardioversion do not appear to require admission to the hospital and that immediate and short-term complications appear to be minor and relatively uncommon, findings similar to ours. In the study by Michael et al,1 approximately 83% of the electrical cardioversion patients had failed chemical cardioversion in the ED before the electrical cardioversion attempt. Similarly, we examined rates of cardioversion at one institution (Maine Medical Center, Portland, ME) during the study period for ED atrial fibrillation patients receiving rate control, chemical cardioversion, and electrical cardioversion. Seventeen percent of patients in each of the rate-control and chemical cardioversion groups converted to sinus rhythm during the ED encounter versus an electrical cardioversion success for 73% of patients in this institution and 86% for the multicenter cohort. Our limited findings and those of Michael et al suggest that the success and complication rate of electrical cardioversion may favor electrical cardioversion over pharmacologic cardioversion for the patient who is deemed eligible for ED rhythm conversion.27 A challenging area of ED atrial fibrillation investigation is the identification of variables associated with successful cardioversion and safe discharge from the hospital.28 Our data failed to disclose any demographic or clinical variable that was associated with successful electrical cardioversion. Future studies will need to address and derive a uniform approach to a defined ED atrial fibrillation population suitable for cardioversion or discharge. Rate-control interventions before the ED electrical cardioversion attempt did not appear to affect the likelihood of a successful conversion to sinus rhythm in this

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cohort. This finding is limited because of the potential biases and clinical factors affecting the treating emergency physician or ED consultant’s decision to use rate-control medications before electrical cardioversion. An attempt at chemical cardioversion before the ED electrical cardioversion procedure did not appear to affect the likelihood of electrical cardioversion success. Other authors have reported that a failed chemical cardioversion attempt or pretreatment with a pharmacologic cardioversion agent before electrical cardioversion may increase the likelihood of electrical cardioversion success.29,30 Spontaneous rhythm conversion rates of approximately 50% to 64% have been described for recent-onset atrial fibrillation patients with either no intervention or pulse rate control.31-33 These reports have primarily addressed inpatients with various durations of atrial fibrillation. Therefore, observation during 24 to 48 hours either as an inpatient or outpatient may represent an appropriate treatment strategy for selected patients. There are many components of any ED atrial fibrillation treatment pathway that affect patient outcomes, rhythm conversion success, and costs. Elements to be considered include the cost and efficacy of pharmacologic agents, the risk or benefit of anticoagulation and echocardiographic screening for thrombus, procedural sedation and analgesia agents, physician and health care provider use, patient disposition, and in the case of patients admitted to the hospital, the decision to utilize intensive care, cardiacmonitored, or nonmonitored environments. Each of these considerations is substantive and, in some cases, controversial, given the limited available literature and the spectrum of acute management options.11,34-36 Rendering comprehensive treatment in the ED for select patients with recent-onset atrial fibrillation would seem preferable to hospital admission. This strategy would appear to be advantageous for patients for whom the hospital management plan would be solely directed toward rhythm conversion and for whom an evaluation for atrial fibrillation etiology has been previously performed or deemed appropriate for outpatient workup. However, hospital admission and inpatient care will remain necessary when patients are deemed not to be candidates for ED electrical cardioversion, particularly when concomitant illness (eg, cardiac ischemia) or substantial thromboembolic risk factors are present at the patient encounter.4-12 Cardioversion in the ED setting by either chemical or electrical intervention is typically performed without patient anticoagulation during the procedure or the postprocedure period. Even with selection of patients at low relative risk for a thromboembolic

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event, this intervention may include a thromboembolic risk that exceeds any benefit gained by immediate rhythm cardioversion. The fundamental question of the benefit gained with recent-onset atrial fibrillation patient rhythm conversion remains a matter deserving further consideration. For the present, the identification of patients for whom rhythm conversion is appropriate will be based on a number of factors, including patient symptoms, exercise tolerance, comorbidities, previous atrial fibrillation episodes, and the preference of the patient and his or her physician.8,9,11 In this investigation, electrical cardioversion of selected patients with ED atrial fibrillation appeared effective and safe. This finding suggests the importance of including this intervention in more systematic future research. Author contributions: JHB conceived the study. JHB, DRV, TDS, and KD were participants in study design. All authors participated in and were responsible for data retrieval and record query. JHB was responsible for data management for the entire study. Abstract preparation was undertaken by JHB, DRV, KD, and TDS. HCT and JHB performed statistical review and management. JHB, HCT, and DRV were responsible for initial manuscript preparation, with all authors participating in final manuscript editing and submission for publication. JHB takes responsibility for the paper as a whole. Received for publication October 29, 2003. Revisions received January 29, 2004, and February 11, 2004. Accepted for publication February 12, 2004. Available online April 30, 2004. Presented at the Society for Academic Emergency Medicine annual meeting, Boston, MA, May 2003. The authors report this study did not receive any outside funding or support. Reprints not available from the authors. Address for correspondence: John H. Burton, MD, Department of Emergency Medicine, Maine Medical Center, 22 Bramhall Street, Portland, ME 04102; 207-842-7048, fax 207-842-7054; E-mail [email protected].

REFERENCES 1. Michael JA, Stiell IG, Agarwal S, et al. Cardioversion of paroxysmal atrial fibrillation in the emergency department. Ann Emerg Med. 1999;33:379-387. 2. Wattigney WA, Mensah GA, Croft JB. Increasing trends in hospitalization for atrial fibrillation in the United States, 1985 through 1999: implications for primary prevention. Circulation. 2003;108:711-716. 3. Feinberg WM, Blackshear JL, Laupacis A, et al. Prevalence, age distribution, and gender of patients with atrial fibrillation: analysis and implications. Arch Intern Med. 1995;155:469-473. 4. The National Heart, Lung, and Blood Institute Working Group on Atrial Fibrillation. Atrial fibrillation: current understandings and research imperatives. J Am Coll Cardiol. 1993;22:1830-1834. 5. Li H, Easley A, Barrington W, et al. Evaluation and management of atrial fibrillation in the emergency department. Emerg Med Clin North Am. 1998;16:389-403. 6. American Heart Association. Advanced Cardiac Life Support. Dallas, TX: American Heart Association; 1997:1-33.

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7. Anonymous. Proceedings of the American College of Chest Physicians 5th consensus on antithrombotic therapy. Chest. 1998;114:439S-769S. 8. Fuster V, Ryden LE, Asinger RW, et al. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation: executive summary. J Am Coll Cardiol. 2001;38:1266-1334. 9. de Latorre F, Nolan J, Robertson C, et al. European Resuscitation Council Guidelines 2000 for adult advanced life support. Resuscitation. 2001;48:211-221. 10. Koenig BO, Ross MA, Jackson RE. An emergency department observation unit protocol for acute-onset atrial fibrillation is feasible. Ann Emerg Med. 2002;39:374-381. 11. Snow V, Weiss KB, LeFevre M, et al. Management of newly detected atrial fibrillation: a practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Intern Med. 2003;139:1009-1017. 12. Weigner MJ, Caulfield TA, Danias PG, et al. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med. 1997;126:615-620. 13. Gentile F, Elhendy A, Khandheria BK, et al. Safety of electrical cardioversion in patients with atrial fibrillation. Mayo Clin Proc. 2002;77:897-904. 14. Jung F, DiMarco JP. Treatment strategies for atrial fibrillation. Am J Med. 1998;104: 272-286. 15. Domanovits H, Schillinger M, Thoennissen J, et al. Termination of recent-onset atrial fibrillation/flutter in the emergency department: a sequential approach with intravenous ibutilide and external electrical cardioversion. Resuscitation. 2000;45: 181-187. 16. Page RL, Kerber RE, Russell JK, et al. Biphasic versus monophasic shock waveform for conversion of atrial fibrillation: the results of an international randomized, double-blind multicenter trial. J Am Coll Cardiol. 2002;39:1956-1963. 17. Berger M, Schweitzer P. Timing of thromboembolic events after electrical cardioversion of atrial fibrillation or flutter: a retrospective analysis. Am J Cardiol. 1998; 82:1545-1547, A8. 18. Manning WJ, Silverman DI, Katz SE, et al. Temporal dependence of the return of atrial mechanical function on the mode of cardioversion of atrial fibrillation to sinus rhythm. Am J Cardiol. 1995;75:624-626. 19. Grimm RA, Leung DY, Black IW, et al. Left atrial appendage ‘‘stunning’’ after spontaneous conversion of atrial fibrillation demonstrated by transesophageal Doppler echocardiography. Am Heart J. 1995;130:174-176. 20. Bellotti P, Spirito P, Lupi G, et al. Left atrial appendage function assessed by transesophageal echocardiography before and on the day after elective cardioversion for nonvalvular atrial fibrillation. Am J Cardiol. 1998;81:1199-1202. 21. Harjai K, Mobarek S, Abi-Samra F, et al. Mechanical dysfunction of the left atrium and the left atrial appendage following cardioversion of atrial fibrillation and its relation to total electrical energy used for cardioversion. Am J Cardiol. 1998;81: 1125-1129. 22. Antonielli E, Pizzuti A, Bassignana A, et al. Transesophageal echocardiographic evidence of more pronounced left atrial stunning after chemical (propafenone) rather than electrical attempts at cardioversion from atrial fibrillation. Am J Cardiol. 1999;84: 1092-1100. 23. Falcone RA, Morady F, Armstrong WF. Transesophageal echocardiographic evaluation of left atrial appendage function and spontaneous contrast formation after chemical or electrical cardioversion of atrial fibrillation. Am J Cardiol. 1996;78:435-439. 24. Klein AL, Grimm RA, Murray RD, et al. Use of transesophageal echocardiography to guide cardioversion in patients with atrial fibrillation. N Engl J Med. 2001;344:1411-1420. 25. Mead GE, Flapan AD, Elder AT. Electrical cardioversion for atrial fibrillation and flutter. Cochrane Database Sys Rev. 2002;1:CD002903. 26. Wyse DG, Waldo AL, DiMarco JP, et al. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med. 2002;347:1825-1833. 27. Fresco C, Proclemer A. Clinical challenge, II: management of recent onset atrial fibrillation: PAFIT-2 Investigators. Eur Heart J. 1996;17(Suppl C):41-47. 28. Mulcahy B, Coates WC, Henneman PL, et al. New-onset atrial fibrillation: when is admission medically justified. Acad Emerg Med. 1996;3:114-119. 29. Marcus GM, Sung RJ. Antiarrythmic agents in facilitating electrical cardioversion of atrial fibrillation and promoting maintenance of sinus rhythm. Cardiology. 2001;95:1-8. 30. Oral H, Souza J, Michaud GF, et al. Facilitating transthoracic cardioversion of atrial fibrillation with ibutilide pretreatment. N Engl J Med. 1999;340:1849-1854. 31. Cotter G, Blatt A, Kaluski E, et al. Conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm: the effect of no treatment and high-dose amiodarone: a randomized, placebo-controlled study. Eur Heart J. 1999;20:1833-1842. 32. Danias PG, Caulfield TA, Weigner MJ, et al. Likelihood of spontaneous conversion of atrial fibrillation to sinus rhythm. J Am Coll Cardiol. 1998;31:588-592. 33. Dell’Orfano JT, Patel H, Wolbrette DL, et al. Acute treatment of atrial fibrillation: spontaneous conversion rates and cost of care. Am J Cardiol. 1999;83:788-790. 34. Naccarelli GV, Dell’Orfano JT, Wolbrette DL, et al. Cost-effective management of acute atrial fibrillation: role of rate control, spontaneous conversion, medical and direct

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current cardioversion, transesophageal echocardiography, and antiembolic therapy. Am J Cardiol. 2000;85:36D-45D. 35. Wang TJ, Massaro JM, Levy D, et al. A risk score for predicting stroke or death in individuals with new-onset atrial fibrillation in the community. JAMA. 2003;290: 1049-1056. 36. Zarkin GA, Bala MV, Calingaert B, et al. The cost-effectiveness of ibutilide versus electrical cardioversion in the conversion of atrial fibrillation and flutter to normal rhythm. Am J Managed Care. 1997;3:1387-1394.

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