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Background For patients with atrial fibrillation seen in the emergency department (ED) following a transient ischemic attack (TIA) or minor stroke, the impact of initiating oral anticoagulation immediately rather than deferring the decision to outpatient follow-up is unknown. Methods and Results We conducted a planned secondary data analysis of a prospective cohort of 11 507 adults in 13 Canadian EDs between 2006 and 2018. Patients were eligible if they were aged 18 years or older, with a final diagnosis of TIA or minor stroke with previously documented or newly diagnosed atrial fibrillation. The primary outcome was subsequent stroke, recurrent TIA, or all-cause mortality within 90 days of the index TIA diagnosis. Secondary outcomes included stroke, recurrent TIA, or death and rates of major bleeding. Of 11 507 subjects with TIA/minor stroke, atrial fibrillation was identified in 11.2% (1286, mean age, 77.3 [SD 11.1] years, 52.4% male). Over half (699; 54.4%) were already taking anticoagulation, 89 (6.9%) were newly prescribed anticoagulation in the ED. By 90 days, 4.0% of the atrial fibrillation cohort had experienced a subsequent stroke, 6.5% subsequent TIA, and 2.6% died. Results of a multivariable logistic regression indicate no association between prescribed anticoagulation in the ED and these 90-day outcomes (composite odds ratio, 1.37 [95% CI, 0.74-2.52]). Major bleeding was found in 5 patients, none of whom were in the ED-initiated anticoagulation group. Conclusions Initiating oral anticoagulation in the ED following new TIA was not associated with lower recurrence rates of neurovascular events or all-cause mortality in patients with atrial fibrillation.

Background: We sought to evaluate safety of electrical cardioversion (ECV) for patients with acute atrial fibrillation (AF) or atrial flutter (AFL) in the emergency department (ED)., Methods: This was an analysis of data from 4 multicentre AF/AFL studies conducted from 2008 to 2019 at 23 large EDs. We included adult patients who received attempts at ECV and who had presented acutely after symptom onset. Staff manually reviewed study and clinical records to abstract data., Results: We evaluated 1736 ECV cases with a mean age of 60.1 years and 67.1% male. The overall success of ECV was 90.2% (95% confidence interval 88.7%-91.6%), with 4.9% of patients admitted. ED physicians performed the ECV in 95.2% and provided sedation in 96.5%; 13.9% (12.3%-15.7%) of cases experienced important adverse events that required treatment, and 0.4% were classified as life threatening. Another 5.6% had adverse events that did not require treatment. Logistic regression found that the RAFF-3 study cohort (odds ratio [OR] 2.0), age ≥ 85 years (OR 2.1), coronary artery disease (OR 1.5), midazolam (OR 1.9), and fentanyl (OR 1.5) were associated with important adverse events., Conclusions: This large evaluation of the safety of ECV for acute AF/AFL in the ED found that while serious adverse events were rare, there were a concerning number of events following sedation that required intervention. Physicians should be aware that older age, coronary artery disease, and fentanyl are associated with higher risks of important adverse events. This study provides more information for shared decision making discussions with patients when choosing between drug-shock and shock-only cardioversion strategies., (Copyright © 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: We sought to improve care of patients with acute atrial fibrillation (AF) and flutter (AFL) in the emergency department (ED) by implementing the Canadian Association of Emergency Physicians (CAEP) Acute AF/AFL Best Practices Checklist., Methods: We conducted a stepped-wedge cluster randomised trial at 11 large community and academic hospital EDs in 5 Canadian provinces and enrolled consecutive AF/AFL patients. The study intervention was introduction of the CAEP Checklist with the use of a knowledge translation-implementation approach that included behaviour change techniques and organisation/system-level strategies. The primary outcome was length of stay in ED, and secondary outcomes were discharge home, use of rhythm control, adverse events, and 30-day status. Analysis used mixed-effects regression adjusting for covariates., Results: Patient visits in the control (n = 314) and intervention (n = 404) periods were similar with mean age 62.9 years, 54% male, 71% onset < 12 hours, and 86% AF, 14% AFL. We observed a reduction in length of stay of 20.9% (95% confidence interval [CI] 5.5%-33.8%; P = 0.01), an increase in use of rhythm control (adjusted odds ratio [OR] 4.5, 95% CI 1.8-11.6; P = 0.002), and a decrease in use of rate-control medications (OR 0.5, 95% CI 0.2-0.9; P = 0.02). There was no change in adverse events and no strokes or deaths by 30 days., Conclusions: The RAFF-3 trial led to optimised care of AF/AFL patients with decreased ED lengths of stay, increased ED rhythm control by drug or electricity, and no increase in adverse events. Early cardioversion allows AF/AFL patients to quickly resume normal activities., (Copyright © 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: Recent studies have presented concerning data on the safety of cardioversion for acute atrial fibrillation and flutter. We conducted this meta-analysis to evaluate the effect of oral anticoagulation use on thromboembolic events post-cardioversion of low-risk acute atrial fibrillation and flutter patients of < 48 h in duration., Methods: We searched MEDLINE, Embase, and Cochrane from inception through February 6, 2020 for studies reporting thromboembolic events post-cardioversion of acute atrial fibrillation and flutter. Main outcome was thromboembolic events within 30 days post-cardioversion. Primary analysis compared thromboembolic events based on oral anticoagulation use versus no oral anticoagulation use. Secondary analysis was based on baseline thromboembolic risk. We performed meta-analyses where 2 or more studies were available, by applying the DerSimonian-Laird random-effects model. Risk of bias was assessed with the Quality in Prognostic Studies tool., Results: Of 717 titles screened, 20 studies met inclusion criteria. Primary analysis of seven studies with low risk of bias demonstrated insufficient evidence regarding the risk of thromboembolic events associated with oral anticoagulation use (RR = 0.82 where RR < 1 suggests decreased risk with oral anticoagulation use; 95% CI 0.27 to 2.47; I 2  = 0%). Secondary analysis of 13 studies revealed increased risk of thromboembolic events with high baseline thromboembolic risk (RR = 2.25 where RR > 1 indicates increased risk with higher CHADS 2 or CHA 2 DS 2 -VASc scores; 95% CI 1.25 to 4.04; I 2  = 0%)., Conclusion: Primary analysis revealed insufficient evidence regarding the effect of oral anticoagulation use on thromboembolic events post-cardioversion of low-risk acute atrial fibrillation and flutter, though the event rate is low in contemporary practice. Our findings can better inform patient-centered decision-making when considering 4-week oral anticoagulation use for acute atrial fibrillation and flutter patients.

Background: Acute atrial flutter has one-tenth the prevalence of acute atrial fibrillation in the emergency department (ED) but shares many management strategies. Our aim was to compare conversion from acute atrial flutter to sinus rhythm between pharmacological cardioversion followed by electrical cardioversion (Drug-Shock), and electrical cardioversion alone (Shock-Only)., Methods: We conducted a randomized, blinded, placebo-controlled comparison of attempted pharmacological cardioversion with IV procainamide followed by electrical cardioversion if necessary, and placebo infusion followed by electrical cardioversion. We enrolled stable patients with a primary diagnosis of acute acute atrial flutter at 11 academic EDs. The primary outcome was conversion to normal sinus rhythm., Findings: From July 2013 to October 2018, we enrolled 76 patients, and none were lost to follow-up. Comparing the Drug-Shock to the Shock-Only group, conversion to sinus rhythm occurred in 33 (100%) versus 40 (93%) (absolute difference 7.0%; 95% CI - 0.6 to 14.6; P = 0.25). Median time to conversion from start of infusion in the Drug-Shock group was 24 min (IQR 21-82) but only 9 (27%) cases were converted with IV procainamide. Patients in both groups had similar outcomes at 14 days; there were no strokes or deaths., Interpretation: This trial found that the Drug-Shock strategy is potentially superior but that either approach to immediate rhythm control in the ED for patients with acute acute atrial flutter is highly effective, rapid, and safe in restoring sinus rhythm and allowing patients to go home and return to normal activities. Unlike the case of atrial fibrillation, we found that IV procainamide alone was infrequently effective.

Background: Acute atrial fibrillation is the most common arrythmia treated in the emergency department. Our primary aim was to compare conversion to sinus rhythm between pharmacological cardioversion followed by electrical cardioversion (drug-shock), and electrical cardioversion alone (shock-only). Our secondary aim was to compare the effectiveness of two pad positions for electrical cardioversion., Methods: We did a partial factorial trial of two protocols for patients with acute atrial fibrillation at 11 academic hospital emergency departments in Canada. We enrolled adult patients with acute atrial fibrillation. Protocol 1 was a randomised, blinded, placebo-controlled comparison of attempted pharmacological cardioversion with intravenous procainamide (15 mg/kg over 30 min) followed by electrical cardioversion if necessary (up to three shocks, each of ≥200 J), and placebo infusion followed by electrical cardioversion. For patients having electrical cardioversion, we used Protocol 2, a randomised, open-label, nested comparison of anteroposterior versus anterolateral pad positions. Patients were randomly assigned (1:1, stratified by study site) for Protocol 1 by on-site research personnel using an online electronic data capture system. Randomisation for Protocol 2 occurred 30 min after drug infusion for patients who had not converted and was stratified by site and Protocol 1 allocation. Patients and all research and emergency department staff were masked to treatment allocation for Protocol 1. The primary outcome was conversion to normal sinus rhythm for at least 30 min at any time after randomisation and up to a point immediately after three shocks. Protocol 1 was analysed by intention to treat and Protocol 2 excluded patients who did not receive electrical cardioversion. This study is registered at ClinicalTrials.gov, number NCT01891058., Findings: Between July 18, 2013, and Oct 17, 2018, we enrolled 396 patients, and none were lost to follow-up. In the drug-shock group (n=204), conversion to sinus rhythm occurred in 196 (96%) patients and in the shock-only group (n=192), conversion occurred in 176 (92%) patients (absolute difference 4%; 95% CI 0-9; p=0·07). The proportion of patients discharged home was 97% (n=198) versus 95% (n=183; p=0·60). 106 (52%) patients in the drug-shock group converted after drug infusion only. No patients had serious adverse events in follow-up. The different pad positions in Protocol 2 (n=244), had similar conversions to sinus rhythm (119 [94%] of 127 in anterolateral group vs 108 [92%] of 117 in anteroposterior group; p=0·68)., Interpretation: Both the drug-shock and shock-only strategies were highly effective, rapid, and safe in restoring sinus rhythm for patients in the emergency department with acute atrial fibrillation, avoiding the need for return to hospital. The drug infusion worked for about half of patients and avoided the resource intensive procedural sedation required for electrical cardioversion. We also found no significant difference between the anterolateral and anteroposterior pad positions for electrical cardioversion. Immediate rhythm control for patients in the emergency department with acute atrial fibrillation leads to excellent outcomes., Funding: Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objectives: Although procedural sedation for cardioversion is a common event in emergency departments (EDs), there is limited evidence surrounding medication choices. We sought to evaluate geographic and temporal variation in sedative choice at multiple Canadian sites, and to estimate the risk of adverse events due to sedative choice., Methods: This is a secondary analysis of one health records review, the Recent Onset Atrial Fibrillation or Flutter-0 (RAFF-0 [n=420, 2008]) and one prospective cohort study, the Recent Onset Atrial Fibrillation or Flutter-1 (RAFF-1 [n=565, 2010 - 2012]) at eight and six Canadian EDs, respectively. Sedative choices within and among EDs were quantified, and the risk of adverse events was examined with adjusted and unadjusted comparisons of sedative regimes., Results: In RAFF-0 and RAFF-1, the combination of propofol and fentanyl was most popular (63.8% and 52.7%) followed by propofol alone (27.9% and 37.3%). There were substantially more adverse events in the RAFF-0 data set (13.5%) versus RAFF-1 (3.3%). In both data sets, the combination of propofol/fentanyl was not associated with increased adverse event risk compared to propofol alone., Conclusion: There is marked variability in procedural sedation medication choice for a direct current cardioversion in Canadian EDs, with increased use of propofol alone as a sedation agent over time. The risk of adverse events from procedural sedation during cardioversion is low but not insignificant. We did not identify an increased risk of adverse events with the addition of fentanyl as an adjunctive analgesic to propofol.

Study Objective: Recent-onset atrial fibrillation and flutter are the most common arrhythmias managed in the emergency department (ED). We evaluate the management and 30-day outcomes for recent-onset atrial fibrillation and flutter patients in Canadian EDs, where cardioversion is commonly practiced., Methods: We conducted a prospective cohort study in 6 academic hospital EDs and enrolled patients who had atrial fibrillation and flutter onset within 48 hours. Patients were followed for 30 days by health records review and telephone. Adverse events included death, stroke, acute coronary syndrome, heart failure, subsequent admission, or ED electrocardioversion., Results: We enrolled 1,091 patients with mean age 63.9 years, atrial fibrillation 84.7%, atrial flutter 15.3%, hospital admission 9.0%, and converted to sinus rhythm 80.1%. Although 10.5% of recent-onset atrial fibrillation and flutter patients had adverse events within 30 days, there were no related deaths and 1 stroke (0.1%). Adjusted odds ratios for factors associated with adverse event were hours from onset (1.03/hour; 95% confidence interval [CI] 1.01 to 1.05), history of stroke or transient ischemic attack (2.09; 95% CI 1.01 to 4.36), and pulmonary congestion on chest radiograph (7.37; 95% CI 2.40 to 22.64). Patients who left the ED in sinus rhythm were much less likely to experience an adverse event (P<.001)., Conclusion: Although most recent-onset atrial fibrillation and flutter patients were treated aggressively in the ED, there were few 30-day serious outcomes. Physicians underprescribed oral anticoagulants. Potential risk factors for adverse events include longer duration from arrhythmia onset, previous stroke or transient ischemic attack, pulmonary congestion on chest radiograph, and not being in sinus rhythm at discharge. An ED strategy of sinus rhythm restoration and discharge in most patients is effective and safe., (Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.)

Objective: A cardiac source is often implicated in strokes where the deficit includes aphasia. However, less is known about the etiology of isolated aphasia during transient ischemic attack (TIA). Our objective was to determine whether patients with isolated aphasia are likely to have a cardioembolic etiology for their TIA., Methods: We prospectively studied a cohort of TIA patients in eight tertiary-care emergency departments. Patients with isolated aphasia were identified by the treating physician at the time of emergency department presentation. Patients with dysarthria (i.e., a phonation disturbance) were not included. Potential cardiac sources for embolism were defined as atrial fibrillation on history, electrocardiogram, Holter monitor, atrial fibrillation on echocardiography, or thrombus on echocardiography., Results: Of the 2,360 TIA patients identified, 1,155 had neurological deficits at the time of the emergency physician assessment and were included in this analysis, and 41 had isolated aphasia as their only neurological deficit. Patients with isolated aphasia were older (73.9±10.0 v. 67.2±14.5 years; p=0.003), more likely to have a history of heart failure (9.8% v. 2.6%; p=0.027), and were twice as likely to have any cardiac source of embolism (22.0% v. 10.6%; p=0.037)., Conclusions: Isolated aphasia is associated with a high rate of cardioembolic sources of embolism after TIA. Emergency patients with isolated aphasia diagnosed with a TIA warrant a rapid and thorough assessment for a cardioembolic source.

Objective: To derive a simple clinical prediction rule identifying patients at high risk of developing new-onset postoperative atrial fibrillation (POAF) after cardiac surgery., Design: Retrospective analysis on prospectively collected observational data., Setting: A university-affiliated cardiac hospital., Participants: Adult patients undergoing coronary artery bypass grafting and/or valve surgery., Interventions: Observation for the occurrence of new-onset postoperative atrial fibrillation., Measurements and Main Results: Details on 28 preoperative variables from 999 patients were collected and significant predictors (p<0.2) were inserted into multivariable logistic regression and reconfirmed with recursive partitioning. A total of 305 (30.5%) patients developed new-onset POAF. Eleven variables were associated significantly with atrial fibrillation. A multivariable logistic regression model included left atrial dilatation, mitral valve disease, and age. Coefficients from the model were converted into a simple 7-point predictive score. The risk of POAF per score is: 15.0%, if 0; 20%, if 1; 27%, if 2; 35%, if 3; 44%, if 4; 53%, if 5; 62%, if 6; and 70%, if 7. A score of 4 has a sensitivity of 44% and a specificity of 82% for POAF. A score of 6 has a sensitivity of 11% and a specificity of 97%. Bootstrapping with 5,000 samples confirmed the final model provided consistent predictions., Conclusions: This study proposed a simple predictive score incorporating three risk variables to identify cardiac surgical patients at high risk of developing new-onset POAF. Preventive treatment should target patients ≥ 65 years with left atrial dilatation and mitral valve disease., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: It is believed that when patients present to the emergency department (ED) with recent-onset atrial fibrillation or flutter (RAFF), controlling the ventricular rate before cardioversion improves the success rate. We evaluated the influence of rate control medication and other variables on the success of cardioversion., Methods: This secondary analysis of a medical records review comprised 1,068 patients with RAFF who presented to eight Canadian EDs over 12 months. Univariate analysis was performed to find associations between predictors of conversion to sinus rhythm including use of rate control, rhythm control, and other variables. Predictive variables were incorporated into the multivariate model to calculate adjusted odds ratios (ORs) associated with successful cardioversion., Results: A total of 634 patients underwent attempted cardioversion: 428 electrical, 354 chemical, and 148 both. Adjusted ORs for factors associated with successful electrical cardioversion were use of rate control medication, 0.39 (95% confidence interval [CI] 0.21-0.74); rhythm control medication, 0.28 (95% CI 0.15-0.53); and CHADS₂ score > 0, 0.43 (95% CI 0.15-0.83). ORs for factors associated with successful chemical cardioversion were use of rate control medication, 1.29 (95% CI 0.82-2.03); female sex, 2.37 (95% CI 1.50-3.72); and use of procainamide, 2.32 (95% CI 1.43-3.74)., Conclusion: We demonstrated reduced successful electrical cardioversion of RAFF when patients were pretreated with either rate or rhythm control medication. Although rate control medication was not associated with increased success of chemical cardioversion, use of procainamide was. Slowing the ventricular rate prior to cardioversion should be avoided.

Study Objective: Although recent-onset atrial fibrillation and flutter are common arrhythmias managed in the emergency department (ED), there is insufficient evidence to help physicians choose between 2 competing treatment strategies, rate control and rhythm control. We seek to evaluate variation in ED management practices for recent-onset atrial fibrillation and flutter patients at multiple Canadian sites and to determine whether hospital site was an independent predictor of attempted cardioversion., Methods: We conducted a cross-sectional survey by health records review on an observational cohort of all eligible adult recent-onset atrial fibrillation and flutter cases, with onset of symptoms less than 48 hours, treated at 8 academic hospital EDs during a 12-month period, and evaluated the variation in practice among sites for important management strategies., Results: Among the 1,068 study patients, 88.3% had atrial fibrillation and 11.7% had atrial flutter. The proportion of cases managed with rhythm control was 59.4% (interhospital range 42% to 85%) and, among these, electrocardioversion was attempted first for 44.2% (range 7% to 69%). There was variation in most management strategies, including use of rate control drugs 54.9% (range 37% to 65%), choice of procainamide as rhythm control drug 62.1% (range 15% to 89%), referral to cardiology in the ED 30.7% (range 16% to 64%), use of heparin 13.7% (range 1% to 29%), and outpatient cardiology referral 43.0% (range 30% to 65%). Adverse events were relatively uncommon and transient for patients undergoing attempts at pharmacologic (13.0%) or electrocardioversion (12.1%). Overall, 83.3% of patients were discharged home from the ED (range 73% to 90%). After controlling for 12 covariates, multivariate logistic regression found that factors independently associated with attempted cardioversion were age (odds ratio [OR] 0.97; 95% confidence interval [CI] 0.95 to 0.98), history of electrocardioversion (OR 2.73; 95% CI 1.56 to 4.80), associated heart failure (OR 0.29; 95% CI 0.09 to 0.95), and hospital site (ORs ranged from 0.38 to 3.05)., Conclusion: We demonstrated a high degree of variation in management approaches for recent-onset atrial fibrillation and flutter patients treated in academic hospital EDs. Individual hospital site, age, previous cardioversion, and associated heart failure were independent predictors for the use of rhythm control., (Copyright © 2010 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.)

Objectives: Vernakalant is a relatively atrial-selective antiarrhythmic agent that has been shown to successfully convert atrial fibrillation (AF) to normal sinus rhythm for some patients whose onset of dysrhythmia occurred less than 7 days previously. This study sought to evaluate the efficacy and safety of vernakalant for patients with recent-onset AF., Methods: This was a post hoc analysis of patients with recent-onset AF (> 3 to ≤ 48 hours) enrolled in the double-blind, placebo-controlled Atrial arrhythmia Conversion Trial (ACT) I and the open-label ACT IV trials. The studies enrolled adults presenting with AF to 78 emergency departments (ED) and cardiac clinics in six countries. Patients received a 10-minute intravenous infusion of vernakalant or placebo, followed by an additional infusion if necessary. Efficacy assessments included conversion to sinus rhythm within 90 minutes and median time to conversion. Safety evaluations included telemetry, Holter monitoring, and adverse events (AEs)., Results: Of the 290 patients, 229 received vernakalant, 61 received placebo, and the overall mean age was 59 years. The vernakalant and placebo groups were similar. Of all patients given vernakalant, 136 (59.4%) converted to sinus rhythm within 90 minutes, compared with three (4.9%) placebo patients. The median time to conversion with vernakalant was 12 minutes (interquartile range = 7-24.5 minutes). Clinically significant bradycardia and hypotension were uncommon, and no cases of torsade de pointes or ventricular fibrillation occurred., Conclusions: Vernakalant rapidly converted recent-onset AF to sinus rhythm in over half of patients, was well tolerated, and has the potential to offer an important therapeutic option for rhythm control of recent-onset AF in the ED., (© 2010 by the Society for Academic Emergency Medicine.)

Objective: There is no consensus on the optimal management of recent-onset episodes of atrial fibrillation or flutter. The approach to these conditions is particularly relevant in the current era of emergency department (ED) overcrowding. We sought to examine the effectiveness and safety of the Ottawa Aggressive Protocol to perform rapid cardioversion and discharge patients with these arrhythmias., Methods: This cohort study enrolled consecutive patient visits to an adult university hospital ED for recent-onset atrial fibrillation or flutter managed with the Ottawa Aggressive Protocol. The protocol includes intravenous chemical cardioversion, electrical cardioversion if necessary and discharge home from the ED., Results: A total of 660 patient visits were included, 95.2% involving atrial fibrillation and 4.9% involving atrial flutter. The mean age of patients enrolled was 64.5 years. In total, 96.8% were discharged home and, of those, 93.3% were in sinus rhythm. All patients were initially administered intravenous procainamide, with a 58.3% conversion rate. A total of 243 patients underwent subsequent electrical cardioversion with a 91.7% success rate. Adverse events occurred in 7.6% of cases: hypotension 6.7%, bradycardia 0.3% and 7-day relapse 8.6%. There were no cases of torsades de pointes, stroke or death. The median lengths of stay in the ED were as follows: 4.9 hours overall, 3.9 hours for those undergoing conversion with procainamide and 6.5 hours for those requiring electrical conversion., Conclusion: This is the largest study to date to evaluate the Ottawa Aggressive Protocol, a unique approach to cardioversion for ED patients with recent-onset episodes of atrial fibrillation and flutter. Our data demonstrate that the Ottawa Aggressive Protocol is effective, safe and rapid, and has the potential to significantly reduce hospital admissions and expedite ED care.

Objectives: Acute atrial fibrillation and flutter are very common arrhythmias seen in emergency department (ED) patients, but there is no consensus for their optimal management. The objective of this study was to examine the efficacy and safety of intravenous (IV) procainamide for acute atrial fibrillation or flutter., Methods: This health records review included a consecutive cohort of ED patients with acute-onset atrial fibrillation or atrial flutter who received IV procainamide at one university hospital ED during a five-year period. The standard clinical protocol involved IV infusion of 1 g of procainamide over 60 minutes, followed by electrical cardioversion if necessary. A trained observer extracted data from the original clinical records. Outcome measurements included conversion to sinus rhythm, adverse events, and relapse up to seven days., Results: The 341 study patients had a mean age of 63.9 years (SD +/- 15.5 years), and 56.6% were male. The conversion rates were 52.2% (95% confidence interval = 47% to 58%) for 316 atrial fibrillation cases and 28.0% (95% confidence interval = 13% to 46%) for 25 atrial flutter cases. Mean dose given was 860.7 mg (SD +/- 231.2 mg), and median time to conversion was 55 minutes. Adverse events occurred in 34 cases (10.0%): hypotension, 8.5%; bradycardia, 0.6%; atrioventricular block, 0.6%; and ventricular tachycardia, 0.3%. There were no cases of torsades de pointes, cerebrovascular accident, or death. Most patients (94.4%) were discharged home, but 2.9% of patients returned with a recurrence of atrial fibrillation within seven days., Conclusions: This study of acute atrial fibrillation or flutter patients treated in the ED with IV procainamide suggests that this treatment is safe and effective in this setting. Procainamide should be prospectively compared with other ED strategies.