EBQ:48hr Cardioversion for Afib

Complete Journal Club Article
Weigner MJ 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(8):615-620.
PubMed Full text PDF

Clinical Question

For patients presenting with Atrial Fibrillation lasting less than 48 hours, what is the incidence of cardioversion-related thromboembolism?


Major Points

  • Cardioversion of atrial fibrillation is necessary to improve cardiac function, relieve symptoms and decrease the rate of thrombus formation.[1]. With many patients presenting acutely for new onset atrial fibrillation within 48hrs, this study assessed the risk of thromboembolic event following cardioversion or spontaneous conversion after rate control. Of the 357 patients converted to sinus rhythm within the first 48hrs only 3 patients (0.8%) experienced a thromboembolic event.
  • An additional review of 5 studies on the safety of ED cardioversion suggest that the major complication occurring from ED cardioversion relates to the procedural sedation with rare complications from the cardioversion event.[2]

Study Design

  • Prospective cohort study
  • Two Centers:
    • Beth Israel Deaconess Hospital - Boston, Massachusetts (Jan. 1, 1990 - Sept. 25, 1995)
    • Univ. Connecticut Health Center - Farmington, Connecticut (Sept. 28, 1991 - April 29, 1996)
  • N=375
  • Primary Outcome: incidence of cardioversion related clinical thromboembolism


Patient Demographics

  • 214 Women, 161 Men
  • Mean age: 68 years
  • Predisposing factors to Atrial Fib:
    • Hypertension: 41.7%
    • Active Infection: 6.7%
    • Alcohol Intake: 5.9%
  • Rheumatic Heart Disease: 1.9%
  • Other 1.9
  • Comorbidities:
    • Prio A. Fib: 48.3%
    • CAD: 30.4%
    • No underlying disorders: 24.3%
    • MI: 10.4%
    • Prior Thromboembolism: 6.1%

Inclusion Criteria

  • Atrial Fibrillation < 48hrs
    • onset estimated on basis of: palpitations, dyspnea, angina, & dizziness

Exclusion Criteria

  • Inability to identify duration of atrial fibrillation
  • Atrial Fibrillation > 48hrs
  • Presentation witih an acute thromboembolism
  • On long term warfarin with INR >1.6



Primary Outcome

  • 3 total ischemic CVA
  • All patients were > 80yrs old and had spontaneous cardioversion after rate control.
  • CVA occured after spontaneous cardioversion in all cases

Secondary Outcomes

  • Conversion rates to sinus rhythm:
    • 95.2% total conversion
    • 66.7% spontaneous conversion
    • 28.5% active cardioversion

Subgroup analysis

  • On prior anticoagulation or antiplatelet: 24.8%
  • On warfarin and subtherapeautic (INR<1.6): 3.2%
  • On rate-control medication: 21.3%
  • On antiarhythmic: 13.1%
  • Mean duration of atrial fibriliation prior to cardioversion: 1.7 days
  • Thromboembolism on Anticoagulation vs. No Anticoagulation (including aspirin)
0.8% vs 0.9% (p >0.2)
  • Thromboembolism on Anticoagulation(including asprin) vs. No Anticoagulation
1.3% vs 0.5% (p>0.2)

Criticisms & Further Discussion

  • This study was not an ED population however patients were of a similar population as most ED patients.
  • No clear conclusions can be drawn from the subgroup analysis regarding need for anticoagulation prior to cardioversion.
  • The ACCP, recommend against acute anticoagulation for high risk patients getting cardioversion (Grade 2C)[3]

Additional Resources

ERCast Podcast-Cardioversion




  1. Pritchett E et al. Management of atrial fibrillation. NEJM. 1992;326:1264-71
  2. von Besser K. et al. Is discharge to home after emergency department cardioversion safe for the treatment of recent-onset atrial fibrillation? Ann Emerg Med. 2011 Dec;58(6):517-20
  3. Singer D. et al. Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest. 2004 Sep;126(3 Suppl):429S-456S