KT Evidence Bite: Cardioversion and Thromboembolism

In Knowledge Translation by Eve PurdyLeave a Comment

Editor’s note: This is a series based on work done by three physicians (Patrick ArchambaultTim Chaplin, and our BoringEM Managing editor Teresa Chan)  for the Canadian National Review Course (NRC). You can read a description of this course here.

The NRC brings EM residents from across the Canada together in their final year for a crash course on everything emergency medicine. Since we are a specialty with heavy allegiance to the tenets of Evidence-Based Medicine, we thought we would serially release the biggest, baddest papers in EM to help the PGY5s in their studying via a spaced-repetition technique. And, since we’re giving this to them, we figured we might as well share those appraisals with the #FOAMed community! We have kept much of the material as drop downs so that you can quiz yourself on the studies.

Paper: The FinCV (Finnish CardioVersion) study of cardioversion of acute atrial fibrillation


Airaksinen KE, GronbergT, NuotioI, et al. The FinCV (Finnish CardioVersion) study. J Am Coll Cardiol. 2013;62(13):1187-1192. PMID: 23850908

Summarized by: Tim Chaplin
Reviewed by: Teresa Chan & Patrick Archambault


Clinical Question

What is the incidence of and risk factors for thromboembolic events after ED cardioversion of acute atrial fibrillation?

Population Adult patients with primary diagnosis of atrial fibrillation who were successfully cardioverted in the ED within 48hrs of atrial fibrillation onset. Atrial fibrillation of cardiac cause.
Comparison factors (observational study)Large number of clinical characteristics including: age, gender, hypertension, heart failure, diabetes, other comorbidities, medications, time to cardioversion, method of cardioversion etc.
OutcomeThromboembolic events (clinically stroke or systemic embolism confirmed by CT or MRI, surgery, or autopsy) within 30 days after cardioversion.


This was a retrospective database analysis of adult (>18yo) patients who presented to 3 large EDs in Finland with a primary diagnosis of acute (<48hrs) atrial fibrillation and who were cardioverted successfully in the ED. These patients did not receive peri-procedural anticoagulation. Baseline characteristics were recorded. A univariate analysis followed by multivariable logistic regression was performed to identify risk factors. 


n= 2481 patients with a total of 5116 successful cardioversions (patients were included multiple times if multiple successful cardioversion occurred within study period) of which 88% were electrical cardioversions.

  • Overall incidence for thromboembolism was 0.7% with events occurring at an average of 2 days post cardioversion

Risk factors for thromboembolism

  • cardioversion > 12 hrs after onset of atrial fibrillation (1.1%) vs <12 hrs after onset( 0.3%)
  • Multivariable regression identified independent factors:
    • >12 hrs from symptom onset
    • advancing age
    • female sex
    • heart failure
    • diabetes


Early cardioversion (<12hrs) is associated with lower thromboembolic events. High risk patients should be considered for peri-procedural and long-term anticoagulation. This is in accordance with the 2010 Europena guidelines.


Take Home Point

1. Earlier cardioversion (<12hrs) may be safer than later (12hrs) cardioversion for patients who present with acute onset atrial fibrillation.

2. Peri-procedural anticoagulation (i.e. with IV heparin) may reduce the risk of thromboembolic events in high risk patients undergoing ED cardioversion of acute atrial fibrillation


EBM Considerations

  • Retrospective study:  This large database review was retrospective which makes the jump from association to causation difficult to make and introduces opportunity for bias including the completeness of collected information.
  • Multiple comparisons: The large number of variables evaluated in the initial univariate analysis puts the study at risk for Type II error. The authors did use a conservative estimate to include variables in the multivariable logistic regression but even with such correction the risk of error related to multiple comparisons is quite high.
  • Identifying onset of atrial fibrillation: The ability of patients to accurately identify the onset of atrial fibrillation is debatable and as such the 12 hour cutoff point is difficult to accurately identify.

For a pdf version of this summary click NRC – BoringEM – FinCV

Eve Purdy

Senior Editor at BoringEM
Senior emergency medicine resident and anthropology student-happily consuming, sharing, creating and researching #FOAMed.
BoringEM has been 'bringing the boring' to emergency medicine since 2012. In 2016 this Canadian blog brought its content to CanadiEM.