Editor’s note: This is a series based on work done by three physicians (Patrick Archambault, Tim 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
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.|
|Outcome||Thromboembolic 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
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
- 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