Earliest Is Best for Preventing Thromboembolism in No-Anticoagulant Acute AF Cardioversion: Cohort Study

August 12, 2014

TURKU, FINLAND — Even if electrical cardioversion of atrial fibrillation (AF) is carried out without anticoagulation within 48 hours of acute-AF onset, the first 12 hours of that period provide by far the best time window of opportunity for diminishing the associated risk of thromboembolic events, suggests a retrospective analysis of >5000 cardioversions carried out from 2003 to 2010 in emergency rooms in Finland[1].

The 30-day risk was 0.7% when cardioversion was achieved within 48 hours and only 0.3% if within 12 hours of AF onset. But the risk went up by a factor of three to four if carried out later within the 48-hour window, report investigators today in the August 13, 2014 issue of the Journal of the American Medical Association, with lead author Dr Ilpo Nuotio (Turku University Hospital, Finland). Only patients with known times from AF onset were included in the study, and all thromboembolic events in the subsequent 30 days were documented by imaging, surgery, or autopsy. About 80% of the events were strokes.

Although the first 48 hours after AF onset is sometimes considered a safe time window for performing cardioversion without anticoagulation, there are few data addressing the issue. Thromboembolic-event rates in the current analysis are comparable to the 0.3% to 0.8% risk for stroke after elective AF cardioversion following three weeks of anticoagulation as cited in the literature by Nuotio et al and compare favorably if cardioversion is achieved within 12 hours.

The analysis from the Finnish CardioVersion (FinCV) study included 5116 successful cardioversions performed in the emergency department without anticoagulation in 2481 adult patients presenting at three centers within 48 hours of onset of acute, symptomatic AF. A third of the cohort was female, and 98% had more than one stroke risk factor.

Of the 38 thromboembolic events within 30 days of cardioversion in 38 patients (0.7%), 31 were strokes (81.6% of events). Thromboembolic event rates by time from AF onset to cardioversion were:

  • 0.3% for <12 hours (n=2440).

  • 1.1% for 12 to <24 hours (n=1840).

  • 1.1% for 24 to <48 hours (n=836).

  • 0.7% for <48 hours across the entire cohort.

Adjusted Odds Ratio (OR, 95% CI) for Thromboembolic Events 30 Days After Acute-AF Cardioversion Without Anticoagulation

Time From AF Onset to Cardioversion OR (95% CI)* p
12–24 h vs <12 h 4.0 (1.7–9.1) 0.001
24–48 h vs <12 h 3.3 (1.3–8.9) 0.02
*Adjusted for age, sex, and presence of heart failure or diabetes

The authors reported no conflicts of interest.

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