Lack of anticoagulants after cardioversion of acute AF may increase complications

When no anticoagulation is used after cardioversion of acute atrial fibrillation, patients with conventional risk factors for thromboembolism are at increased risk for stroke and other thromboembolic events, according to results from a large retrospective study.

The researchers who conducted the FinCV study concluded that their data support a European Society of Cardiology guideline issued in 2010 recommending anticoagulation therapy during and after cardioversion in patients with acute AF and risk factors for stroke. The specific therapy recommended is heparin peri-cardioversion followed by long-term anticoagulation with a vitamin K antagonist.

In FinCV, researchers followed clinical outcomes from successful cardioversions (n=5,116) in patients treated for AF lasting less than 48 hours before treatment. The patients were identified from the discharge registries at three hospitals in Finland. Emergency clinic admission records and databases were then used to review all patients (aged older than 18 years) with acute AF who underwent cardioversion during the study period from 2003 to 2010. Further analysis was conducted on the patients (n=2,481, 63.7% men) who did not receive anticoagulation therapy during or after treatment. The primary outcome of interest was definite thromboembolic event — defined as confirmed stroke caused by cerebral infarction or confirmed systemic embolism — within 30 days after index cardioversion.

Determination of risk

There were 38 (0.7%) definite thromboembolic events within 30 days after cardioversion (median time, 2 days). Thirty-one events were stroke. Additionally, four patients had a transient ischemic attack after cardioversion.

Using classification tree analysis, the researchers determined that the highest risk for thromboembolism (9.8%) was present in patients with HF and diabetes, whereas the lowest risk (0.2%) was present in patients aged younger than 60 years with no HF.

The only independent predictors of embolic events were age (OR=1.05; 95% CI, 1.02-1.08), female sex (OR=2.1; 95% CI, 1.1-4), HF (OR=2.9; 95% CI, 1.1-7.2) and diabetes (OR=2.3; 95% CI, 1.1-4.9), according to logistic regression analyses.

Despite just a 0.7% occurrence of embolic events within 30 days after cardioversion of acute AF in patients not administered anticoagulants, the risk is too high not to give anticoagulants to patients with risk factors for stroke, the researchers wrote. “[I]ncreasing age, female gender, heart failure and diabetes increase the risk of thromboembolic complications substantially, and in the presence of multiple risk factors, the risk becomes unacceptably high (~10%), being significantly higher than after elective cardioversion of AF when using conventional pre- and post-cardioversion anticoagulation.”

Future implications

In a related editorial, Nikolaos Dagres, MD, a cardiologist at the University of Athens, Greece, and colleagues said these results have important clinical implications and provide further knowledge about the incidence and risk factors for thromboembolic complications after cardioversion of acute AF.

“[These results] prove the correctness of the current [European] guidelines,” the authors wrote.

Although the study may be limited due to the retrospective design, it is mitigated by the large number of patients and the good quality of the analyzed registries. Also, a prospective randomized trial may be unethical, Dagres and colleagues wrote.

For more information:

Airaksinen KEJ. J Am Coll Cardiol. 2013;doi:10.1016/j.jacc.2013.04.089.

Dagres N. J Am Coll Cardiol. 2013;doi:10.1016/j.jacc.2013.06.019.

Disclosure: The researchers and editorial authors report no relevant financial disclosures.