Lack of Anticoagulation During Cardioversion Increases Risk of Thromboembolic Complications

Cardioverter Defibrillator
Cardioverter Defibrillator
Risk of thromboembolic complications was 5 times higher among patients without therapeutic anticoagulation during cardioversion.

In patients with acute onset atrial fibrillation (AF), the risk of thromboembolic complications was 5 times higher among those who did not receive therapeutic anticoagulation during cardioversion, according to data published in JACC: Clinical Electrophysiology.

Patients who undergo cardioversion within 48 hours of AF onset are considered to be at low risk for thromboembolic complications, although this patient population has been understudied. Therefore, the researchers sought to assess thromboembolism risk after cardioversion within 48 hours of AF onset in patients therapeutically anticoagulated, and compare their risk with those not who did not receive such therapy.

“While current guidelines suggest that one may cardiovert non anticoagulated patients within 48 hours of AF onset, our data would suggest caution in those patients with elevated CHA2DS2-VASc score of 2 or more,” the authors wrote. “Although the total numbers were small, all of our non anticoagulated patients in this study who suffered thromboembolic events post cardioversions had higher CHA2DS2-VASc scores.”

Researchers identified patients undergoing cardioversion within 48 hours after AF onset. Patients were retrospectively reviewed to determine anticoagulation status and major thromboembolic events within 30 days of cardioversion.

Cardioversions were divided into 3 groups based on anticoagulation status at the time of the procedure. Group 1 was composed of patients who were either not taking anticoagulants or on warfarin with INR ≤1.5. They were considered to be “non-anticoagulated.” Group 2 was composed of patients on warfarin with INR between 1.5 and 2, which researchers considered to be “sub-therapeutically anticoagulated.” Finally, the patients in Group 3 were considered “therapeutically anticoagulated” either on warfarn or heparin.

In Group 1, 567 cardioversions were performed in 484 patients without therapeutic anticoagulation (mean CHA2DS2-VASc score: 2.3 ± 1.7). Of these cardioversions, 190 were performed in patients without antiplatelet or anticoagulant agents, 310 patient were only receiving aspirin, and the rest were taking warfarn with INR ≤1.5.

Six patients in this group had neurological events (1.06%), all of whom were on aspirin alone. In comparison to patients without thromboembolic events, these 6 patients had a higher incidence of prior stroke (50.0% vs 6.2%; P<.001) and vascular disease (83.3% vs 38.6%; P=.02).

In Group 2, 116 cardioversions were performed in patients who were subtherapeutic (mean CHA2DS2-VASc score: 2.1 ± 1.6).

In Group 3, 898 cardioversions were performed in 709 patients on therapeutic anticoagulation (mean CHA2DS2-VASc score: 2.6 ± 1.7; P=.017). Among these patients, 567 cardioversions were performed in patients on warfarin who had INR ≥2 and 331 in patients on heparin.

Neurological events occurred in 2 patients (0.22%; odds ratio: 4.8; P=.03) at the time of stroke without anticoagulation. However, there were no thromboembolic events among patients with a CHA2DS2-VASc score less than 2 (P=.06) or in patients with postoperative AF.

Current guidelines regarding anticoagulation use during cardioversion do not provide parameters for defining high and low thromboembolic risk for patients who undergo cardioversion within 48 hours of symptom onset. The results of this study support the use of anticoagulation “at the time of cardioversion and during the post cardioversion period for patients with CHA2DS2-VASc score of 2 and above.”

“In the current era of fast acting oral anticoagulants, it may be wise to initiate such anticoagulants at onset of atrial fibrillation or soon thereafter, before cardioversion, even if cardioversion is done within 48 hours, so as to minimize the risk of thromboembolism after cardioversion,” the authors noted.

In addition, given the increased use of newer anticoagulants or NOACS, it would be particularly valuable to establish treatment protocol for these patients. Researchers clarified that patients with valvular AF or at high bleeding risk were excluded from the study since NOACS have not yet been validated in those populations.

They concluded that the results of the study could help develop risk stratification strategies for thromboembolism using CHA2DS2-VASc scores in patients with AF after cardioversion.


Garg A, Khunger M, Seicean S, Chung MK, Tchou PJ. Incidence of thromboembolic complications within 30-days of electrical cardioversion performed within 48 hours of atrial fibrillation onset. JACC Clin Electrophysiol. 2016. doi:10.1016/j.jacep.2016.01.018.