Left Atrial Thrombus on Oral Anticoagulant Therapy

Study Questions:

Is the prevalence of left atrial appendage (LAA) thrombus lower in patients taking novel oral anticoagulants (NOACs) than in those taking warfarin?


This is a retrospective study in patients (n = 388; median age 65 years; CHA2DS2-VASc score ≤2 in 62%; paroxysmal AF in 53%) undergoing transesophageal echocardiography (TEE) prior to catheter ablation of atrial fibrillation (AF). TEE was performed within 3 days of the ablation procedure. Patients who had not been taking oral anticoagulants (OACs) for at least 4 weeks were excluded. OAC therapy was not interrupted leading up to TEE.


The duration of OAC was longer in patients taking warfarin as compared to NOACs. The mean CHA2DS2-VASc score was higher in the former. The prevalence of LAA thrombus was 4.4% and 2.9% in patients taking a NOAC and warfarin, respectively (p = 0.45). Among those taking a NOAC, the prevalence of thrombus was 5.4%, 4.8%, and 0% in patients on dabigatran, rivaroxaban, and apixaban, respectively (p = 0.48). Presence of heart failure and persistent AF was independently associated with LAA thrombus. OAC regimen was modified in patients with LAA thrombus, and repeat TEE showed resolution of thrombus in the majority.


The rate of thrombus detection in patients presenting for AF ablation is similar among those taking NOACs and warfarin. The authors concluded that a preprocedure TEE is still necessary to rule out LAA thrombus irrespective of the OAC regimen.


NOACs in general have been found to be superior to warfarin both in terms of safety, and likely efficacy. It is not unreasonable, thus, to suspect that the rate of LAA thrombus formation may be lower in the former, which may obviate the need for a preprocedure TEE. However, the results of the study show that there is no significant difference in the rates of thrombus detection between the two strategies, and that a TEE is still useful given a prevalence of thrombus of 3-5%. In patients with paroxysmal AF who have been taking OACs for at least 4 weeks prior, but without heart failure, stroke, or advanced age, it is reasonable to proceed with catheter ablation without a TEE. The rate of thrombus formation in those taking a NOAC may even be higher since the drug is discontinued (unlike warfarin) for a few doses prior to the ablation procedure. The prevalence is likely to be higher in both groups among those presenting for elective cardioversion, as opposed to those for catheter ablation, since the latter are in general healthier.

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Anticoagulation Management and Atrial Fibrillation, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Appendage, Atrial Fibrillation, Catheter Ablation, Echocardiography, Echocardiography, Transesophageal, Electric Countershock, Heart Failure, Stroke, Thromboembolism, Thrombosis, Vitamin K, Warfarin

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