Left Atrial Thrombus Detected in Atrial Fibrillation Patients Even After NOAC Therapy

After ≥4 weeks of continuous anticoagulation therapy, left atrial thrombus was still detected in patients with atrial fibrillation or atrial flutter.

In patients with atrial fibrillation (AF) or atrial flutter, left atrial (LA) thrombus may still be detected via transesophageal echocardiography (TEE), despite ≥4 weeks of non-vitamin K antagonist oral anticoagulant (NOAC) therapy.

Researchers sought to determine whether or not TEE was required for patients prior to catheter ablation of AF or atrial flutter, and to compare LA thrombus rates and dense spontaneous echocardiographic contrast (SEC) in patients on NOACS vs warfarin. Their findings were published in JACC: Clinical Electrophysiology.

“To our knowledge,” they wrote, “this is the first study to systematically examine the prevalence of LA thrombus and dense SEC prior to catheter ablation of AF and atrial flutter among fully anticoagulated patients on NOAC therapy.”

Initially, researchers evaluated 627 patients undergoing first TEE at New York Presbyterian Hopsital-Weill Cornell. After exclusion, a total of 388 patients (median age: 65 years; 74% male) on ≥4 weeks of continuous NOAC (n=183) or warfarin therapy (n=205) were selected. TEEs were performed within 3 days of catheter ablation. Follow-up data on stroke, transient ischemic attack (TIA), and systemic embolic events were assessed within 30 days of the procedure.

CHA2DS2–VASc scores ranged from 52 (13%) patients with a score of 0, 87 (22%) with a score of 1, 103 (27%) with a score of 2, and 146 (38%) with a score ≥3. Patients on warfarin had significantly higher CHA2DS2–VASc scores compared to patients on NOACS (P<.001).

Patients on warfarin also had significantly more congestive heart failure, hypertension, coronary or vascular disease, and prior mitral valve surgery compared with patients on NOACS.

The prevalence of LA thrombus was 3.6%, LA thrombus/dense SEC and LA thrombus was 6.2%, and LA thrombus/any SEC was 14.2% among patients after ≥4 weeks of continuous anticoagulation therapy. Catheter ablation was postponed in all patients with LA thrombus and in 2 patients with dense SEC.

LA thrombus and LA thrombus/dense SEC detection rates were similar between patients on NOACS vs warfarin (LA thrombus: 4.4% vs 2.9%; P=.45; LA thrombus/dense SEC: 6.0% vs 6.3%; P=.89), as assessed by TEE. However, there was a higher prevalence of LA thrombus/any SEC detection in patients on warfarin compared with patients on NOACS (18% vs 9.8%; P=.021).

The rates of LA thrombus detection by individual NOAC therapy were 5.4% on dabigatran (n=93), 4.8% on rivaroxaban (n=62), and 0% on apixaban (n=28; P=.48). Similarly, the rates of LA thrombus/dense SEC detection were 6.5% on dabigatran, 8.1% on rivaroxaban, and 0% on apixaban (P=.34). Finally, LA thrombus/any SEC detection rates were 10.8% on dabigatran, 11.3% on rivaroxban, and 3.6% on apixaban.

Researchers identified congestive heart failure, decreased left ventricular ejection fraction (<55%), persistent AF, and moderate-to-severe LA enlargement as “significant univariate predicators of LA thrombus detection on pre-ablation screening TEE.”

Follow-up data was available on 98% of patients who underwent catheter ablation. Two patients had a stroke, TIA, or systemic embolic event within 30 days of their procedure.

“Despite a minimum of 4 weeks of continuous anticoagulation, the rates of LA thrombus and LA thrombus/dense SEC among patients on NOAC therapy undergoing TEE prior to catheter ablation of AF or atrial flutter are not zero (4.4% and 6%, respectively),” researchers concluded. “The rates of LA thrombus and dense SEC detection among patients on NOACS and warfarin were comparable.”

Future studies should examine the rates of LA thrombus detection among patients placed on NOAC therapy. Any differences found between individual NOAC agents should be further explored to compare their anti-thrombotic properties.


Frenkel D, D’Amato SA, Al-Kazaz M, et al. Prevalence of left atrial thrombus detection by transesophageal echocardiography: a comparison of continuous non-vitamin K antagonist oral anticoagulant vs warfarin therapy in patients undergoing catheter ablation for atrial fibrillation. JACC Clin Electrophysiol. 2016. doi: 10.1016/j.jacep.2016.01.004.