Left atrial thrombus associated with ablation for atrial fibrillation: Identification with intracardiac echocardiography

OBJECTIVES This study reports the incidence of, risk factors for, and management of left atrial (LA) thrombus documented by intracardiac echocardiography (ICE) during LA ablation for atrial fibrillation (AF). BACKGROUND Thrombus formation is a risk associated with LA ablation procedures. METHODS Intracardiac echocardiography imaging was performed in 232 patients (184 men, average age 55 +/- 11 years) with AF undergoing pulmonary vein ostial ablation. RESULTS Anticoagulation (activated clotting time >250 s) was maintained after dual transseptal catheterization. Left atrial thrombus (n = 30) was observed in 24 of 232 patients (10.3%). Thrombi measured 12.9 +/- 11.1 min (length) and 2.2 +/- 1.3 mm (width) and were attached to a sheath or mapping catheter. Most thrombi (27 of 30, 90%) were eliminated from the LA by withdrawal of the sheath and catheter into the right atrium (RA). Two thrombi became wedged in the interatrial septum and incompletely withdrawn into the RA, and one was recognized only on post-procedure review of ICE images. Patients with LA thrombus had an increased LA diameter (4.8 +/- 0.5 vs. 4.5 +/- 0.6 cm, p < 0.02), spontaneous echo contrast (67% vs. 3%, p < 0.0001) and a history of persistent AF (29% vs. 6%, p < 0.0002). Multivariate discriminant analysis showed that spontaneous echo contrast (f = 97.9, p < 0.0001) was the most important determinant of LA thrombus formation. No patient with LA thrombus suffered a clinical thromboembolic complication. CONCLUSIONS Left atrial thrombus identified on ICE may occur during LA catheter ablation procedures despite aggressive anticoagulation. Spontaneous echo contrast may predict risk for LA thrombus formation. Left atrial thrombus may be successfully withdrawn into the PA under ICE imaging with no overt complications. (C) 2004 by the American College of Cardiology Foundation.