• atrium;
  • fibrillation;
  • thrombus;
  • catheter ablation;
  • echocardiography

Introducton:A 10% incidence of left atrial (LA) thrombus formation has been detected using intracardiac echocardiography (ICE) imaging monitoring during LA ablation for atrial fibrillation (AF). The aim of this study was to determine if the intensity of anticoagulation reduces LA thrombus formation during pulmonary vein isolation procedure in patients with AF and spontaneous echo contrast (SEC).

Methods and Results:We studied 511 patients (age 56 ± 10 years) undergoing pulmonary vein ostial isolation/ablation using radiofrequency energy. SEC was detected in 179 of 511 patients with ICE imaging before dual transseptal catheterization. All patients were anticoagulated with heparin to achieve activated clotting time (ACT) 250–300 seconds (group I) or >300 seconds (group II) confirmed at 30-minute intervals. SEC was detected in 49/294 (16.7%) patients in group I versus 130/217 (59.9%) in group II (P < 0.0001). LA thrombus was observed in 33/294 (11.2%) patients in group I versus 6/217 (2.8%) in group II (P < 0.05). For those patients with SEC, LA thrombus was observed in 22/49 (44.9%) in group I versus 2/61 (4.6%) in group II (P < 0.0001). There were no significant differences in age, number of unsuccessful drugs, persistent AF, left ventricular ejection fraction, and LA diameter between the two groups. No clinical embolic event was observed with withdrawal of LA thrombus to the RA.

Conclusion:ICE-diagnosed SEC before transseptal catheterization identifies an increased risk of LA thrombus. Increased intensity of heparin anticoagulation (ACT >300 seconds) during LA ablation for AF may prevent LA thrombus formation especially in patients with SEC.