Echocardiography
LA size and left ventricular ejection fraction (LVEF) were assessed by
transthoracic echocardiography (TTE) when available prior to the
ablation. All TEEs were performed immediately before the planned
ablation procedure. LA size and LAA velocities were assessed, and the LA
and LAA were examined for the presence of thrombus or spontaneous echo
contrast (SEC). In addition, the presence of patent foramen ovale (PFO)
or atrial septal defect was assessed with color Doppler and/or injection
of agitated saline. TEEs were interpreted independently by experienced
cardiologists specializing in echocardiography.
Cardiac Computed Tomography
CT images were obtained on the day of ablation using a 320-detector
scanner (Aquilion ONE, Canon Medical Systems) and prospective scan
acquisition targeted at 40% of the R-R cycle (end-systole) without
padding. Computed tomographic angiography (CTA) of the heart and great
vessels was performed with intravenous iodinated contrast, including 3D
iterative reconstruction of the cardiac chambers at 40% of the R-R
interval. Prospective ECG-gating was performed to reduce the effective
radiation dose. CTA was optimized for imaging the cardiac chambers and
great vessels but not to visualize the complete course of the coronary
arteries. A second acquisition was performed 30 seconds after the
primary acquisition to assess for adequate filling of the left atrial
appendage. A LA/LAA thrombus was defined as an intracavitary contrast
filling defect with attenuation values similar to non-enhanced tissue.
Intracavitary thrombi were differentiated from normal pectinate muscles
and from filling, motion, and acquisition artifacts.