TEE and contrast-enhanced CT examination
TEE was performed within 24 hours of ablation. After local pharyngeal anesthesia, the transducer was inserted into the midportion of the esophagus. We assessed the presence of intra-LA thrombus, left atrial appendage (LAA) orifice area, LAA flow velocity, spontaneous echocardiography contrast (SEC), and LA-right atrium shunt using a multiplane transesophageal transducer connected to an ultrasound system (Vivid E95, GE Vingmed Ultrasound AS, Horten, Norway). The LAA flow velocity was assessed using the pulsed Doppler method, with the sample volume placed within the LAA cavity. The peak LAA in- and outflow emptying velocities were analyzed for at least five cardiac cycles, and mean values were calculated. A thrombus was defined as an echo-dense mass adherent to the cavity showing independent motion or different echogenicity that could be distinguished from the surrounding endocardium or pectinate muscles observed in multiple planes. The SEC was defined as dynamic, “smoke like” swirling patterns of echogenicity in the LA and LAA distinct from white-noise artifacts after gain setting adjustment to eliminate background noise. The SEC severity was divided into 5 grades (0: none to 4: severe) according to the echo density and the extent of SEC in the LA and LAA cavities.8 The absence/presence of thrombi and SEC were confirmed by at least two investigators who were blinded to the baseline characteristics of the patients and related outcomes.
Contrast-enhanced CT imaging was also scheduled before the procedure in all cases if applicable. Although the CT image was primarily used for spatial reorganization of the 3D image of the LA during the mapping procedure, it is also useful to evaluate the absence of the LA and LAA thrombi in a delayed contrast image since it has a high negative predictive value.9 We offered both TEE and contrast-enhanced CT imaging for most patients undergoing first catheter ablation for AF; however, some patients who could not be examined by TEE for any reason underwent CT imaging study only to confirm the absence of thrombi. In contrast, when thrombi were suspected on the CT image, a final decision for the presence of thrombi was made using TEE in all cases. If patients could not be examined by both TEE or CT imaging, ICE was used to evaluate thrombi during the ablation procedure. The presence or absence of LA thrombi on all CT images was reviewed and diagnosed by a radiologist who was blinded to the patient characteristics.