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.