Introduction
Atrial fibrillation (AF) is among the major risk factors for
intracardiac thrombi that can lead to cerebral or systemic
embolism.1 The majority of intracardiac thrombi are
formed inside the left atrial appendage (LAA) due to turbulence and
lower blood flow rates, particularly during AF.2,3Meanwhile, catheter ablation (CA) has become the first AF treatment
choice in the last few decades. Prior to CA, when a thrombus is present
in the LAA, safety evaluations must be performed, particularly in
patients with persistent or long-standing persistent AF. Although the
gold standard for the detection of intracardiac thrombi is
transesophageal echocardiography (TEE), this method is associated with
occasional technical and appraisal
difficulties.
Contrast computed tomography (CT) is another standard method used for
the detection of intracardiac thrombi and has the potential to replace
TEE. Compared to TEE, CT is easier to perform and is related to lower
levels of discomfort among physicians. Additionally, the level of
difference observed in the evaluation of CT images is much lower than
that in TEE. However, similar to TEE, CT can still show false-positive
results under conditions of low blood flow or stasis in the LAA. In
these situations, the contrast medium hardly fills the whole LAA,
particularly the edge of LAA, at the time of CT. Some reports have shown
that CT performed in the prone position is more useful in the
differentiation of thrombi from stasis than scans performed in the
supine position, as gravity can increase the spread of contrast dye into
the top area of the LAA.4,5 It has been suggested that
contrast CT conducted in the delayed or late phase yields improved
accuracy in the detection of thrombi than that performed in the early
phase.6-8 However, neither method is completely
exclusive of false-positive results, and
there is currently no known method
that combines late-phase contrast CT and prone-position contrast CT
(late-pCT) in this setting.
Therefore, with the aim of minimizing the rate of false-positive
results, we sought to investigate
the diagnostic accuracy of late-pCT in the detection of thrombi in the
LAA among patients with persistent or long-standing persistent AF prior
to CA and re-evaluated the LAA by intracardiac echocardiography (ICE)
during CA.