Background:
In atrial fibrillation (AF), thrombus formation typically occurs within
the left atrial appendage (LAA) and is less common in the left atrial
cavity (LAC)1-3. Based on transesophageal
echocardiography (TEE), the prevalence of LAA thrombus in AF patients in
the absence of anticoagulation is 7.5%, with a 1.8% prevalence of LAC
thrombus4, though extra-appendage thrombus appears to
be a rare finding in non-valvular atrial
fibrillation5. LAA/LAC thrombus may be associated with
embolization to the brain, causing stroke. The LAA has distinct
structural, anatomic, and physiologic properties that permit the
structure to serve its role as a decompression chamber during periods of
elevated left atrial pressure. The volume, orifice size, length, shape,
and lobulation of the LAA may vary markedly between
individual6, 7.
The pathogenesis of thrombus formation in the LAA in the setting of
non-valvular AF (NVAF) is not fully understood. Investigators have
examined structural and functional characteristics of the LAA and how
they contribute to LAA thrombus formation and cardioembolic stroke (CES)
risk. Reduced blood inflow and outflow velocities at the LAA orifice
based upon Doppler transesophageal echocardiography (TEE) measurements
have predicted LAA thrombus risk8. More recent studies
seeking to correlate descriptive LAA morphologies with thromboembolic
risk have reported lower risks of embolic events with Chicken-Wing LAA
morphology7-9.
The LAA anatomic determinants that predict thromboembolic risk in NVAF
have not been completely elucidated. This study aimed to compare the LAA
orifice size, maximal depth, and peak exit velocities between AF
patients with LAA thrombus and high-risk AF patients without thrombus.
Identifying novel LAA anatomic determinants of thrombus formation may
help stratify AF thromboembolic risk in the future.