Abstract:
Background: Non-valvular atrial fibrillation (NVAF) is a highly
prevalent arrhythmia where loss of synchronized atrial contraction
increases the risk of intracardiac thrombus particularly within the left
atrial appendage (LAA). Anticoagulation is the mainstay of stroke
prevention based on the CHA2DS2-VASc score; however, it does not account
for LAA structural characteristics.
Methods: The research comprises a retrospective matched
case-control study of 196 subjects with NVAF who underwent
transesophageal echo (TEE). The control group, without thrombus (n=117),
was selected from two different groups, both pools had: NVAF and
CHA2DS2-VASc score ≥ 3. One group underwent screening TEE prior to
Watchman closure device placement from January 2015 to December 2019
(n=74) the second underwent TEE prior to cardioversion from February to
October 2014 (n=43). The study group, with thrombus (n=79), included
patients with NVAF, TEE study performed between February 2014 and
December 2020, and LAA thrombus. The propensity score method was
utilized to determine the matched controls while accounting for
confounding from prognostic variables resulting in 61 matched pairs
included in the analysis data set. LAA ostial area (OA) (calculated from
orthogonal measurements 0, 90° or 45, 135°), LAA maximal depth, and peak
LAA outflow velocity were measured.
Results: Patient characteristics and TEE data were collected
(Table I) and compared using the t-test or chi-square analysis. We
observed a lower LAA peak exit velocity in the thrombus group as
compared to the control group. Additionally, we found that patients in
the thrombus group had smaller LAA OA at 0 and 90 degrees, at 45 and 135
degrees, using largest diameter, as well as using aggregate OA, and
smaller maximum LAA depth compared to patients in the control group.
Candidate conditional logistic regression models for the outcome of
presence of thrombus were evaluated (Table II). Statistical results from
the best-fitting conditional regression model were calculated (Table
III) showing a significant association between aggregate OA and LAA exit
velocity with presence of thrombus.
Conclusion: Utilizing LAA structural characteristics to predict
thrombus formation may help refine current cardioembolic stroke (CES)
risk estimation.