Poor Distal Left Atrial Appendage Opacification on Early-Phase Cardiac CTA and Association With Arterial Thromboembolism

BACKGROUND: Poor contrast opacification (PCO) of the distal left atrial appendage (LAA) on early-phase cardiac computed tomography angiography (CTA) may reflect impaired LAA hemodynamics and blood stasis, potentially predisposing to thrombus formation and embolic events. Thus, this study aimed to evaluate the association between early-phase LAA-PCO and arterial thromboembolic events in patients with non-valvular atrial fibrillation (AF). METHODS: In this single-center retrospective cohort study, 389 consecutive adult patients with non-valvular AF who underwent cardiac CTA were analyzed between January 2020 and December 2023. Qualitative LAA-PCO on early-phase CTA and quantitative Hounsfield unit (HU) measurements at the LAA ostium, mid-body and distal LAA, left atrium (LA), and descending aorta (DA) were recorded. The O/D ratio (LAA-ostium HU/distal LAA HU) and a corrected O/D ratio normalized by LA/DA attenuation were calculated. Associations with ischemic stroke and other arterial embolic events were assessed using multivariate logistic regression, and model discrimination was assessed using the C-index. RESULTS: Of the 389 patients, 104 experienced arterial embolic events, including 102 ischemic strokes. LAA-PCO was present in 68 patients (17.48%) and was more common in the embolic group (27.88% vs. 13.68%, p = 0.001). The embolic group had significantly lower distal LAA HU and higher O/D and corrected O/D ratios. In the multivariate analysis, the CHA₂DS₂-VASc score (odds ratio (OR) = 2.442; p = 0.001), LAA-PCO (OR = 2.120; p = 0.014), O/D ratio (OR = 1.250; p = 0.004) and corrected O/D ratio (OR = 1.325; p = 0.002) were independently associated with arterial embolism. A model combining the CHA₂DS₂-VASc score and the corrected O/D ratio showed a relatively high C-index of 0.87. CONCLUSIONS: Poor distal LAA opacification on early-phase CTA is associated with arterial thromboembolism in patients with non-valvular AF and may provide complementary information to the CHA₂DS₂-VASc score for thromboembolic risk assessment. Prospective validation and standardization of computed tomography (CT) protocols are needed before clinical implementation.