Overall, one-third of thromboembolic events originated from the heart. Left atrial appendage (LAA) and its anatomic complexity has been implicated in 90% of cases of thrombus formation and cardioembolic events in patients with non-valvular atrial fibrillation (AF). Risk scores to predict thromboembolism from AF, such as CHADS₂ and CHA₂DS₂VASc are widely used to guide anticoagulation therapy and varies in relation to comorbidities associated with the thrombogenic substrate; however, because of its clinical conception, they did not include atrial anatomy (atrial enlargement), function (flow velocities) and electrophysiology (atrial fibrillation burden). Patients with CHA₂DS₂VASc score ≥ 2 are at intermediate or higher risk (event rate ≥ 2-3%/year) and anticoagulation is recommended. Left atrial variables such as LAA function and morphology, routinely studied by transesophageal echocardiography (TEE), were not considered in these scores.

In 2012, Di Biase et al.; published a retrospective study of 932 patients with AF and computed tomography (CT)/magnetic resonance imaging (MRI) classification of four different types of LAA morphologies: chicken wing, cactus, windsock and cauliflower. Non-chicken wing categories were 4 to 8 times more likely to have had stroke/TIA. Eight additional cross-sectional studies utilizing this classification for LAA morphology in 2,210 patients (6 with CT and 2 with TEE), found a significant association with non-chicken-wing morphology and stroke in 5 series^– and no significant difference in 3 other studies.^–

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