Key Points
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An estimated 47% of thrombi in valvular atrial fibrillation (AF) and 91% of thrombi in nonvalvular AF are localized in the left atrial appendage (LAA)
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LAA flow stasis (or spontaneous echocardiographic contrast; SEC) is a pattern of blood flow (echogenicity) attributed to ultrasonic backscatter from blood cell aggregates that form under low shear conditions
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SEC is formed through protein-mediated (particularly fibrinogen) red cell aggregation promoting red cell rouleaux formation, and is the cardiac factor most-strongly associated with LAA thrombus formation
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Transoesophageal echocardiography is the gold standard for the evaluation of LAA stasis and thrombosis, and promising results have been reported for intracardiac echocardiography and transthoracic echocardiography with contrast
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Cardiac CT is an accurate, noninvasive imaging modality for the detection of LAA thrombi, particularly when delayed imaging acquisition protocols are used
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Prospective studies to validate the use of cardiac MRI for LAA assessment are needed, because this technique avoids the use of ionizing radiation and iodinated contrast media
Abstract
Atrial fibrillation (AF) is the most-common arrhythmia in the elderly population (age >65 years). The left atrial appendage (LAA) is the main location of thrombus formation, predominantly in patients with nonvalvular AF. This Review is focused on the pathophysiology, assessment, and clinical implications of stasis (or spontaneous echocardiographic contrast; SEC) and thrombus formation in the LAA. The gold-standard modality for assessment of SEC and thrombus in the LAA is echocardiography, particularly transoesophageal echocardiography (TEE). Cardiac CT (CCT) is an accurate, noninvasive alternative to TEE for the detection of LAA thrombi, distinctly when delayed-imaging acquisition protocols are used. Prospective studies to validate the use of cardiac MRI (CMR) for this purpose are needed, and will avoid the need for radiation and iodinated contrast. CCT or CMR could potentially be implemented to rule out LAA thrombus, avoiding unnecessary preprocedural TEE. Cardiac imaging is also of primary importance in the setting of LAA closure devices and electrophysiological studies. New trials are needed to compare the various imaging modalities, with surgicopathological findings as a reference standard.
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Romero, J., Cao, J., Garcia, M. et al. Cardiac imaging for assessment of left atrial appendage stasis and thrombosis. Nat Rev Cardiol 11, 470–480 (2014). https://doi.org/10.1038/nrcardio.2014.77
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DOI: https://doi.org/10.1038/nrcardio.2014.77
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