Smoke on TEE

Q: What does the finding of spontaneous echocardiographic contrast (SEC) or "smoke" signify on transesophageal echocardiogram (TEE)?

Answer: 

Spontaneous echocardiographic contrast (SEC), popularly known as "smoke," refers to the presence of dynamic, smoke-like echoes seen during TEE, mainly in the left atrium, but can be seen in any chamber.

SEC signifies increased erythrocyte aggregation caused by low shear rate due to altered flow dynamics. Erythrocyte aggregation is mediated by plasma proteins, especially fibrinogen, which promotes red cell rouleaux formation by moderating the normal electrostatic forces (due to negatively charged membranes) that keep erythrocytes from aggregating. SEC is usually a preceding stage of thrombus formation.

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References:

1. Black IW, Chesterman CN, Hopkins AP, et al. Hematologic correlates of left atrial spontaneous echo contrast and thromboembolism in nonvalvular atrial fibrillation. J Am Coll Cardiol 1993; 21:451.

2. Gedikli Ö, Mohanty S, Trivedi C, Gianni C, Chen Q, Della Rocca DG, Burkhardt JD, Sanchez JE, Hranitzky P, Gallinghouse GJ, Al-Ahmad A, Horton R, Di Biase L, Natale A. Impact of dense "smoke" detected on transesophageal echocardiography on stroke risk in patients with atrial fibrillation undergoing catheter ablation. Heart Rhythm. 2019 Mar;16(3):351-357. doi: 10.1016/j.hrthm.2018.10.004. Epub 2018 Oct 9. PMID: 30312757.

3. Fatkin D, Loupas T, Low J, Feneley M. Inhibition of red cell aggregation prevents spontaneous echocardiographic contrast formation in human blood. Circulation 1997; 96:889.

4. Black IW. Spontaneous echo contrast: where there's smoke there's fire. Echocardiography. 2000 May;17(4):373-82. doi: 10.1111/j.1540-8175.2000.tb01153.x. PMID: 10979010.