2. Ascending SVC thrombus

Point of care ultrasound examination of the patient’s right lateral neck revealed a rhythmic, target shaped change in echo density over time from anechoic to hyper-echoic with a frequency of approximately one cycle per second. The ICU team confirmed that the swelling of the patient’s right breast and upper extremity were due to an ascending thrombus from the patient’s chronic SVC syndrome with CT scan. This ultrasound exhibits classic findings of spontaneous echo contrast (SEC). SEC, or “Smoke”, is caused by layering of cellular components of blood during states of blood flow ranging from low-velocity blood flow to complete stasis (1). It is frequently seen in the left atrial appendage in patients with atrial fibrillation, but can be seen in any component of the cardiovascular system (2). SEC present in vasculature outside the heart can signal that a thrombus is rapidly forming, and can prompt the discussion of initiating further imaging studies to evaluate more proximal veins in the chest that cannot be seen with conventional ultrasound, or initiation of anticoagulation before a thrombus truly forms. While uncommonly visualized in vascular ultrasound, this finding can be very useful in early diagnosis of intravascular thrombi.


Spontaneous echo contrast was discovered in a series of animal studies in 1981 that blood will become more echogenic during periods of stasis when visualized with high frequency (~7.5MHz) transducers (3). The term “spontaneous echo contrast” as an ultrasonographic finding was first used in the American journal of Cardiology in 1992 as a phenomenon caused by increased ultrasonic back-scatter when red blood cells interact with plasma proteins in states of low flow or shear (1).


  1. Merino A, Hauptman P, Badimon L, Badimon JJ, Cohen M, Fuster V, Goldman M. Echocardiographic "smoke" is produced by an interaction of erythrocytes and plasma proteins modulated by shear forces. J Am Coll Cardiol. 1992;20(7):1661-8. [CrossRef] [PubMed]
  2. Siddiqui MA, Holmberg MJ, Khan IA. Spontaneous echo contrast in left atrial appendage during sinus rhythm. Tex Heart Inst J. 2001;28(4):322-3. [CrossRef]
  3. Sigel B, Coelho JC, Spigos DG, et. al. Ultrasonography of blood during stasis and coagulation. Invest Radiol. 1981;16(1):71-6. [CrossRef] [PubMed]

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