Description of a phenomenon resembling spontaneous echocardiographic contrast in the venous system

Introduction. - According to Beppu et al., spontaneous echocardiographic contrast (SEC or smoke) is a pattern of "spontaneous swirling echoes originally visualized by transthoracic echocardiography in the enlarged left atrium of patients with mitral stenosis" (J Am Cardiol 1985;6:744-749). It has since been primarily associated with atrial fibrillation and flutter. The clinical significance of SEC is its association with left atrial thrombus, increased thromboembolic complications, and death. The pathogenesis of SEC seems to involve Rouleau formation between red cells and fibrinogen at low shear rates, which is an in vitro equivalent of blood stasis. Black noted that "Red cell aggregation, manifested as SEC, appears to be a precursor to thrombosis. Left atrial thrombi are rich in fibrin and red cells, resembling venous more than arterial thrombi" (Echocardiography 2000;17(4):373-382). Methods. - If left atrial thrombi are associated with SEC and resemble venous thrombi, it was hypothesized that actual venous thrombi in previously undescribed locations, most notably deep vein thrombosis, may equally be associated with SEC. We asked our coauthors (H.T. and M-C.Y.) to search for such a phenomenon among patients referred to the vascular laboratory for suspected venous thrombosis. Case Presentation. - In the following case series, we report an original phenomenon of swirling echogenicity in the venous system that we believe is SEC. The phenomenon was fairly rare (maximum 1.5% of referred patients, whereas deep venous thrombosis itself was 15-20%). The clinical significance of this phenomenon is discussed.