Negative Contrast Echocardiography for the Diagnosis of Atrial Septal Defects

Abstract

In 1968, Gramiak et al., reported that rapid intracardiac injection of a variety of substances, including saline and indocyanine green dye, produced a cloud of echoes at the injection site which, one formed, would follow the path of blood flow downstream [1]. It was further noted that these intravascular echoes disappeared during passage through either the systemic or pulmonary capillary beds [2] and, thus, were normally confined to the side of the circulation in which they were generated. Based on these observations, it was suggested that the unexpected appearance of echocardiographic contrast crossing intracardiac septa might be used as evidence of an intracardia shunt. Subsequent reports confirmed the sensitivity of echocardiographic contrast as a means of detecting both intra and extra-cardiac shunts [3–7] and demonstrated that shunts as small as 5% of the systemic blood flow could be appreciated [5].