Interpretation depends on both when bubbles appear and where they are seen. Bubbles reaching the left heart can indicate that blood bypassed the expected pulmonary filtering route, while their distribution helps direct attention toward an intracardiac or intrapulmonary pathway. This combined pattern is more informative than simply recording that bubbles crossed to the left side.
The pulmonary circulation normally acts as a filter for the transient bubbles created in the saline-air mixture. Consequently, bubbles confined to the right heart follow the expected route, whereas left-sided appearance suggests an abnormal passage. This principle allows echocardiography to investigate shunting by observing bubble transit rather than relying only on structural cardiac images.
The key distinction is anatomical: an intracardiac shunt permits bubbles to cross within the heart, whereas an intrapulmonary pathway allows them to reach the left heart through pulmonary vascular connections. Echocardiographers use the observed chamber location and timing to determine which pathway is more consistent with the study, helping focus evaluation of abnormal circulation.
During the examination, saline is mixed vigorously with air to create transient microbubbles and then injected intravenously while echocardiographic images are acquired. The operator follows their movement into the right heart and evaluates whether they later appear in the left heart. This sequence provides the observations needed to assess abnormal blood flow across cardiac or pulmonary pathways.
Agitated Saline Contrast can be performed during either transthoracic or transesophageal echocardiography. In both settings, imaging provides a real-time view for tracking bubbles through the cardiac chambers and assessing their location. The contrast study therefore complements the echocardiographic examination by adding information about blood-flow pathways that may not be evident from structural imaging alone.
Clinicians may use the study when unexplained hypoxemia, embolic events, or suspected congenital heart disease raises concern for abnormal circulation. Findings can support evaluation for a patent foramen ovale, atrial septal defect, or pulmonary arteriovenous connection. Thus, the test links a clinical problem with evidence of a possible right-to-left passage seen during echocardiography.