An atrial septal defect, or ASD, is an opening in the septum, or wall, that separates the left and right atria of the heart. This hole allows oxygenated blood from the left atrium to flow into the right atrium, increasing the workload on the right side of the heart and the lungs. On echocardiography, an ASD can be directly visualized as a gap in the atrial septum, and color Doppler shows the abnormal flow of blood crossing from left to right through the defect. ASDs are among the most common congenital heart defects and can sometimes go undetected until adulthood. Echocardiography, including both transthoracic and transesophageal approaches, is the primary method for diagnosing and sizing these defects.
Sonography Term