A simple technique for detecting small defects of the atrial septum

A sensitive technique for detecting small defects of the atrial septum is described. A Valsalva maneuver is used to cause right atrial pressure to exceed left atrial pressure. This reversal of the normal interatrial pressure gradient causes a transient right to left shunt across the defect. The right to left shunt is detected by noting an early appearance deflection in standard indicator-dilution curves performed by injecting indocyanine green dye into the inferior vena cava during the Valsalva maneuver. By means of this technique, 7 of 8 surgically induced defects, from 1 to 12 mm in diameter, were detected. There were no false positive results among 9 control animals with an intact atrial septum. This technique presents a sensitive and simple method for detecting small atrial septal defects. The only equipment required is that used to perform standard indicator-dilution curves.