Two-dimensional contrast echocardiography with carbon dioxide in the detection of congenital cardiac shunts.

Medically pure (100%) carbon dioxide directly injected into a peripheral vein was used for 2-dimensional contrast echocardiography in 134 patients with an arteriovenous shunt demonstrated by cardiac catheterization and cineangiography, Qp/Qs ratios of 1.5 to 3.7, pulmonary-to-systemic peak systolic pressure ratios of 0.2 to 0.8 and no oximetrically demonstrable venoarterial shunt. Two patients with transposition of the great arteries, intact ventricular septum and a Senning operation as well as 30 normal subjects of comparable age also were studied. In patients with an atrial septal defect, the gas microbubbles opacified the left atrium. In patients with a ventricular septal defect, the gas microbubbles opacified the left ventricle, whereas the left atrium was free of contrast. In all patients with patent ductus arteriosus, the gas microbubbles opacified the abdominal aorta, whereas the left atrium, left ventricle, aortic root and aortic arch remained free of contrast. In 2 patients in whom an aneurysm of the sinus of Valsalva ruptured into the right ventricle, the "negative" contrast effect permitted localization of the shunt. In 2 patients with transposition of the great arteries, an intact ventricular septum and a Senning operation, the intracardiac flow pattern was clearly demonstrated. No complication was observed. We conclude that pure carbon dioxide directly injected into a peripheral vein is a safe and advantageous echocardiographic contrast material. Because of its greater diffusibility in comparison with oxygen and fluid contrast media, small venoarterial shunting can be detected in defects such as atrial septal defect, ventricular septal defect and patent ductus arteriosus, in which only an arteriovenous shunt can be demonstrated by oximetry.