Contrast echocardiography: transmission of echoes to the left heart across the pulmonary vascular bed

All available reports indicate that the echoproducing quality of agents used for contrast echocardiography is lost during their passage through the pulmonary or systemic capillary bed. A technique has been developed to transmit echoes to the left heart across the pulmonary vascular bed with the use of venous catheterization. In 43 patients with acquired or congenital heart disease, a balloon-tipped catheter was wedged in a pulmonary arterial branch, the balloon was inflated, then rapidly deflated after injection of an echoproducing substance, while M-Mode or two-dimensional echocardiograms were recorded. Echoes consistently appeared in the left heart following injection of indocyanine green (5–10 mg), saline (5 ml) or CO2 (0.5–1 ml). In 25 patients with a documented left-to-right shunt, echoes also appeared in the right heart chamber receiving the shunt. There were no false negatives nor false positives. No complications or side effects were observed. The presumed mechanism of transmission is the achievement of a high concentration of echoes and/or bypassing of pulmonary capillaries through physiological intrapidmonary shunts. The method is proposed as a screening procedure to be used during right heart catheterization so as to avoid, if possible, the injection ofradioopaque contrast and the invasion of the left heart