Radionuclide quantitation of left-to-right cardiac shunts in children.

In order to evaluate the clinical usefulness of radionuclide methods measuring the magnitude of left-to-right cardiac shunts, a comparison has been made of the results obtained using these procedures with those estimated by cardiac catheterization. Seventy children in whom the presence or absence of a shunt had been established, were studied. Two methods for radionuclide shunt quantitation, the pulmonary to systemic blood flow ratio (Qp/Qs) of Maltz and Treves and their modified C2/C1, were evaluated. The former was found to be superior and showed a high correlation of shunt size with the catheter results. With attention to the performance of the investigation and in the data analysis, good discrimination can be achieved between normal patients and those with shunts. Because of the atraumatic nature of the investigation, it is concluded that the procedure is of value in the diagnosis of a cardiac murmur, the assessment of postoperative patients and the follow-up of patients known to have a small shunt.