Assessment of the intracardiac left to right shunts with a single scintillation probe

In order to assess the accuracy of pulmonary time-activity curves obtained at bedside with a single scintillation probe and Technetium-99m-labelled erythrocytes, pulmonary to systemic flow ratio (Qp:Qs) was calculated for radionuclide and hemodynamic investigations in 104 patients with suspected intracardiac left to right shunts. Cardiac catheterization confirmed the presence of shunts in 76 patients. Pulmonary time-activity curve was 100% sensitive, 88% specific, and 96% accurate in detecting the shunt. Correlation between the radionuclide and hemodynamic Qp:Qs was excellent (r=0.93). Results were classified in four quantitative categories according to the Qp:Qs values. In 76 patients (73%) radionuclide and hemodynamic data fell in the same category. We conclude that radionuclide pulmonary time-activity curves generated with a scintillation probe is a reliable method in quantitative assessment of intracardiac left to right shunts.