Quantitative radionuclide angiocardiography for determination of chamber to chamber cardiac transit times

Abstract

A radionuclide method is described for determination of chamber to chamber cardiac transit times using only an intravenous injection. Using the Digital Autofluoroscope, counts of radioactivity from each square centimeter over the precordium were recorded onto computer tape at 0.23 second intervals after intravenous injection of 10 millicuries of 99mtechnetium pertechnetate. Computer analysis of counts grouped detector units with similar time responses into areas corresponding to discrete cardiac regions. From the resulting indicatordilution curves, appearance, peak and mean transit times were calculated for each cardiac region. Studies were obtained in 10 normal subjects, 14 patients with cardiac septal defects and left to right shunting and 20 patients with valvular stenosis or insufficiency. Among the latter patients, 8 had mitral stenosis and 8 had aortic insufficiency. Patients with a left to right shunt greater than 15 percent consistently demonstrated rapid pulmonary transit of tracer. In addition, specific abnormalities of curve configuration occurred in patients with a shunt greater than 30 percent. Transit times from the right atrium to left ventricle averaged 9.2 ± 1.2 seconds in normal subjects, 13.3 ± 2.2 seconds in patients with mitral stenosis and 14.6 ± 2.8 seconds in patients with aortic insufficiency. Pulmonary mean transit time was 6.6 ± 1.1 seconds in normal patients, 9.2 ± 1.7 seconds in those with mitral stenosis and 11.7 ± 3.1 seconds in those with aortic insufficiency. Pulmonary blood volume was 362 cc/m 2 in patients with mitral stenosis and 508 cc/m 2 in those with aortic insufficiency. These data suggest that pulmonary mean transit time was prolonged primarily by decreased cardiac output in mitral stenosis and by increased pulmonary blood volume in aortic insufficiency. The simple technique described consistently provided hemodynamic data that appear to be useful for diagnosis and management of cardiac diseases.