The adequacy of radioisotope mixing from bolus injections in first-pass radionuclide angiographic assessment of right ventricular function: a study using gold-195m.

The adequacy of radioisotopic mixing in first-pass radionuclide studies of right ventricular function was assessed in 27 patients using multiple injections of gold-195m (half-life 30.5 sec). A theoretical disadvantage of the first-pass technique is inadequate mixing of the injected bolus with blood prior to entry into the right ventricle. Since the calculation of ejection fraction is based on the assumption of complete mixing, this would lead to errors. In order to assess the effects of bolus injection rates and bolus duration on the calculation of right ventricular ejection fraction, multiple, rapid, sequential studies were performed using gold-195m at four bolus injection rates (10, 5, 2 and 1 ml/sec). Slowing the injection rate caused a significant increase in bolus duration, and a significant increase in the number of cardiac cycles available for analysis. Mean ejection fraction, however, was not significantly changed. There was good correlation between right ventricular ejection fraction at all injection rates when compared to 10 ml/sec, and no injection rate led to a consistent over or underestimate of right ventricular ejection fraction. There was no significant relationship between change in bolus duration and variation in ejection fraction. These data indicate that mixing is adequate for first-pass studies of right ventricular function using a rapid bolus.