[Effect of body loading on the specific blood radioactivity following 99mTc in-vivo erythrocyte labelling. The effects on determining end-diastolic volume in equilibrium radionuclide ventriculography].

In 40 patients who underwent stress-equilibrium-radionuclide-ventriculography, we examined the stress-induced change of blood radioactivity concentration. A significant (p less than 0.025) increase of blood radioactivity concentration after peak exercise (mean +7.2%) was found. This increase was the result of a significant (p less than 0.025) increase of the hematocrit (mean +4.7%) due to a decrease of the plasma volume. The changes of radioactivity concentration and hematocrit neither show any correlation with peak exercise value, integral exercise or duration of exercise, nor with the increase of heart rate or blood pressure. The increase of end-diastolic volume appears to result largely from a stress-induced increase of blood radioactivity concentration. Thus, radioactivity concentration should be measured before and after exercise when evaluating volume changes caused by stress-equilibrium-radionuclide-ventriculography.