Quantitative analysis of thallium-201 uptake and the effect of heart rate

In the successive myocardial imaging by thallium-201, the uptake by myocardial cells was assessed quantitatively. At a steady hemodynamic state, the second uptake was able to be predicted from the first uptake count and the ratio of the first and the second background counts. This predicted counts showed a high correlation with the actual counts (r = 0.987, p < 0.001). No significant difference was observed in two counts. When heart rate was increased in six patients who were implanted a programmable pacemaker during the second myocardial imaging, the actual counts exceeded the predicted ones significantly (p < 0.001). An increase of the counts by 36% was observed in the average following the change of heart rate from 60 beats/min to 90 beats/min. Since the tissue level of uptake is dependent upon the blood level and the partition coefficient, this increase of myocardial uptake suggests an alteration in the partition coefficient.