Myocardial
thallium uptake has been assessed at the time of
thallium scanning in a group of 50 male patients undergoing coronary arteriography and 10 young healthy volunteers. The net
thallium dose injected was obtained by counting the dose prior to injection using the
gamma camera and counting the syringe and IV
cannula after injection. Significantly higher levels of myocardial
thallium uptake were obtained in both the volunteers and patients with normal coronary anatomy (1.36% +/- 0.32%, n = 10 and 0.93% +/- 0.26%, n = 9, respectively) compared to patients with single, double or triple vessel coronary artery disease (0.63% +/- 0.19%, n = 11; 0.70% +/- 0.20%, n = 15; 0.67 +/- 0.18, n = 15, respectively). Exercise tests were positive in 46% of patients with
coronary artery disease with an overall predictive accuracy of 56%.
Thallium scans were positive in 68% of patients at a specificity of 89%. If the range of myocardial
thallium uptake from the patients with normal coronary arteries is used to define a lower limit of normal, then the sensitivity of the
thallium scan with
thallium uptake is 90% with a predictive accuracy of 90% in the detection of significant
coronary artery disease in this group of patients. Thus, estimation of total %
thallium uptake is a simple index which yields useful diagnostic clinical information.