Value of computer analysis of exercise thallium images in the noninvasive detection of coronary artery disease

An analysis was made of 196 patients with no previous myocardial infarction who had undergone thallium imaging with exercise and cardiac catheterization. Patients with a prior myocardial infarction were excluded, because in such situations the presence of CAD is already virtually certain. The aim was to determine the diagnostic value of computer-analyzed thallium imaging with exercise compared with the clinical and electrocardiographic assessment and analysis of visual images. To determine what variables correlated best with CAD, all were compared using stepwise analysis of logistic regression. This study provided an equation for calculating the probability of CAD. Data indicate that the major value of combining variable with statistical modeling was the optimization of specificity. The dominant variable was the number of initial quantitated defects with thallium. Clearance and redistribution were not needed in part because of the high quality of the method of quantification and in part because of selection of patients. The model permits the high sensitivity of this variable to be maintained but eliminates false-positive results in 15% of the patients with no CAD by using non-imaging variables available to the clinician (sex, peak cardiac rate, and the response of the ST segment during exercise)