Lung thallium-201 uptake after stress testing in patients with coronary artery disease.

We observed increased lung thallium-201 (201T1) activity on initial stress myocardial images in patients with coronary artery disease (CAD). To assess the clinical significance of this finding, initial and 2hour delayed 201T1 images were stored in a computer immediately after supine stress testing in 49 patients (39 with CAD and 10 controls). Regions of interest over the heart and lung were selected on the computer-generated images and quantitative lung 201T1 activity was expressed as a percentage of maximal myocardial 201T1 activity per picture element (lung 201T1 index) for each imaging time. The lung 201T1 index was then compared with (1) the extent of CAD at catheterization, (2) resting left ventricular ejection fraction by multigated blood pool scintigraphy, (3) the results of the initial 201T1 stress myocardial perfusion images, and (4) qualitative assessment of initial lung 201T1 uptake after stress. In 10 control patients the mean initial lung 20MT1 index was 37.6 + 2.5% (± SEM). In 29 patients with twoand three-vessel CAD, the mean initial lung 201T1 index was elevated, at 53.5 ± 2.2% (p < 0.001 compared with controls), while in 10 patients with one-vessel CAD, the mean initial lung 201T1 index was 45.6 ± 3.6% (p = NS compared with controls). Patients with CAD decreased their mean lung 201T1 index from initial to delayed images (p < 0.05), but control patients did not. When a lung 201T1 index of 54.5% (2 SD above the control mean) was chosen as abnormal, patients who had CAD and an abnormal initial lung 201T1 index had significantly reduced resting ejection fractions (mean 58.2 ± 2.5%) compared with patients who had CAD and a normal lung 201T1 index (mean 66.0 + 2.1%) (p < 0.05). Patients with CAD and four or five of six abnormal segments on the initial myocardial perfusion images had higher initial lung 201T1 indexes (mean 59.1 + 13.0%) compared with patients with CAD and one or no abnormal segments on the initial myocardial perfusion images (mean 44.5 ± 10.3%) (p < 0.01). Initial lung `01TI indexes determined quantitatively correlated with the qualitative assessment of initial lung 201T1 uptake after stress. The finding of elevated lung 201T1 activity on stress myocardial images correlates with increased severity of underlying coronary artery disease and left ventricular dysfunction. 201T1 lung activity after stress can be easily quantitated.