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

We observed increased lung thallium-201 (²⁰¹Tl) activity on initial stress myocardial images in patients with coronary artery disease (CAD). To assess the clinical significance of this finding, initial and 2-hour delayed ²⁰¹Tl 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 ²⁰¹Tl activity was expressed as a percentage of maximal myocardial ²⁰¹Tl activity per picture element (lung ²⁰¹Tl index) for each imaging time. The lung ²⁰¹Tl 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 ²⁰¹Tl stress myocardial perfusion images, and (4) qualitative assessment of initial lung ²⁰¹Tl uptake after stress. In 10 control patients the mean initial lung ²⁰¹ Tl index was 37.6 ± 2.5% (± SEM). In 29 patients with two- and three-vessel CAD, the mean initial lung ²⁰¹Tl 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 ²⁰¹Tl index was 45.6 ± 3.6% (p = NS compared with controls). Patients with CAD decreased their mean lung ²⁰¹Tl index from initial to delayed images (p<0.05), but control patients did not. When a lung ²⁰¹Tl index of 54.5% (2 SD above the control mean) was chosen as abnormal, patients who had CAD and an abnormal initial lung ²⁰¹Tl index had significantly reduced resting ejection fractions (mean 58.2 ± 2.5%) compared with patients who had CAD and a normal lung ²⁰¹Tl 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 ²⁰¹Tl 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 ²⁰¹Tl indexes determined quantitatively correlated with the quality assessment of initial lung ²⁰¹Tl uptake after stress. The finding of elevated lung ²⁰¹Tl activity on stress myocardial images correlates with increased severity of underlying coronary artery disease and left ventricular dysfunction. ²⁰¹Tl lung activity after stress can be easily quantitated.