The reinjection of a small dose of thallium-201 after stress and delayed imaging often shows new redistribution in the region with persistent defect.

The purpose of this study was to determine the incidence of incomplete redistribution on conventional delayed image and to compare the left venticular wall motion abnormality with myocardial viability in patients with coronary artery disease.

We studied 12 patients with chronic coronary artery disease, using exercise thallium-201 Single Photon Emission Tomopraphy(TI-201 SPECT) and coronary angiopraphy with contrast ventriculography. Patients received 2mCi of thallium intravenously during exercise, redistribution images were performd 4 hour late and a second dose of 1mCi of thallium was injected at rest immediately there after. The three sets of image(stress, redistribution and reinjection) were analyzed. The left ventricular myocardium was divided into 7 segments and regional wall motion was scored on scale from 2(normal) to -1(dyskinesis).

1) The redistribution was obtained in 42.9% of the segments with persistent TI-202 defect on 4 hour delayed image.

2) Myocardial viability was observed in 38.9% of regions with all motion abnormality on contrast ventriculography.

3) The wall motion score was lower in the segments with persistent TI-201 defect on reinjection image than those with transient defect(p<0.05).

4) In 42.9% of the regions with wall motion abnormality on contrast ventrculography before coronary artery bypass graft, normal TI-201 image was observed after coronary artery bypass graft.

Thallium-201 reinjection image can be used to identify viable myocardium in segments that demonstrate a persistent thallium defect on conventional delayed images patients with chronic coronary artery disease and left venticular dysfuction.