Exercise and redistribution thallium-201 myocardial scintigraphy: changes in distribution qualitatively unaffected by previous infarction.

Eighteen patients with stable exertional angina pectoris were investigated by thallium-201 (201Tl) exercise and redistribution single photon emission computed tomography (SPECT) after coronary angiography. Eight of the patients had a previous myocardial infarct. Six patients had single-, eight double- and four triple-vessel disease. An exercise SPECT was acquired 10 min after the administration of isotope, injected 1-2 min before the termination of a symptom-limited exercise test. A redistribution SPECT was recorded 3 h later. 201Tl activity per pixel was compared between the exercise and redistribution SPECT in relative and absolute terms. For each patient there was a good correlation between activity per pixel in the redistribution SPECT and the corresponding pixels in the exercise SPECT (mean correlation coefficient 0.86 +/- 0.08), irrespective of the extent of coronary artery disease or presence of a previous infarction in the pixel region. Relative wash-out correlated to the degree of coronary artery stenosis (r = 0.48), but did not differ between infarcted and non-infarcted myocardial regions. A similar relationship was documented for pixels with visual 'refill' in the redistribution SPECT. This implies that most of the information in the redistribution SPECT was present already in the exercise SPECT. Thus, qualitative information of a similar kind is obtained from images acquired immediately after exercise and after 3-4 h of redistribution.