Assessment of post-infarction jeopardized myocardium by vasodilation--thallium-201 tomography: impact on risk stratification.

For the purpose of risk stratification 80 consecutive patients (mean age 58 ± 7 years) with a chest pain syndrome after documented myocardial infarction underwent tomographic vasodilation-redistribution thallium-201 perfusion imaging, using 0.56 mg kg−1 intravenous dipyridamole. Tomograms were analysed for size and location of reversible and fixed perfusion defects and correlated to angiographic characteristics, left ventricular ejection fraction and wall motion, collateral status and 1-year prognosis, as measured by cardiac events within 12 months. No serious side-effects were noted with the diagnostic use of intravenous dipyridamole. According to the perfusion pattern three subgroups of post-infarction patients were identified: (1) by ischaemia at a distance with redistribution in non-infarct related territories (n = 48); (2) by peri-infarctional ischaemia with redistribution in the territory of the ‘infarct artery’ (n = 9); and (3) by exclusively fixed defects without redistribution (n = 23). Ischaemia at a distance was associated with a larger reversible defect than peri-infarctional ischaemia (P<0.05) and the pattern without redistribution (P<0.005); the fixed defect size, however, was similar in all three subgroups. In addition, the severity of coronary artery disease (Gensini score and number of diseased vessels) and the degree of collateralization was higher in the presence of a redistribution pattern (P<0.05), although no significant differences in global and regional function were noted as a function of thallium-201 redistribution. By cumulative proportional analysis, patients with distant ischaemia were characterized by an annual cardiac event rate of 96% vs a 66% in patients with peri-infarctional ischaemia (P<0.05) and 39% in patients without an ischaemic reaction (P<0.01). Thus, tomographic vasodilation-redistibution Tl-201 imaging is safe in post-infarction patients, allows the quantitative assessment of fixed and reversible perfusion defects and provides a useful risk stratification with prognostic potential for cardiac events.