Prognosis of patients with an isolated fixed thallium-201 defect and no prior myocardial infarction

Abstract

Traditionally, fixed defects in thallium-201 myocardial perfusion imaging studies have been thought to indicate the presence of scarring or myocardial infarction. 1 More recently, several investigators challenged this dogma, showing that some defects that appear fixed on standard 2- to 4-hour delayed redistribution images will show at least some reversibility if reimaged at 24 to 72 hours, 2,3 or if thallium-201 is reinjected at rest before repeat imaging, 4 and thus do not appear to represent infarction. Many prior studies found that redistribution on standard stress 2- to 4-hour delayed thallium-201 imaging has a strong predictive value for future cardiac events. However, whereas some reports have found fixed defects to have important prognostic value, 5–7 most have not. 8–21 The prognostic implications of the subgroup of fixed defects on standard imaging, which show reversibility only with reinjection or 24- to 72-hour imaging, are unknown. Therefore, it is problematic whether to treat patients with these defects the same as for standard redistribution. To provide some insight into this dilemma, we examined the outcome of 100 patients without prior myocardial infarction who had isolated fixed defects on standard exercise 2- to 4-hour redistribution thallium-201 imaging. These patients represent a cohort very likely to show reversibility with reinjection or 24- to 72-hour late imaging, because the fixed defects in these cases do not represent scarring.