One hundred seven asymptomatic patients who underwent intravenous
dipyridamole thallium imaging were evaluated to determine prognostic indicators of subsequent
cardiac events over an average follow-up period of 14 +/- 10 months. Univariate analysis of 18 clinical, scintigraphic and angiographic variables revealed that a reversible
thallium defect, a combined fixed and reversible
thallium defect, number of segmental
thallium defects and extent of
coronary artery disease were significant predictors of subsequent
cardiac events. Of the 13 patients who died or had a nonfatal
infarction, 12 had a reversible
thallium defect. Stepwise logistic regression analysis selected a reversible
thallium defect as the only significant predictor of
cardiac events. When death or
myocardial infarction was the outcome variable, a combined fixed and reversible
thallium defect was the only predictor of outcome. In patients without previous
myocardial infarction, the
cardiac event rate was significantly greater in those with an abnormal versus normal
thallium scan (55% versus 12%, p less than 0.001). Thus, intravenous
dipyridamole thallium scintigraphy is a useful noninvasive test to risk stratify asymptomatic patients with
coronary artery disease. A reversible
thallium defect most likely indicates silent
myocardial ischemia in a sizable fraction of patients in this clinical subset and is associated with an unfavorable prognosis.