Background: We evaluated the prognostic value of exercise 201Tl indexes of myocardial hypoperfusion in patients with suspected or known coronary artery disease.
Methods and results: Patients were divided into two groups: group I consisted of 332 patients with diagnostic electrocardiographic stress test results and group II consisted of 144 patients with nondiagnostic (inadequate or uninterpretable) stress electrocardiograms. At the 2-year follow-up, 20 hard events (16 cardiac deaths and 4 nonfatal myocardial infarctions) and 80 soft events (coronary revascularization procedures) occurred in group I. Considering total events, thallium imaging provided significant prognostic information in addition to clinical and exercise stress test data in the total study population (p < 0.001) and in patients with previous myocardial infarction (p < 0.001); in patients without previous infarction, thallium imaging added incremental prognostic value only in those with positive electrocardiographic stress test results (p < 0.01). When only hard events were considered, thallium variables added further information only in patients with previous myocardial infarction (p < 0.05). In group II at the end of follow-up, 15 hard and 39 soft events had occurred. In these patients occurrence of total (p < 0.001), hard (p < 0.05), and soft (p < 0.001) events was higher in those with abnormal thallium scintigraphic results than in those without. Moreover, no clinical and exercise variable, except history of myocardial infarction, was significantly related to outcome, whereas both indexes of extent and severity of hypoperfusion were significant.
Conclusions: The results of this study demonstrate that scintigraphic indexes of myocardial hypoperfusion obtained by qualitative planar thallium imaging give unique prognostic information in patients with nondiagnostic electrocardiographic stress test results. Thallium imaging provides incremental prognostic information even in patients with diagnostic electrocardiographic stress test results but not in the low-risk subset of patients without previous infarction who have negative electrocardiographic stress test results.