Prognostic Implications of Normal Exercise Thallium Images

Abstract

Previously we observed less than 1 % event rate in patients with normal exercise thallium-201 images at a mean follow-up of 14 months. This study extends these observations over a longer follow-up period of 12-48 months (mean 27). There were 250 men and 269 women, aged 52 ±11 years (mean ± SD) of whom 64% had either typical or atypical angina pectoris. During symptom-limited exercise testing (Bruce protocol), 79 patients ( 15 %) had positive, 253 patients (49%) had negative, and the remaining patients (36%) had nondiagnostic exercise electrocardiograms. There were 255 patients (49%) who did not complete stage II of Bruce protocol. All patients had normal exercise thallium images by qualitative and quantitative analysis. During the follow-up period, there were 6 events; 2 cardiac deaths and 4 nonfatal acute myocardial infarcts occurring at 6, 12, 12, 14, 27, and 34 months after exercise testing. None of the 6 patients had positive exercise electrocardiograms and 5 patients completed stage II. All patients with events were men (2 with typical, 2 with atypical and 2 with nonanginal chest pains) giving an event rate of 0 %/year in women and 1 %/year in men. Thus, normal exercise thallium images identify a subgroup of patients at a very low risk for future cardiac events for up to 4 years irrespective of presenting symptoms, exercise tolerance and exercise electrocardiographic response. Women with normal images are particularly at a low risk.