Prognostic implications of normal exercise thallium-201 images

The usefulness of exercise-thallium-201 imaging (ETI) in the evaluation of patients (pts) with suspected coronary heart disease (CHD) is well established. A more far-reaching use of the method is, however, in risk stratification. The purpose of this study was to determine the prognosis of pts with normal ETI results. The study group consisted of 432 pts (218 men and 214 women with a mean age of 51 years) who underwent ETI for suspected CHD. Of those, 305 (71%) had typical or atypical angina pectoris and 65% achieved ≥85% of maximum predicted heart rate. The exercise ECG was positive in 65 pts (15%), inconclusive in 153 (35%) and negative in 214 (50%). At a mean follow-up of 13.5 mos (range 4 to 44), 6 pts had cardiac events: 1 had fatal myocardial infarction (MI) and 5 had non-fatal MI's, (one pt with non-fatal MI had spasm by coronary angiography). Two other pts had coronary artery bypass grafting. Of the 6 pts with events, none had positive exercise ECG's, 2 had typical angina, 2 had atypical angina, and 2 had non-anginal chest pain. The authors conclude the following: (1) normal ETI results identify pts at a very low risk for future cardiac events (death: 0.2%, MI: 1.2%) which is comparable to that reported in pts with chest pain and angiographically normal coronary angiograms, (2) pts with positive exercise ECG's but normal ETI results have good prognosis, none of the 65 pts in this study had cardiac events, and, (3) ETI is a far better prognostic indicator than exercise ECG, because of the high incidence of inconclusive exercise ECG results (35%) and the good prognosis in pts with positive results