Limited usefulness of exercise testing and thallium scintigraphy in evaluation of ambulator patients several months after recovery from an acute coronary event: Implications for management of stable coronary heart disease

Objectives. This study evaluated the value of noninvasive testing to predict cardiac events in patients with stable coronary disease after hospital admission (and risk stratification) for an acute coronary event. Background. Exercise testing with thallium perfusion imaging identifies patients with obstructive coronary artery disease and has been used to stratify patients after myocardial infarction. Its usefulness for predicting cardiac events in patients with stable coronary disease after recovery from an acute coronary event was explored. Methods. Nine hundred thirty-six patients were enrolled 1 to 6 months after hospital admission for a coronary event Patients underwent exercise treadmill testing with planar thallium-201 scintigraphy and were followed up for an average of 23 months (range 6 to 43). End points were 1) unstable angina requiring hospital admission, nonfatal myocardial infarction or cardiac death; 2) nonfatal infarction or cardiac death; or 3) cardiac death alone. Results. Twelve patients died of cardiac causes (1.2%); 32 had a nonfatal myocardial infarction (3.4%); and 79 patients (8.4%) developed unstable angina in the first year. Exercise testing improved proportional hazards models constructed from clinical variables for all three end points (p < 0.05). The perfusion scan further improved models for the end points (nonfatal infarction or cardiac death and cardiac death alone, p < 0.05). However, the exercise test with or without thallium added little to the overall prediction of primary events (area under the receiver operating curve increased from 0.649 to 0,663), and only 2% to 13% of patients with abnormal results either had a nonfatal infarction or died. Conclusions. Thallium-201 scintigraphy and exercise testing variables identify patients at risk for subsequent cardiac events. However, the poor predictive performance of these tests in this group of patients with stable coronary disease severely limits their usefulness. These results suggest a limited role for exercise and thallium testing in predicting cardiac events in patients with known coronary disease.