Prognostic value of exercise thallium-201 imaging performed within 2 years of coronary artery bypass graft surgery

Objectives. We sought to determine the prognostic capabilities of exercise thallium (TI)-201 tomographic imaging performed relatively early (within 2 years) after coronary artery bypass graft surgery (CABG). Background. Exercise testing is commonly performed after CABG, but few data exist demonstrating its prognostic value in this setting. Methods. Four hundred eleven patients were followed up for a median duration of 5.8 years. Eleven prospectively chosen clinical, exercise and TI-201 variables were tested for their associations with outcome end points by means of proportional hazards regression models. Results. During follow-up there were 60 deaths from any cause, 53 initial cardiac deaths or nonfatal myocardial infarctions (MIs) and 22 late (>3 months after the TI-201 study) revascularization procedures. The number of abnormal TI-201 segments on the postexercise image was the only variable in the multivariate analyses to show a significant association with all three outcome end points: chi-square 7.3, p = 0.007 for overall mortality; chi-square 8.1, p = 0.004 for cardiac death or MI; chi-square 7.8, p = 0.005 for any cardiac event. Other independent predictors of outcome were exercise duration (chi-square 10.7, p = 0.001) and age (chi-square 3.9, p = 0.049) for overall mortality and exercise angina score (chi-square 8.7, p = 0.003) for cardiac death or MI. The 5-year survival rate free of cardiac death or MI was 93% for patients without angina and a normal image or small postexercise perfusion defect versus 71% for patients with angina and a medium or large defect. Conclusions. Exercise TI- 201 imaging performed within 2 years of CABG can stratify patients into low and high risk subgroups.