Significant Residual Ischemia on Myocardial Perfusion Imaging after Optimal Medical Therapy with or without Coronary Revascularization Predicts a Worse Prognosis

Background : Myocardial perfusion imaging (MPI) by single photon emission computed tomography is widely performed in patients with coronary artery disease (CAD). These days, the relation between MPI findings and the prognosis of CAD has been reported. Methods : A total of 188 consecutive patients with stable CAD were retrospectively enrolled. They all had ischemic findings in the initial stress/resting MPI and underwent a repeat stress/resting MPI within one year of the initial test. We evaluated the summed stress score, summed rest score, and summed difference score (SDS). We defined %residual ischemia as the percent SDS on repeat MPI relative to that on initial MPI (post SDS × 100/pre SDS). We followed the patients until occurrence of an adverse event or for at least one year after repeat MPI to assess adverse events including cardiac death, nonfatal myocardial infarction, hospitalization for heart failure, revascularization by percutaneous coronary intervention or coronary artery bypass grafting, stroke, and non-cardiac death. Results : Fifty-four patients (28.7%) experienced adverse events. According to multivariate Cox proportional hazards regression analysis of adverse event rates, more extensive %residual ischemia was associated with a higher incidence of adverse events (HR 1.025, p = 0.018). According to Kaplan-Meier analysis, patients with significant %residual ischemia had a higher risk of adverse events than those with mild %residual ischemia (p = 0.001, log rank test). Conclusion : In patients with CAD, significant residual ischemia on repeat MPI may predict a worse prognosis for CAD patients receiving optimal medical therapy with or without coronary revascularization.