Stress-only Tc-99m myocardial perfusion imaging in an emergency department chest pain unit

Background: Stress-only myocardial perfusion imaging (MPI) saves time by eliminating rest imaging, which is important for emergency department (ED) throughput but has not been studied in an ED population. Study Objective: To determine the prognosis of a normal stress-only MPI study compared to a normal rest-stress MPI and establish its effectiveness in an ED setting. Methods: All patients evaluated in the ED over 6.5 years who underwent a stress-only technetium-99m gated MPI were compared to those who had a rest-stress study. All-cause mortality was determined using the Social Security Death Index. Survival was analyzed in patients with normal and abnormal MPI results. Results: A total of 4145 studies (2340 stress-only, 1805 rest-stress) were performed. Patients' average age was 57.9 years, 38.5% were male, and most had an intermediate or low pretest risk of coronary artery disease (87.7%). Average follow-up was 35.9 ± 20.9 months. In patients with normal perfusion, at 1 year of follow-up there were 11 deaths in the stress-only group (0.5% 1-year mortality), and 13 deaths in the rest-stress cohort (1.1% 1-year mortality). At the end of follow-up, the stress-only group had a lower all-cause mortality (p < 0.0001) and similar risk adjusted all-cause mortality (p = 0.10) than the rest-stress cohort. Patients with abnormal perfusion demonstrated the expected differential prognosis based on total perfusion deficits in both groups. Conclusions: A normal stress-only MPI study has a benign 1-year prognosis similar to a rest-stress study when performed in the ED. The ability to triage patients more rapidly and reduce radiation exposure represents an attractive alternative for low-risk patients.