Poor outcome among patients undergoing myocardial perfusion imaging with intermediate-zone troponin

Background: Intermediate zone troponin elevation is defined as one to five times the upper limit of normal. Approximately half the patients presenting with chest pain to the emergency department have initial intermediate zone troponin. Objectives: We aimed to investigate the long-term outcome of patients hospitalized with chest pain and intermediate zone troponin elevation. Methods: We investigated 8269 patients hospitalized in a tertiary center with chest pain. All patients had serial measurements of troponin during hospitalization. Patients were divided into three groups based on their initial troponin levels: negative troponin (N = 6112), intermediate zone troponin (N = 1329) and positive troponin (N = 828). All patients underwent myocardial perfusion imaging (MPI) as part of the initial evaluation. Results: Mean age of the study population was 68 ± 11, of whom 36% were women. Patients with an intermediate zone troponin were older, more likely to be males, and with significantly more cardiovascular co-morbidities. Multivariate analysis adjusted for age, gender, cardiovascular risk factors, and abnormal MPI result found that patients with intermediate zone troponin had a 70% increased risk of re-hospitalization at 1 year (HR 1.70, 95%CI 1.48–1.96, p-value < 0.001) and 5.3 times higher risk of total mortality at 1-year (HR 5.33, 95%CI 3.65–7.78, p-value < 0.001). sub-group analysis found that among the intermediate zone troponin group, patients with double intermediate zone troponin had the poorest outcome. Conclusions: Intermediate zone troponin elevation is an independent risk factor associated with adverse outcomes and therefore patients with an initial value in this range should be closely monitored and aggressively managed.