Grey Zone Troponin Values and the Risk for Poor Cardiovascular Outcome Among Hospitalized Patients

Background: Grey 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 who have initial grey zone troponin will eventually have positive troponin and will be defined as having an acute coronary syndrome. We aimed to investigate the long-term outcome of patients hospitalized with chest pain and grey zone troponin elevation.

Methods: We investigated 14,433 patients hospitalized in a tertiary center with chest pain. All patients had serial measurements of troponin during hospitalization. Patients were divided into two groups based on their initial troponin levels: negative troponin (N=9,172) and grey zone troponin (N=5,261). All patients underwent myocardial perfusion imaging (MPI) as part of the initial evaluation.

Results: Mean age of the study population was 68±12, of whom 33% were women. Patients with a grey zone troponin were older, more likely to be males and with significantly more cardiovascular risk factors. Patients with grey zone troponin had a significantly higher risk of an abnormal MPI result (82% vs. 61%, p<0.001). Multivariate analysis adjusted for age, gender, cardiovascular risk factors and abnormal MPI result found that patients with grey zone troponin were 2.3 times more likely to be hospitalized within 1 year (CI 2.15-2.55, p<0.001), 2.0 times more likely to undergo revascularization (CI 1.84-2.23, p<0.001) and 3.3 times more likely to die at 1-year post index hospitalization.

Conclusions: Grey zone troponin elevation is an independent risk factor associated with adverse events and therefore patients with an initial value in this range should be closely monitored and aggressively managed.