Undetectable High Sensitivity Cardiac Troponin T Level in the Emergency Department and Risk of Myocardial Infarction

Study Questions:

What is the negative predictive value of undetectable high-sensitivity cardiac troponin T (hs-cTnT) level and no signs of ischemia on electrocardiogram (ECG) in the emergency department (ED) for the risk of myocardial infarction (MI)?

Methods:

All patients who sought medical attention for chest pain, and had at least one hs-cTnT analyzed during 2 years at the Karolinska University Hospital, Stockholm, Sweden, were included. The investigators calculated the negative predictive values of an undetectable hs-cTnT, and ECG without ischemia, for MI and death within 30 days. Cox proportional hazards model was used to calculate hazard ratio (HR) and 95% confidence interval (CI) for the potential association between the exposure not admitted (reference admitted) and the outcome time to death adjusted for age, sex, diabetes mellitus, prior MI, and estimated glomerular filtration rate.

Results:

The authors included 14,636 patients, of whom 8,907 (61%) had an initial hs-cTnT of <5 ng/L, 21% had 5-14 ng/L, and 18% had >14 ng/L. During 30 days of follow-up, 39 (0.44%) patients with undetectable hs-cTnT had an MI, of whom 15 (0.17%) had no ischemic ECG changes. The negative predictive value for MI within 30 days in patients with undetectable hs-cTnT and no ischemic ECG changes was 99.8% (95% CI, 99.7-99.9). The negative predictive value for death was 100% (95% CI, 99.9-100).

Conclusions:

The authors concluded that all patients with chest pain who have an initial hs-cTnT level of <5 ng/L and no signs of ischemia on ECG can be safely discharged directly from the ED.

Perspective:

This study reports that a first hs-cTnT level of <5 ng/L combined with no signs of ischemia on ECG had a 99.8% negative predictive value for MI and a 100% negative predictive value for death within 30 days. The authors argued that such patients can be safely discharged directly from the ED. As chest pain is one of the most common symptoms in patients seeking medical attention in the ED, this strategy may help to reduce overcrowding of the ED.

Keywords: Myocardial Infarction, Follow-Up Studies, Proportional Hazards Models, Sweden, Biological Markers, Chest Pain, Troponin T, Glomerular Filtration Rate, Emergency Service, Hospital, Confidence Intervals, Electrocardiography, Diabetes Mellitus, ACC Annual Scientific Session


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