Can We Exclude the Diagnosis of Non-ST Segment Myocardial Infarction on the Basis of a Single Troponin I and a Symptom Duration ≥8 Hours?

Abstract EN

Background.

The use of a single troponin measurement to exclude the diagnosis of non-ST segment myocardial infarction (NSTEMI) in patients that present with ischemic symptom duration ≥8 hours is sometimes used in the Emergency Department.

Study Objective.

To describe the characteristics of patients with initial nondiagnostic troponin values who develop a positive troponin while in the Emergency Department and to evaluate whether NSTEMI can be excluded using symptom duration ≥8 hours and initial troponin I.

Methods.

Retrospective chart review of patients evaluated for NSTEMI in the Emergency Department.

Results.

4,510 patients had at least two troponin I values obtained during the two-year study period.

115 (2.5%) of these patients had an initially nondiagnostic (<0.6 ng/mL) and subsequent positive (≥0.6 ng/mL) troponin I result.

Twenty-five (22%) of the 115 had duration of symptoms ≥8 hours.

Of these 25 patients, 18 had an intermediate first troponin value (i.e., >0.06 ng/mL, but <0.6 ng/mL).

Only two of the remaining seven patients had a final primary diagnosis of NSTEMI.

Conclusion.

The use of a negative initial troponin I together with a symptom onset of ≥8 hours defines a population with a very low incidence of a hospital diagnosis of NSTEMI.