Single High-Sensitivity Cardiac Troponin T Measurement Could Rule Out Acute Myocardial Infarction

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Researchers do not recommend this approach within 3 hours of symptom onset because troponin may not be yet be detectable.
Researchers do not recommend this approach within 3 hours of symptom onset because troponin may not be yet be detectable.

A collaborative meta-analysis published in the Annals of Internal Medicine demonstrated that a single measure of high-sensitivity cardiac troponin T (hs-cTnT) may successfully rule out acute myocardial infarction (AMI) in certain patients who visit emergency departments (ED) with potential symptoms.1

To identify the 80% to 90% of patients presenting to EDs with chest pain who are not ultimately diagnosed with AMI, certain hs-cTnT cutoff levels have been suggested.2 Earlier findings show that AMI may be ruled out by a single hs-cTnT measurement below the limit of detection (LOD).3,4

However, because some of the limited evidence supporting these cutoffs is marked by methodological flaws and varying hs-cTnT thresholds, these results cannot be pooled to adequately assess such a strategy. If findings regarding this approach were validated, it "could enable safe discharge of many more patients than in current practice," the current researchers wrote.

To that end, the researchers conducted a meta-analysis of 11 cohort studies without the previous limitations and contacted the lead investigators for additional information required for analysis. They aimed to evaluate the effectiveness of a single hs-cTnT measurement below the LoD (<0.005 µg/L) combined with a nonischemic electrocardiogram to safely identify patients with a low AMI risk on presentation to the ED with chest pain.

Index admission AMI per Global Task Force guidelines served as the primary end point,5 with the secondary end points being death and the occurrence of a major adverse cardiac event (MACE) within 30 days after initial presentation.

The combined studies included a total of 9241 patients. Of the 30.6% of patients classified as low risk, 0.5% had AMI. Sensitivity of the AMI risk classification ranged from 87.5% to 100%, and the pooled sensitivity estimate was 98.7% (95% CI, 96.6%-99.5%). As for the secondary end points, none of the low-risk patients died during the study periods, and sensitivity for MACEs ranged from 87.9% to 100%, with a pooled sensitivity of 98.0% (CI, 94.7%-99.3%).

Overall, these findings indicate that AMI may be ruled out after 1 blood draw in a significant number of cases, although the researchers do not recommend this approach in patients presenting to the ED within 3 hours of symptom onset because troponin may not be yet be detectable.

"Moreover, because the strategy had considerable heterogeneity of sensitivity among sites, it should not be used without careful additional clinical assessment to identify patients with a high likelihood of underlying critical coronary stenosis [or without local] audits to ensure safety and efficacy," they cautioned.

Disclosures: Numerous authors disclosed grants and consulting fees from various companies and organizations, as detailed online

References

1. Pickering JW, Than MP, Cullen L, et al. Rapid rule-out of acute myocardial infarction with a single high-sensitivity cardiac troponin t measurement below the limit of detection: a collaborative meta-analysis [published online April 18, 2017]. Ann Intern Med. doi:10.7326/M16-2562

2. Six AJ, Backus BE, Kelder JC. Chest pain in the emergency room: value of the HEART score. Neth Heart J. 2008;16:191-196.

3. Body R, Carley S, McDowell G, et al. Rapid exclusion of acute myocardial infarction in patients with undetectable troponin using a high-sensitivity assay. J Am Coll Cardiol. 2011;58(13):1332-1339. doi:10.1016/j.jacc.2011.06.026

4. Rubini Giménez M, Hoeller R, Reichlin T, et al. Rapid rule out of acute myocardial infarction using undetectable levels of high-sensitivity cardiac troponin. Int J Cardiol. 2013;168(4):3896-3901. doi:10.1016/j.ijcard.2013.06.049

5. Thygesen K, Alpert JS, White HD, et al; Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Universal definition of myocardial infarction. Circulation. 2007;116(22):2634-2653. doi:10.1161/CIRCULATIONAHA.107.187397

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