TRAPID-AMI Published: Early Diagnosis of Acute MI Ruled Out Within 1 Hour Using High-Sensitivity Troponin

In patients presenting with chest pain, a high-sensitivity cardiac troponin T (hs-cTnT) algorithm is effective at both diagnosing acute MI and ruling it out within 1 hour, according to a study published online January 12, 2016, in the Annals of Emergency Medicine. The study also found that mortality rates remained very low over the 1-year follow-up period for patients in whom the strategy had ruled out acute MI. 

“We found that accurate rule-out and rule-in seems to be feasible much more rapidly than suggested in current American Heart Association/American College of Cardiology guidelines in the majority of patients,” write Christian Mueller, MD, of University Hospital Basel (Basel, Switzerland), and colleagues.

The international, multicenter TRAPID-AMIstudy, first presented at the European Society of Cardiology congress in 2014, was conducted at 12 centers in the United States, Europe, and Australia. From August 2011 to June 2013, investigators enrolled 1,282 consecutive patients (mean age 62 years; 63% men) with chest pain suggestive of acute MI. All had symptom onset within the prior 6 hours (median 1.8 hours) and had a median time from chest pain onset to first study blood draw of 3.4 hours. Because definite interpretation of the initial ECG was not required, patients with STEMI were allowed to be enrolled.

The purpose of TRAPID-AMI was to externally validate the diagnostic accuracy of a 1-hour algorithm that had previously been tested in the APACE trial, which was conducted in European patients only, allowed a presentation time of up to 12 hours and excluded STEMI patients. That study showed a negative predictive value of 100% for ruling out MI and a positive predictive value of 76% for diagnosing MI.

The algorithm categorizes patients into 3 groups depending on baseline troponin and changes over 1 hour, as measured by the hs-cTnT assay:

• Rule-out zone: MI is ruled out if the level is < 12 ng/L at baseline and increases by < 3 ng/L
• Rule-in zone: MI is diagnosed if the level is ≥ 52 ng/L at baseline or increases by ≥ 5 ng/
• Observational zone

High Accuracy, Low Mortality

Overall, 63.4% of patients had acute MI ruled out, 14.4% were diagnosed with MI, and 22.2% were placed in the observational zone. The negative predictive value and sensitivity were 99.1% and 96.7%, respectively, for acute MI in the rule-out zone, with a miss rate of 0.9%. All missed adjudicated acute MIs were small, and most patients with them received a clinical discharge diagnosis of unstable angina.

Positive predictive value and specificity were 77.2% and 96.1%, respectively, for acute MI in the rule-in zone. The most common other diagnoses in the rule-in zone were myocarditis, unstable angina, takotsubo cardiomyopathy, heart failure, arrhythmia, and symptoms of unknown origin. Among patients placed in the observational zone, 22.5% had an adjudicated diagnosis of acute MI.

The area under the receiver operating characteristics curve (AUC) for the combination of hs-cTnT at presentation with 1-hour levels and 1-hour absolute change (0.95; 95% CI 0.93-0.97) was higher than the AUC of hs-cTnT alone at presentation (0.91; 95% CI 0.88-0.93) and comparable to the combination of hs-cTnT at presentation with 2-hour levels and 2-hour absolute change (0.95; 95% CI 0.93-0.96).

The findings were consistent across subgroups defined by sex, age, presence of CAD, and whether patients presented within 3 hours of chest pain onset.

Cumulative 30-day mortality was 0.1%, 2.7%, and 0.7%, in the rule-out, rule-in, and observational zones, respectively, and continued in a similar pattern out to 365 days of follow up.

Support for 1-Hour Algorithm

“Overall, the hs-cTnT 0-hour/1-hour algorithm assigned 78% of patients a definite process (either rule-out or rule-in), with only 22% of patients remaining in the observational zone,” Mueller and colleagues write. “Thereby, the hs-cTnT 0-hour/1-hour algorithm seemed to be even more complete and more effective in the early triage of acute chest pain patients than other important emerging early triage strategies in similar study populations.”

Additionally, they say, the algorithm was superior to the interpretation using a single cutoff value of 14 ng/L for hs-cTnT, both with regard to negative and positive predictive value. “This documents the superiority of the 0-hour/1-hour algorithm versus the use of a single measurement of hs-cTnT for both ruling out and ruling in acute myocardial infarction,” Mueller and colleagues observe.

They also note that the diagnostic accuracy of the combination of hs-cTnT at presentation and 1-hour change was higher than the presentation value only and comparable to the combination of hs-cTnT at presentation and 2-hour change, providing further support for the selection of the 1-hour time point for the second measurement of hs-cTnT. “One hour seems to be an excellent compromise between speed and accuracy when using hs-cTnT,” Mueller and colleagues say.

However, they caution that assessing patients with acute chest pain in the ED is not limited to the rule-out or rule-in of acute MI. “Although unstable angina has recently been shown to be a less serious disorder, with no benefit from routine early revascularization or aggressive antiplatelet therapy compared with acute myocardial infarction, many patients who experience it may still benefit from hospitalization,” the researchers conclude.

Source:
Mueller C, Giannitsis E, Christ M, et al. Multicenter evaluation of a 0-hour/1-hour algorithm in the diagnosis of myocardial infarction with high-sensitivity cardiac troponin T. Ann Emerg Med. 2016;Epub ahead of print.

Disclosures:

• Mueller reports research support from Abbott, Alere, AstraZeneca, Beckman Coulter, BRAHMS, Critical Diagnostics, Roche, Siemens, Singulex, and Sphingotec; and speaker and consulting honoraria or travel support from Abbott, Alere, AstraZeneca, Bayer, BG       Medicine, bioMérieux, BRAHMS, Cardiorentis, Daiichi Sankyo, Eli Lilly, MSD, Novartis, Radiometer, Roche, Siemens, and Singulex.

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