Two-Hour Algorithm for Triage toward Rule-Out and Rule-In of Acute Myocardial Infarction by Use of High-Sensitivity Cardiac Troponin I.

BACKGROUND: The early triage of patients toward rule-out and rule-in of acute myocardial infarction (AMI) is challenging. Therefore, we aimed to develop a 2-h algorithm that uses high-sensitivity cardiac troponin I (hs-cTnI). METHODS: We prospectively enrolled 1435 (derivation cohort) and 1194 (external validation cohort) patients presenting with suspected AMI to the emergency department. The final diagnosis was adjudicated by 2 independent cardiologists. hs-cTnI was measured at presentation and after 2 h in a blinded fashion. We derived and validated a diagnostic algorithm incorporating hs-cTnI values at presentation and absolute changes within the first 2 h. RESULTS: AMI was the final diagnosis in 17% of patients in the derivation and 13% in the validation cohort. The 2-h algorithm developed in the derivation cohort classified 56% of patients as rule-out, 17% as rule-in, and 27% as observation. Resulting diagnostic sensitivity and negative predictive value (NPV) were 99.2% and 99.8% for rule-out; specificity and positive predictive value (PPV) were 95.2% and 75.8% for rule-in. Applying the 2-h algorithm in the external validation cohort, 60% of patients were classified as rule-out, 13% as rule-in, and 27% as observation. Diagnostic sensitivity and NPV were 98.7% and 99.7% for rule-out; specificity and PPV were 97.4% and 82.2% for rule-in. Thirty-day survival was 100% for rule-out patients in both cohorts. CONCLUSIONS: A simple algorithm incorporating hs-cTnI baseline values and absolute 2-h changes allowed a triage toward safe rule-out or accurate rule-in of AMI in the majority of patients.

Accelerated diagnostic protocol using high-sensitivity cardiac troponin T in acute chest pain patients.

BACKGROUND: We aimed to evaluate the efficacy and safety of using high-sensitivity cardiac troponin T (hs-cTnT) within an accelerated diagnostic protocol (ADP) in patients presenting with symptoms suggestive of acute myocardial infarction (AMI) for rapid rule-out of AMI. METHODS: In two independent large multicenter studies, levels of hs-cTnT at presentation and at 2 h were combined with the Thrombolysis In Myocardial Infarction (TIMI) risk score and ECG findings. The ADP defined patients with normal levels of hs-cTnT at presentation and 2 h, a TIMI score ≤1, and normal ECG findings as candidates for rapid rule-out of AMI and rapid discharge. Major adverse cardiac events (MACEs) occurring within 30-days were centrally adjudicated by two independent cardiologists. RESULTS: In the derivation cohort, among 1085 consecutive patients 198 patients (18.2%) had a MACE. The ADP classified 374 patients (34.5%) as low-risk. None of these patients had a MACE at 30 days, resulting in a negative predictive value (NPV) of 100% (95% CI, 99.0-100%) and a sensitivity of 100% (95% CI, 98.2%-100%). In the validation cohort, among 1590 consecutive patients 231 patients (14.5%) had a MACE. The ADP classified 641 patients (40.3%) as low-risk. 6 of these patients had a MACE at 30 days, resulting in a NPV of 99.1% (95% CI, 98.0-99.6%) and a sensitivity of 97.4% (95% CI, 94.5-98.8%). CONCLUSIONS: The ADP including hs-cTnT allows early identification 35 to 40% of patients to be at extremely low risk of MACE and therefore ideal candidates for outpatient management.