The writing committee considered the following specific definitions and assumptions in the development of the consensus recommendations:

• Hs-cTn assays
• Clinical decision pathways (CDPs)
• Efficacy (the proportion of individuals meeting “rule-out” criteria based on the CDP algorithm)
• Limit of blank (the highest apparent cTn concentration found with a given assay when testing replicates of a sample known to contain no cTn, which is also known as a blank sample)
• Limit of detection (the lowest cTn concentration that can be reliably differentiated from the limit of blank when testing replicates of samples known to contain cTn)
• Limit of quantification (the lowest cTn concentration that can be reported reliably as a number)
• Minimally elevated hs-cTn or minor elevations in hs-cTn
• Elevated hs-cTn (hs-cTn values above the 99th percentile)
• Relative change in hs-cTn (percentage change in hs-cTn across serial measurements)
• Absolute change in hs-cTn
• Nonischemic electrocardiogram (ECG)

The Expert Consensus Decision Pathway is intended to parallel the usual course of assessment of patients in the ED with symptoms that require evaluation for possible acute coronary syndrome (ACS). The first step involves careful assessment of the ECG. Patients with nonischemic ECG can enter an accelerated CDP that is designed to provide rapid risk evaluation and exclusion of ACS. All patients who are classified as low risk with the use of hs-cTn-based CDPs supported by this document can generally be discharged directly from the ED without receiving any additional testing; however, outpatient testing may be considered in certain individuals.

In contrast, patients with substantially elevated initial hs-cTn values or those with significant dynamic changes over 1 to 3 hours are assigned to the abnormal/high-risk category. These individuals should be further classified according to the Universal Definition of Myocardial Infarction (MI) into type 1 or type 2 MI, or acute or chronic nonischemic cardiac injury. High-risk patients should be admitted to an inpatient facility for additional evaluation and treatment.

The initial clinical assessment of a patient with acute chest pain should focus on the rapid identification and treatment of those with life-threatening conditions, including ACS, aortic dissection, and pulmonary embolism. Those patients who are hemodynamically unstable, have significant arrhythmia, or have evidence of significant heart failure, however, should be evaluated and treated appropriately; they are not considered to be candidates for an accelerated CDP.

Disadvantages of these protocols include algorithm complexity, sensitivity to timing of blood draws, and the relegation of approximately one-fourth of patients to an observation zone in which limited evidence is available to guide subsequent assessment and treatment. An additional limitation of these algorithms is the fact that they may be susceptible to missing MIs among late presenters who are on a flat portion of a descending cTn trend, in which little or no change may be evident over 1 to 2 hours.

“This evaluation includes careful ECG review and, for appropriate patients, entry into a CDP that combines hs-cTn measurements with risk assessment and selective use of noninvasive testing,” the study authors wrote. “The CDP is used to help to guide triage, treatment, and disposition decisions. The CDP should be viewed as a tool to augment rather than replace the clinical judgment of the care team.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.