Coronary artery disease (CAD) is one of the leading causes of mortality in the U.S.1 One of the most common manifestations of clinically significant CAD is chest pain resulting from cardiac ischemia or myocardial infarction (MI).2 While chest pain is a common symptom of patients presenting to clinics and emergency departments, a relatively small proportion of patients presenting to the emergency department with acute chest pain are ultimately diagnosed with MI. Identification of which patients with chest pain are experiencing acute ischemic heart disease is critical since a delay in diagnosis can impede the application of effective therapies, such as thrombolytic agents or primary percutaneous coronary intervention (PCI).
Patients who present for medical attention with chest pain or other symptoms that suggest acute ischemia or infarction are often considered to have acute coronary syndrome (ACS). ACS typically serves as a “working diagnosis” for patients suspected of having ischemic heart disease, pending the establishment or ruling out of specific diagnoses.2 The first and potentially most important test typically administered in the workup of a patient with symptoms suggestive of ACS is the standard, resting 12-lead electrocardiogram (ECG). Typically, the ECG will indicate ST elevation myocardial infarction (STEMI), or it will be normal or nondiagnostic. If the ECG indicates STEMI, the patient will most likely be taken directly to coronary angiography, and clinical decisionmaking and subsequent patient outcomes would not be expected to improve with further testing. A normal or nondiagnostic ECG result does not rule out the possibility of acute ischemia or infarction, so further testing is usually indicated if the clinical presentation suggests ischemic heart disease. Patients without ST elevation on the initial ECG who are ultimately found via further testing (e.g., elevated cardiac biomarkers, stress testing, or other tests) to have undergone an MI are diagnosed as having had non-ST elevation myocardial infarction (NSTEMI). Patients without ST elevation on the initial ECG who subsequently show evidence (e.g., by stress testing) of reversible myocardial ischemia are usually ascribed the diagnosis of unstable angina. Pending the results of further testing, patients without ST elevation whose clinical presentation suggests a cardiac etiology are typically considered to have ACS.
Although the standard ECG is critically important in the initial evaluation of patients with ACS, it is limited in its ability to correctly identify all patients with acute ischemic heart disease. False-positive test results are likely to lead to further testing or initiation of treatment, or both, whereas false-negative test results may lead to adverse outcomes associated with delay or withholding of potentially life-saving interventions. New devices that seek to improve on the standard ECG’s capabilities in the evaluation of patients presenting with chest pain have been proposed. An enhanced ECG-based test that allows a patient with ACS to be accurately identified could potentially limit the myocardial damage associated with delays in administering acute reperfusion treatment (by improving on the standard ECG’s true-positive rate), while possibly minimizing the use of potentially harmful invasive testing among patients who do not have clinically significant CAD (by improving on the standard ECG’s false-positive rate). The comparative technical efficacy and diagnostic accuracy efficacy of these technologies as well as their impact on clinical decisionmaking and patient outcomes, however, is uncertain.
The Coverage and Analysis Group at the Centers for Medicare and Medicaid Services (CMS) requested this report from the Technology Assessment Program (TAP) at the Agency for Healthcare Research and Quality (AHRQ). AHRQ assigned this report to the Duke Evidence-based Practice Center (Contract No. HHSA 290-2007-10066 I). The purpose of this technology assessment is to summarize the clinical and scientific evidence for commercially available ECG-based signal analysis technologies used to evaluate patients with chest pain or other symptoms suggestive of ACS among patients at low to intermediate risk for CAD. Although some ECG-based technologies have been used for other purposes (e.g., detecting malignant arrhythmias), these are not the focus of the current report—as defined in our inclusion/exclusion criteria. Rather, this report focuses on patients who do not meet STEMI or STEMI-equivalent criteria on the standard 12-lead ECG.
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