What is the role of cardiac testing in the emergency department (ED)?

Updated: Nov 20, 2018
  • Author: Richard S Krause, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

The goal of cardiac testing in the emergency department (ED) setting is to help stratify patients thought to be at risk for symptomatic coronary artery disease, specifically for short-term complications such as myocardial infarction (MI) or sudden cardiac death (SCD). Risk stratification of chest pain patients in the ED or other outpatient settings also includes interpretation of the history, as well as findings of the physical examination, electrocardiogram (ECG) and, when indicated, cardiac biomarkers levels. Cardiac testing encompasses diagnostic coronary angiography (invasive) or a variety of noninvasive tests.

This article focuses on the physiology, technique, interpretation, and utility of common noninvasive cardiac testing modalities and their role in risk-stratifying ED patients and other outpatients. The tests reviewed include exercise stress testing; pharmacologic stress testing; myocardial perfusion imaging; stress echocardiography; and cardiac computed tomography (CT) scanning, magnetic resonance imaging (MRI), and positron emission tomography (PET) scanning. These noninvasive tests can be performed in an outpatient setting, in a physician's office, in a hospital, or in an observation unit, as well as for admitted inpatients.

An understanding of these tests is important to for two primary reasons. First, patients frequently present that have undergone prior noninvasive testing. Knowing the value and limitations of that testing can be valuable in the care of such patients. Second, with the relatively recent expansion of observation medicine, it has become the responsibility of emergency physicians to choose and utilize the results of noninvasive cardiac testing in many hospitals. Noninvasive cardiac testing is an important adjunct to the broader scheme used to risk stratify chest pain patients. Use of cardiac biomarkers alone without additional noninvasive testing has not been shown to confer a low-enough risk to safely discharge a large proportion of chest pain patients from the ED. [5, 6, 7]

Explicitly or implicitly, physicians use a Bayesian model to interpret the results of cardiac tests. They generate a pretest probability of disease for an individual patient based on history, ECG findings, laboratory results, and other clinical factors. Then, by using the sensitivity and specificity of a given test for the population of interest, a post-test probability is calculated which can guide decision making. In day-to-day practice, this is performed more qualitatively than quantitatively. In addition, this process is reflected in diagnostic protocols for chest pain.


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