Non-Invasive Imaging Tests for the Evaluation of Low Risk Patients in Chest Pain Units: Availability, Contributions and Drawbacks in Real Practice

Abstract

Patients presenting with chest pain or other symptoms consistent with myocardial ischemia are a common problem throughout the world. In the United States alone, there are over 8 million visits to the emergency department (ED) for chest pain annually, such that it is the secondmost frequent cause of adult ED visits. The presence of hemodynamic stability or ischemic electrocardiogram (ECG) changes identifies a high risk cohort; in the absence of these, the majority of the remaining patients are at lower risk for an acute coronary syndrome (ACS), and can be further risk stratified based on symptoms and history of coronary disease. The challenge to clinicians is rapidly and accurately identifying patients from this group who actually have unsuspected ACS. Failure to detect ACS patients can lead to inadvertent ED discharge, a situation associated with significantly increased morbidity and mortality, with resultant substantial liability. In an effort to improve risk stratification and identification of ACS and other serious conditions in the ED, a wide array of new imaging techniques have been applied, each with potential advantages and disadvantages. With all of these modalities, clinical judgment is essential for optimal application and interpretation. The simplest test for evaluating chest pain patients is the exercise treadmill test without imaging. Although very early exercise stress testing (ETT), prior to complete exclusion of myocardial infarction (MI), has been applied in some centers successfully, most would be reluctant to exercise a patient without serial markers and symptom resolution. Additional limitations of an ETT alone strategy include baseline ECG changes precluding the ability to interpret the ECG, and exercise tolerance insufficient to exclude ischemia with high confidence. In contrast to ETT, acute imaging is typically applied to patients with and without ongoing symptoms, frequently with only one set of cardiac markers. Advantages of acute imaging include more