More than 6 million emergency department visits a year in the United States are for chest pain.¹ While there are approximately 1.1 million hospitalizations a year for acute coronary syndrome (ACS) in the United States, only approximately 30 percent of cases are ST-elevation myocardial infarctions.² The remaining 70 percent are diagnosed with unstable angina (UA) or non–ST-elevation myocardial infarction (NSTEMI). Risk stratification of chest pain patients with concern for ACS is of high concern in the emergency department. The American Heart Association (AHA) current guidelines recommend prompt management and possibly invasive strategies for patients with UA and NSTEMI who present with high-risk features.³ Often in the ED setting, chest pain patients have a nondiagnostic electrocardiogram (ECG), and initial cardiac biomarkers can be negative even with significant coronary artery occlusion.

Novice sonographers may have difficulty obtaining clear views and should not base decisions on suboptimal imaging. Even for the experienced ED sonographer, differentiating between new and old RMWAs can be extremely challenging.

Investigation of regional wall motion abnormalities (RWMAs) is a Class I recommendation by the AHA in the hands of trained echocardiogram technicians.⁴ The goal is to identify patients with RWMAs likely representing a significant occult coronary artery thrombosis not evident by symptoms, ECG, or initial cardiac biomarkers that could then benefit from an invasive intervention. Previous studies suggest that if a RWMA is present, a large area of myocardium is at risk for death.^5–7 Initial studies have shown good sensitivity and specificity of the identification of RWMAs for coronary ischemia in the ED setting.^8,9 Most of these studies were performed by trained ECG technicians or cardiologists. However, several articles recently described emergency physicians of various levels of training being capable of identifying RWMAs.^10,11 A case series described three cases in which emergency physicians identified RWMAs in patients with equivocal ECGs; all the cases went to cardiac catheterization partly based on the point-of-care echocardiography (POC echo) detecting RWMA and were found to have significant single-vessel coronary disease requiring intervention.¹²

(click for larger image) Figure 1: Appropriate probe positioning and corresponding ultrasound image of A) PLAX, B) PSAX, and C) A4C.

Clinical Indications for Performing POC Echo for RWMAs

Evaluation for RWMAs should promptly occur when the emergency physician has a high concern for UA or NSTEMI by history and physical examination with an equivocal ECG for cardiac ischemia.

Anatomy

For simplicity, the traditional 17-wall motion segment identification on ECG has been