Considerations, Caveats, and Limitations
When looking for RWMAs with POC echo, there are few notable caveats. 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. Previous infarctions may result in areas of thinned, akinetic, dyskinetic, or aneurysmal myocardium.15 Also, mechanical and electrical cardiac variants can mimic an acute RWMA. Specifically, focal myocarditis, left bundle branch block, paced rhythms, ventricular aneurysms, Takotsubo cardiomyopathy, and previous cardiac surgeries can all make the acute differentiation of RWMAs difficult. Clinicians performing more advanced echocardiography in the ED should be aware of these and other limitations before adjusting clinical care.
While POC echo to identify RWMAs cannot supplant patient history, clinical examination, ECGs, and cardiac biomarkers, it can provide a prompt bedside tool to help risk-stratify chest pain patients with a risk for myocardial ischemia. Identification of RWMAs may help stratify patients in need of prompt cardiology consultation (and/or comprehensive echocardiography), more frequent serial ECGs, rapid biomarker testing, and in certain cases early cardiac catheterization.
Dr. Johnson and Dr. Lovallo are in the department of emergency medicine at Alameda Health System’s Highland Hospital in Oakland, California.
Dr. Frenkel is in the department of emergency medicine at St. Paul’s Hospital in Vancouver, British Columbia.
Dr. Nagdev is director of emergency ultrasound at Highland Hospital in Oakland, California, and assistant clinical professor (volunteer) of emergency medicine at the University of California, San Francisco.
After reading this article, the physician should be able to:
- Describe the indications to evaluate for regional wall motion abnormalities (RWMAs).
- Perform focused point-of-care echocardiography.
- Identify anterior, inferior, and lateral RWMAs.
- Identify potential coronary artery occlusion based on RWMAs and electrocardiogram findings.
Probe Selection, Technique, and ECG Views
Patient positioning: The patient should lie supine or be placed in the left lateral decubitus position.
Probe selection: The low-frequency phased array transducer (5-1 MHz) is recommended. A curvilinear probe (5-2 MHz) can also be used but may be suboptimal.
- Parasternal long axis (PLAX): Place the transducer on the left chest near the sternum, with the indicator probe pointing to the patient’s right shoulder. Starting at the level of the nipples/areola, slide the probe down the left border of the sternum to find the best acoustic window. Minor rotation (either clockwise or counterclockwise) will allow for a clear PLAX view (see Figure 1A).
- Parasternal short axis (PSAX): After the parasternal long axis is obtained, rotate the probe 90 degrees in a counterclockwise direction until the probe indicator points to the patient’s right hip. Subtle cephalad/caudal movements of the transducer will allow for the best acoustic window (see Figure 1B). The sonographer should move the probe just distal to the mitral valve to the level of the papillary muscles to obtain an ideal view for detecting RWMAs.
- Apical four-chamber view (A4C): From the position of the parasternal long/short, slide the transducer laterally along the axis of the heart toward the apex. From this location, angle the beam toward the right scapula (with the probe marker toward the right hip). The goal is to have the transducer footprint at the cardiac apex, with the beam directed through both ventricles and atria. (The ultrasound view will ideally have the intraventricular septum oriented vertically in the center of the screen.) Once again, make subtle movements for the best acoustic window (see Figure 1C). This is often the most difficult view to obtain and generally requires the patient be positioned in the left lateral decubitus position. RWMAs are often evident on parasternal long and short, and the A4C view may not be needed if the other two views are obtained.
Anterior Regional Wall Motion Abnormality in a) Parasternal Long Axis and b) Parasternal Short Axis.
Inferior Regional Wall Motion Abnormality in a) Parasternal Short Axis and b) Apical Four Chamber.
Lateral Regional Wall Motion Abnormality in Parasternal Short Axis
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