Download Teresa S. Wu, MD, FACEP Director, EM Ultrasound Program

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Teresa S. Wu, MD, FACEP
Director, EM Ultrasound Program & Fellowship
Co-Director, Simulation Based Training Program & Fellowship
Maricopa Medical Center
Simulation Curriculum Director
Associate Professor, Emergency Medicine
University of Arizona, College of Medicine-Phoenix
Background
• Bedside echocardiography can provide invaluable information during the
assessment of patients presenting with chest pain, shortness of breath, dizziness,
shock, or acute cardiopulmonary arrest.
• Physical exam findings and vital signs can often be misleading in the
management of critically ill patients.
• A bedside ultrasound examination can be used to evaluate cardiac contractility,
estimate ejection fraction, assess for the presence of a pericardial effusion,
determine if cardiac tamponade physiology is present, and help guide
procedures such as pericardiocentesis and transvenous pacemaker wire
placement.
• Information can be rapidly obtained at the bedside, and the study can be
repeated to assess the effects of treatment being rendered.
Probe Selection
• Use the low frequency (3-5 MHz) phased array transducer (Image 1).
Image 1: Low frequency phased array transducer.
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Performing the Scan
• The patient should be lying supine or as flat as he/she can tolerate given the
clinical presentation.
• There are three main cardiac windows that are utilized in bedside
echocardiography: the parasternal view, the apical view, and the subxiphoid view
(Image 2).
Image 2: Probe positions used during a standard bedside cardiac ultrasound.
1 = parasternal, 2 = apical, and 3 = subxiphoid.
Parasternal Views of the Heart
• In the parasternal window, a long-axis view and a short-axis view of the heart
can be obtained.
• Place the probe in an oblique orientation just to the left of the sternum, along
the 3rd to 4th intercostal space.
• Point the indicator marker towards the patient’s right shoulder (Image 3).
• Use the cardiac presets on your ultrasound machine to ensure that the
indicator marker is to the right of the ultrasound image on the screen.
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Image 3: Probe position for a parasternal long-axis view of the heart. Note that
the probe indicator is pointing towards the patient’s right shoulder and that the
indicator marker on the screen is to the right side of the image.
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To improve your parasternal view of the heart, position the patient in a left
lateral decubitus position with their left arm extended over their head.
This position will bring the heart closer to the chest wall, away from the
sternum and lung, and will open up the rib spaces for an enhanced view of
the heart.
On a parasternal long-axis view of the heart, the right ventricle (RV), left
ventricle (LV), left atrium (LA), septum, aortic outflow tract (Ao), aortic valve,
and mitral valve (MV) can be assessed (Image 4).
Note that the right atrium is not visible in the parasternal long-axis view of the
heart.
Image 4: Parasternal long-axis view of the heart. Note that the probe indicator is
pointing towards the patient’s right shoulder and that the indicator marker on the screen
is to the right side of the image.
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The descending aorta can be seen as a hypoechoic circle just
posterior/farfield to the left atrium in the parasternal long-axis view.
To obtain a parasternal short-axis view of the heart, rotate the probe 90°
clockwise towards the patient’s left shoulder (Image 5).
Image 5: Probe position for a parasternal short-axis view of the heart. Note that
the probe indicator is pointing towards the patient’s left shoulder and that the
indicator marker on the screen is to the right side of the image.
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The parasternal short-axis view of the heart provides a cross-sectional image
through the heart.
Sliding the probe superiorly will provide a cross-sectional image of the aortic
valve, right ventricular outflow tract (RVOT), right atrium (RA), left atrium (LA),
pulmonary artery (PA), tricuspid valve (TV), pulmonary valve (PV), and
descending aorta (Image 6).
Note that the normal, tricuspid aortic valve will appear as the “Mercedes Benz
Sign” on a parasternal short-axis view (Image 6).
Image 6: Parasternal short-axis view of the heart at the level of the aortic valve.
Note that the probe indicator is pointing towards the patient’s left shoulder and
that the indicator marker on the screen is to the right side of the image.
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Siding the probe inferiorly and laterally towards the patient’s point of maximal
impulse, will provide a cross-sectional view of the heart at the level of the
mitral valve.
In this view, the mitral valve will appear as a “fish-mouth” within the left
ventricle (Image 7).
At this level, the parasternal short-axis view will allow you to assess the right
ventricle, left ventricle, and mitral valve (Image 7).
Image 7: Parasternal short-axis view of the heart at the level of the mitral valve. The
mitral valve looks like a “fish-mouth” opening and closing. Note that the probe indicator
is pointing towards the patient’s left shoulder and that the indicator marker on the
screen is to the right side of the image.
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The parasternal views of the heart can be difficult in patients with underlying
pulmonary disease and in patients with an abundance of soft tissue along
their anterior chest wall.
Apical Views of the Heart
• In addition to the parasternal views of the heart, an apical view of the heart
can be obtained during bedside echocardiography.
• To obtain an apical view of the heart, slide the probe laterally and inferiorly
down towards the point of maximal impulse on the patient’s chest (Image 8).
Image 8: Probe position for an apical view of the heart. Note that the probe
indicator is pointing towards the patient’s left axilla and that the indicator marker
on the screen is to the right side of the image.
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To obtain the proper apical view of the heart, it often helps to start with the
parasternal short-axis view and follow the left ventricle outward towards the
apex.
Once you see the hyperechoic, circular anterolateral papillary muscle (ALPM)
and posteromedial papillary muscle (PMPM) of the mitral valve, start directing
your ultrasound beams up towards the patient’s right shoulder (Image 9).
You should be at or near the PMI (point of maximal impulse).
With the beams angled towards the patient’s right shoulder, you should see a
4-chamber view of the heart on the screen (Image 10).
Image 9: Parasternal short-axis view of the heart at the level of the papillary muscles
(ALPM = anterolateral papillary muscle; PMPM = posteromedial papillary muscle). Note
that the probe indicator is pointing towards the patient’s left axilla and that the indicator
marker on the screen is to the right side of the image.
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Please do not copy or distribute them without written consent from the author. "
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The apical 4-chamber view of the heart allows you to evaluate the right atrium
(RA), right ventricle (RV), tricuspid valve (TV), left ventricle (LV), left atrium
(LA), and mitral valve (MV) (Image 10).
Image 10: Apical 4-chamber view of the heart. Note that the probe indicator is
pointing towards the patient’s left axilla and that the indicator marker on the
screen is to the right side of the image.
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Once you have a good apical 4-chamber view, tilting your probe upwards and
anteriorly will provide a view of the aortic outflow tract coming off of the left
ventricle. This is the 5th chamber of an apical 5-chamber view of the heart
(Image 11).
Image 11: Apical 5-chamber view of the heart. (LV= left ventricle, RV = right
ventricle, Ao = aortic outflow tract, RA = right atrium, LA = left atrium). Note that
the probe indicator is pointing towards the patient’s left axilla and that the
indicator marker on the screen is to the right side of the image.
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Please do not copy or distribute them without written consent from the author. "
Cardiac Ultrasound
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The apical 5-chamber view of the heart allows for assessment of the aortic
outflow tract for aortic regurgitation or stenosis with color-Doppler imaging.
The apical views of the heart can be limited by patient body habitus and in
patients with abundant breast tissue.
Subxiphoid View of the Heart
• The third commonly utilized view in bedside echocardiography is the
subxiphoid view.
• In this view, the probe is placed below the xiphoid process, flat against the
patient’s abdominal wall, with the indicator pointing towards the patient’s right
side.
• Angle the beams of the ultrasound probe underneath the xiphoid process,
towards the patient’s left shoulder (Image 12).
Images 12: Probe position for a subxiphoid view of the heart. Note that the
probe indicator is pointing towards the patient’s right side and that the indicator
marker on the screen is to the left side of the image.
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Cardiac Ultrasound
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Image 13: Subxiphoid view of the heart. Liver parenchyma in the nearfield
creates an acoustic window in this approach. Note that the probe indicator is
pointing towards the patient’s right side and that the indicator marker on the
screen is to the left side of the image.
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The subxiphoid view of the heart is the traditional cardiac view used during
the EFAST exam of trauma, and uses the liver as an acoustic window.
The subxiphoid view should not be used in patients with epigastric abdominal
pain or a gas-filled stomach, which may obscure adequate views of the
cardiac chambers and surrounding structures.
Normal Sonographic Anatomy
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Image 14: Normal parasternal long-axis view of the heart. Note that the
probe indicator is pointing towards the patient’s right shoulder and that the
indicator marker on the screen is to the right side of the image.
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Please do not copy or distribute them without written consent from the author. "
Cardiac Ultrasound
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Image 15: Normal parasternal short-axis view of the heart at the level of the
aortic valve. Note that the probe indicator is pointing towards the patient’s left
shoulder and that the indicator marker on the screen is to the right side of the
image.
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Image 16: Normal parasternal short-axis view of the heart at the level of the
mitral valve. Note that the probe indicator is pointing towards the patient’s left
shoulder and that the indicator marker on the screen is to the right side of the
image.
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Image 17: Normal parasternal short-axis view of the heart at the level of the
papillary muscles. Note that the probe indicator is pointing towards the
patient’s left shoulder and that the indicator marker on the screen is to the
right side of the image.
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Please do not copy or distribute them without written consent from the author. "
Cardiac Ultrasound
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Image 18: Normal apical 4-chamber view of the heart. Note that the probe
indicator is pointing towards the patient’s left axilla and that the indicator
marker on the screen is to the right side of the image.
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Image 19: Normal apical 5-chamber view of the heart. Note that the probe
indicator is pointing towards the patient’s left axilla and that the indicator
marker on the screen is to the right side of the image.
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Image 20: Normal subxiphoid view of the heart. Note that the probe indicator
is pointing towards the patient’s right side and that the indicator marker on the
screen is to the left side of the image.
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Please do not copy or distribute them without written consent from the author. "
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Image 21: Measuring end-diastolic diameter (EDD) and end-systolic diameter
(ESD) in a parasternal long-axis view in B-mode. Fractional shortening can
be calculated by the equation: Fractional shortening (%) = [(EDD-ESD)/EDD]
x 100. A fractional shortening of 35-40% indicates a normal ejection fraction.
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Image 22: Calculating fractional shortening in M-mode using the equation:
Fractional shortening (%) = [(LVEDD-LVESD)/LVEDD] x 100. A fractional
shortening of 35-40% indicates a normal ejection fraction. (LVEDD = leftventricular end-diastolic diameter, LVESD = left-ventricular end systolic
diameter).
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Cardiac Ultrasound
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Image 23: Calculating ejection fraction using E-Point Septal Separation
(EPSS). With the cursor overlying the distal tip of the anterior mitral leaflet,
assess the M-mode tracing for a characteristic pattern of two repeating waves.
The taller first wave is the E-wave, which reflects the initial opening of the
mitral valve to allow passive filling of the left ventricle. The smaller second
wave is the A-wave, which corresponds to left atrial contraction at the end of
diastole. E-Point Septal Separation is the distance between the E-point and
the interventricular septum (IVS). As cardiac contractility decreases, EPSS
increases. An EPSS > 1 cm correlates with a generally low ejection fraction.
Notable Pathology
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Image 24: Pericardial effusion seen on a subxiphoid view of the heart. Note
that the effusion is seen circumferentially around the heart.
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Image 25: Pericardial effusion seen on a parasternal long-axis view of the
heart. Note that the effusion is circumferential and seen both anteriorly and
posteriorly to the heart.
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Image 26: Large pericardial effusion and right ventricular collapse seen on an
apical 4-chamber view of the heart. End-diastolic right ventricular collapse is
one of the earliest sonographic signs seen with cardiac tamponade.
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Cardiac Ultrasound
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Image 27: An abnormal fractional shortening of the left ventricle seen in Mmode. Fractional shortening can be calculated using the equation: Fractional
shortening (%) = [(LVEDD-LVESD)/LVEDD] x 100. A fractional shortening of
35-40% indicates a normal ejection fraction. (LVEDD = left-ventricular enddiastolic diameter, LVESD = left-ventricular end systolic diameter).
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Image 28: An abnormal ejection fraction seen with E-Point Septal Separation
(EPSS). With the cursor overlying the distal tip of the anterior mitral leaflet,
assess the M-mode tracing for a characteristic pattern of two repeating waves.
The taller first wave is the E-wave, which reflects the initial opening of the
mitral valve to allow passive filling of the left ventricle. The smaller second
wave is the A-wave, which corresponds to left atrial contraction at the end of
diastole. E-Point Septal Separation is the distance between the E-point and
the interventricular septum (IVS). As cardiac contractility decreases, EPSS
increases. An EPSS > 1 cm correlates with a generally low ejection fraction.
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Please do not copy or distribute them without written consent from the author. "
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Image 29: Parasternal long-axis view of the heart in a patient with a large
pulmonary embolism. Note the dilated right ventricle (RV) and right atrium
(RA) compressing the left ventricle (LV) and left atrium (LA).
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Image 30: Parasternal short-axis view of the heart in a patient with a large
pulmonary embolism. Note the dilated right ventricle (RV) compressing the
septum into the left ventricle (LV). The compressed left ventricle
demonstrates the “D-sign”.
Pearls and Pitfalls in Performing a Bedside Cardiac Ultrasound
• When performing a bedside cardiac ultrasound, there are two main ways to
approach orientation. Traditionally, cardiologists and echocardiographers
have set the scan so that the indicator on the ultrasound screen is to the right
of the ultrasound image. During the scan, the parasternal long-axis view is
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obtained by aiming the probe indicator towards the patient’s right shoulder.
This will place the apex of the heart on the left side of the screen. In the shortaxis view, the probe indicator is pointed towards the patient’s left shoulder. In
the apical view, the indicator is oriented towards the patient’s left axilla.
In some emergency and radiology references, the ultrasound machine is set
so that the indicator marker on the screen is to the left of the image. When
the indicator marker is on the left side of the image, the orientation marker on
the probe must be positioned 180° in the opposite direction of that noted in
standard cardiology views. With this configuration, the probe marker will be
pointed towards the patient’s left hip in the parasternal long axis view. This
will still place the apex of the heart on the left side of the screen. The probe
marker should be pointed towards the patient’s right hip during the
parasternal short axis view and apical view if the indicator marker is on the
left side of the ultrasound screen.
When obtaining a parasternal view of the heart, place the patient on their left
side and have them extend their left arm over their head. This opens up the
rib spaces and brings the heart closer to the chest wall and the ultrasound
probe.
When obtaining a subxiphoid view of the heart, have the patient bend their
lower extremities at the hips and knees. This will help relax their abdominal
muscles and allow for the probe to be pushed posteriorly underneath the
xiphoid process.
Take your time performing the cardiac ultrasound. Small movements with the
probe will often be all that is necessary to bring the desired view onto the
screen.
Maximize the frame rate setting on your ultrasound machine to optimize views
of the rapidly moving cardiac structures.
Remember that cardiac tamponade can develop with as little as 50 mL of fluid
accumulating rapidly within the pericardial sac.
Chronic pericardial effusions allow for the heart to adjust to the increased
pericardial pressures over time, and therefore, patients can have large
chronic pericardial effusions without cardiac tamponade physiology.
There are multiple formulas and ultrasound programs available to calculate
cardiac ejection fraction. For focused bedside echocardiography, evaluating
fractional shortening or EPSS are the most efficient and accurate ways to
assess a patient’s EF.
A pulmonary embolus must be large and clinically significant to cause dilation
of the right ventricle. If acute right ventricular enlargement is noted, consider
administering thrombolytics in the appropriate clinical setting.
To differentiate acute versus chronic right ventricular enlargement, measure
the diameter of the right ventricular free-wall. Acute right ventricular
enlargement will demonstrate a free-wall diameter <0.6 mm in width.
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For more bedside ultrasound tips and tricks,
check out the ultrasound app SonoSupport.
www.SonoSupport.com
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Please do not copy or distribute them without written consent from the author. "