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5 Transthoracic Windows andViews
Fig. 5.5 Parasternal
short-axis (PSAX) aortic
valve level
55
The apical short-axis view at the level of the
aorta is obtained by fanning or sliding the probe
toward the base of the heart (toward the right
shoulder). This view is helpful when assessing
for aortic or pulmonary valve pathology.
Imaging Tips
As with the PLAX view, gently sliding or tilting
the probe up or down rib spaces and slight rotation of the probe may be needed to optimize the
correct anatomical view.
Pearls and Pitfalls
• If the beam traverses the heart obliquely, the
LV can be transected obliquely, making the
cavity appear oval or D-shaped which may
give an inaccurate EF.
Apical: A4C, A5C, A2C, A3C
The apical viewing windows give attention to
ow through the valves, as well as comparisons
and evaluations for ventricular and atrial sizes. In
these views, the entire atria and ventricle should
be in view. These viewing windows are generally
best seen in the left lateral position, although
most patients in the supine position will have
adequate viewing windows.
Apical Four-Chamber View (A4C)
External Anatomy
To obtain the A4C view, the ultrasound probe is
traced laterally along the left fth intercostal
space to the anterior axillary line with the probe
marker facing the patient’s left side (3 o’clock)
position. Slight rotation or fanning may need to
be utilized to optimize the correct anatomical
view. In some patients, the probe may have to
slide more medially or laterally to fully view the
examined structures. The point of maximum
impulse (PMI), if palpable, is also a useful landmark to start with before placing the transducer
on the chest.
Sonographic Anatomy
In this view, the ultrasound beam passes through
the apex of the heart with the right and left ventricles, tricuspid valve, mitral valve, and right and
left atria fully in view. The septum should be
lined up vertically in the center of the screen
(Fig.5.6, Video 5.6).
56
Fig. 5.6 Apical
four-chamber view
(A4C)
N. Panebianco and M. O’Neil
Scanning Tips
If the four chambers are visible but the septum is
not vertical, fan the probe so that the beam is
pointing toward the right shoulder (and the tail of
the probe is pointing toward the left hip). If the
ventricles are visualized but the atria are not, try
decreasing the angle of the probe (atten out the
probe) relative to the chest wall. If the atria are
well seen but the ventricles are not, try the opposite maneuver just described. If one side of the
heart dominates the image (right or left) try rotating the probe to even out the cavities.
Pearls and Pitfalls
• As with the parasternal windows, if the lung is
obstructing the echocardiography window,
attempt to roll the patient onto their left side.
• If the probe marker is inadvertently ipped,
one could falsely diagnose right heart strain
because the right side of the heart will appear
larger than the left side. There are several ana-
tomic structures that should be noted to pre-
vent this mistake.
– First, the right heart will have the modera-
tor band seen at the RV apex.
– Second, the tricuspid valve annulus is
slightly more anterior than the left.
– Lastly, sliding slightly cephalad should
reveal the aortic valve outow tract, which
will conrm the location of the left
ventricle.
– When breast tissue is encountered, place
the probe under it rather than trying to
scan through it. Supportive garments and
EKG stickers should be removed, and
monitor leads should be relocated outside
the scanning window. Remember to drape
your patient with towels to preserve
modesty.
Apical Five-Chamber View (A5C)
External Anatomy
The AC5 view is often obtained at the same anatomic location as the AC4, in the left fth intercostal space in the mid-axillary line or just
inferior to the nipple by simply fanning the probe
cephalad. If rib shadows are encountered, move
the probe cephalad one rib space.
Sonographic Anatomy
The image obtained in this view is similar to the
A4C; however, the left ventricular outow tract
and aortic valve will be seen connecting to the
left ventricle. The left atrium view may be foreshortened when obtaining the image in this window (Fig.5.7, Video 5.7).
5 Transthoracic Windows andViews
Fig. 5.7 Apical
ve-chamber view
(A5C)
57
Scanning Tips
The tips for this view are similar to those for the
A4C.If a rib shadow is encountered when fanning the cephalad to obtain the image, consider
moving the probe up one rib space. This movement may cause the ventricles to be cut short and
the atria to come out of view.
Pearls and Pitfalls
• This view is commonly used to calculate the
cardiac stroke volume and output. Being off-
plane can cause variability in serial Doppler
measurements and erroneous calculations.
• In patients with a low body mass index, it may
be challenging to obtain enough skin contact
to generate an adequate image. In this sce-
nario, use more gel or a step-off to get better
skin contact.
Apical Two-Chamber View (A2C)
External Anatomy
Same as the AC4 view.
Sonographic Anatomy
From the A4C view, rotate the probe 90° counterclockwise so that the indicator is toward the head.
In this view, the ultrasound beam passes through
the apex of the heart, the left ventricle, the mitral
valve, and the left atria. In the A4C view, the left
ventricular septum and lateral wall are seen. In
the A2C view, the left ventricular inferior wall is
seen on screen left, and the anterior wall is seen
on screen right. The right ventricle should not be
visualized in this view (Fig.5.8, Video 5.8).
Scanning Tips
The scanning tips for this window are similar to
those for the A4C view.
Pearls and Pitfalls
• Over- or under-rotation can yield inadequate
visualization of the pertinent structures.
Apical Three-Chamber View (A3C)
External Anatomy
The external anatomy is often the same as for the
A4C and A2C views.
Sonographic Anatomy
To obtain this view, rotate the probe counterclockwise from the A2C view (about 60°) until
the aortic outow tract is seen connecting to the
left ventricle. When in plane, this view should
look very similar to the PSLA image, however
58
Fig. 5.8 Apical
two-chamber view
(A2C)
Fig. 5.9 Apical
three-chamber view
(A3C)
N. Panebianco and M. O’Neil
visualized from the apex of the heart. The sonographic anatomy will include the left ventricle,
right ventricle, interventricular septum, left ventricular outow tract, and left atrium (Fig.5.9,
Video 5.9).
Scanning Tips
The scanning tips for this view are similar to
those of the A4C and A2C. Over-rotation can
cause inadequate imaging. Similarly, if not on the
plane, the size of the LV and RV can be
misinterpreted.
Pearls and Pitfalls
• This view is particularly helpful when assessing the left ventricular outow tract.
• If lung artifact obscures, the view has the
patient exhale completely.
5 Transthoracic Windows andViews
59
Subcostal: SC4, SC Long Access, IVC
Many of the cardiac views described in the parasternal and apical windows can also be obtained
in the subcostal window. In patients with COPD
or asthma, cardiac structures may be elongated
and midline, leaving the subcostal window as the
only window for adequate cardiac imaging. This
window is unique from the other windows previously described because it includes anatomy
below the diaphragm such as the inferior vena
cava (IVC), liver, and peritoneum.
Subcostal Four-Chamber View (SC4)
External Anatomy
The subcostal four-chamber view is obtained by
placing the probe with the probe marker to the
patient’s left (3 o’clock position), just below the
bony xiphoid process, and often slightly to the
patient’s right using the liver as a sonographic
window. The probe should be pressed almost at
against the abdomen to clear the bony structures,
and the operator may need to overhand the probe
to apply the appropriate amount of pressure and
angle to obtain adequate images.
Sonographic Anatomy
In this view, the ultrasound beam rst passes
through the liver, then both the right atria and
right ventricle, and subsequently the left atria
and left ventricle. The echogenic pericardium
should be ush against the myocardium and
indistinguishable from adjacent structures.
Physiologic pericardial effusion may be seen
anteriorly by the right atrium. This view is useful for assessing pericardial effusion and tamponade. Additionally, it is often the best location
to assess the right ventricular free wall thickness
(Fig.5.10, Video 5.10).
Scanning Tips
Unlike the other views, images in the subcostal
window are often best obtained when the patient
is completely supine and not rolled. If a patient
cannot tolerate a supine position, consider placing the patient in reverse Trendelenburg to let
gravity bring the heart closer to the probe. Chest
and abdominal wounds and bandages may interfere with this window and should be removed
when appropriate. In patients who are gravid, and
have signicant abdominal distention, ascites, or
abdominal tenderness, this view may not be
obtainable.
Fig. 5.10 Subcostal
four-chamber view
(SC4)
60
N. Panebianco and M. O’Neil
Pearls and Pitfalls
• In an awake patient, having them take a deep
breath and hold it may improve imaging.
• Having the patient bend their knees may
loosen the abdominal musculature and allow
the examiner to press hard enough to get under
the bony sternum.
• An image is in the plane when the four cardiac
chambers, tricuspid, and mitral valves are in
view. Off-axis images can over or underestimate the size of chambers.
• An epicardial fat pad can be mistaken as a
pericardial effusion. Epicardial fat will not be
circumferential, moves with the cardiac cycle,
and often has internal echoes.
• Abdominal ascites can be mistaken for pericardial effusion.
Subcostal Long Axis IVC
External Anatomy
The external anatomy for the long-axis view of
the IVC is the same as for the subcostal view of
the heart. The probe is rotated so that the marker
is facing the cephalad (12 o’clock position) and
tilted upward toward the heart.
If bowel gas, wounds, or other factors limit
this window, scanning through the liver may pro-
vide an adequate view of the IVC.To do this, line
the probe up with the xiphoid process and then
slide laterally to the right toward the midclavicular line, between the ribs, angled cephalad, with the liver as the sonographic window.
Sonographic Anatomy
In this view, the IVC is visualized passing through
the diaphragm into the right atrium. The hepatic
veins converge with the IVC just before the vessel enters the thoracic cavity. Once the appropriate imaging level has been identied, the hand
should be held still to assess the morphology and
collapsibility of the great vessel (Figs.5.11 and
5.12, Videos 5.11 and 5.12).
Scanning Tips
As described above, if the subcostal window is
inadequate, the right intercostal window may be
useful. If bowel gas is preventing, adequate imaging gentle pressure may be applied with the transducer to move it out of the scanning eld;
however, attention must be paid to not press so
hard to cause collapse of the IVC.Adjusting the
frequency, depth, gain, and dynamic range
machine settings may be necessary to visualize
the abdominal IVC.To quantify the IVC variation through the respiratory cycle, M-Mode may
be useful.
Fig. 5.11 Subcostal
long axis IVC
5 Transthoracic Windows andViews
Fig. 5.12 Subcostal
short axis IVC
61
Pearls and Pitfalls
• The abdominal aorta can be mistaken for the
IVC, particularly in patients with hypovolemia.
There are several strategies to distinguish the
abdominal aorta from the IVC. The hepatic
veins course through the liver and join the IVC
just before the vessel passes through the diaphragm, while the celiac trunk and superior
mesenteric arteries branch from the aorta. The
IVC is on the patient’s right relative to the
abdominal aorta, which may be more easily recognized when scanning in the transverse plane.
The walls of the aorta are generally thicker than
that of the IVC; however, this relative size may
be difcult to distinguish on ultrasound.
• The IVC pulsates and this nding cannot be
used to distinguish the IVC from the aorta.
• In patients with intra-abdominal hypertension,
the IVC may be compressed.
• Increased right heart pressures and tamponade
physiology will dilate the IVC.For this reason,
the IVC alone cannot be used to assess the
volume status.
Suprasternal/Supraclavicular View
This sonographic window is valuable for the
assessment of the great vessels that are typically
obscured by the bones of the anterior chest. It is
often one of the more challenging windows to
obtain images from because of patient anatomy,
patient discomfort, and transducer size. When
setting up for the exam, placing a pillow or prop
behind the shoulders and having the patient turn
their head gently to the left may open the window
and make more room for the transducer and its
cord. Suprasternal imaging may not be possible
in patients in cervical traction or with a tracheostomy or prior tracheostomy scar tissue. If the
patient is orally intubated, be mindful to position
equipment away from the scanning window so as
not to dislodge any items.
External Anatomy
Apply copious gel to the suprasternal notch to
reduce the amount of pressure needed on the
neck. Place the probe in the suprasternal notch
with the probe indicator toward the 1 o’clock
position. If imaging is inadequate, the right
supraclavicular is an alternative location for
scanning.
Sonographic Anatomy
A long-axis view of the ascending aorta, aortic
arch, descending thoracic aorta, and the origins
of the right brachiocephalic, left common carotid,
and left subclavian artery may be seen. The corresponding venous structures are positioned
superior to the aortic arch. The superior vena
62
Fig. 5.13 Suprasternal
aortic arch
N. Panebianco and M. O’Neil
cava may be visualized on the left of the ascending aorta, while the right pulmonary artery is
identied as inferior to the aortic arch.
The short-axis view is obtained by rotating the
probe 90° from the position where the optimized
long-axis image was obtained (Fig.5.13, Video
5.13).
Imaging Tips
As described above, attention to patient positioning and copious gel can greatly improve imaging
in this location. Once the aorta is visualized, the
probe may need to be rotated clockwise or counterclockwise to bring the anatomy into the plane.
In an awake patient, if the lung is obscuring the
image, have the patient completely exhale and
hold their breath.
Pearls and Pitfalls
• Mirror and side-lobe artifacts can confound
the interpretation of thoracic aorta imaging
and create the appearance of pathology (par-
ticularly a dissection ap) when there isn’t
one. Optimize depth, gain, and the focal zone
to reduce artifacts. Pathologic ndings
should persist when assessed in orthogonal
planes.
• Small dissections and other aortic pathology
may be difcult to see on transthoracic echocardiography. Consider using alternative
imaging modalities, such as computed tomography and transesophageal echocardiography,
given the limitations of this exam.
Key Points
• This chapter describes the fundamental twodimensional views of echocardiography with
a systematic description of the patient’s external surface anatomy, sonographic anatomy,
scanning tips, and pearls and pitfalls.
• The information in this chapter provides
insight into commonly encountered difculties in obtaining views and strategies for troubleshooting them when they arise.
Transthoracic M-Mode Echocardiography
BeckyBurk
6
Learning Objectives
1. Know the advantages m-mode has over 2D
imaging in specic instances and applications.
2. Be familiar with common m-mode images in
echocardiography.
Introduction toM-Mode
M-mode, or “motion” mode, records ultrasound
data from a single scan line and plots it sequentially over time. The displayed image shows time
on the x-axis versus depth on the y-axis. Thus,
the change in the depth of cardiac structures
along the scan line is observed over time. The use
of ultrasound to characterize the heart began in
the 1950s. M-mode was the original echocardiogram modality, and it was dominant until the
1970s when 2D imaging was developed [1].
Some echocardiographers consider m-mode an
historical relic, but it has two key advantages
which make it a relevant part of the modern
echocardiogram.
The rst and major advantage of m-mode is its
high temporal resolution. This characteristic
makes it the mode of choice to analyze rapidly
moving structures, such as cardiac valves.
Temporal resolution is dened by the frame
B. Burk (*)
Renown Health, Reno, NV, USA
rate, which is the number of images displayed
per second. A higher frame rate results in more
granular and smoother imaging over time. A single image, or “frame,” is generated once ultrasound waves have been emitted and “listened to”
for each scan line. Therefore, the frame rate is
inversely proportional to the number of scan
lines. Unlike 2D imaging, which requires many
scan lines, m-mode only has a single scan line, so
the frame rate is very high (Fig.6.1, artist gure
showing frame rate). M-mode frame rates are
typically around 1000–2000 frames/s, as compared to 2D imaging in which a typical frame rate
is 40–80frames/s [1]. For rapidly moving structures, such as valves, a few milliseconds may
result in a meaningful change in position which
can be reliably depicted by the high frame rate of
m-mode.
The second advantage of m-mode is that the
movements of cardiac structures over time are
displayed in a single image. This contrasts with
2D imaging, in which the echocardiographer
scrolls through a cine loop comprising multiple
images to observe movement over time. Thus,
m-mode is well suited for examining cardiac
changes throughout the respiratory cycle, such as
the collapse of the inferior vena cava.
To obtain an m-mode image on modern equipment, the echocardiographer starts with a 2D
“scout” image. The echocardiographer then
moves the cursor over the structures of interest
and m-mode is initiated. Precise cursor place-
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025
M. J. Lanspa, A. T. Levinson (eds.), Echocardiography and Ultrasonography in the ICU,
Respiratory Medicine, https://doi.org/10.1007/978-3-031-80038-2_6
63
64
Panel A
P
anel B
B. Burk
Low
frame
rate
High
frame
rate
Time
Fig. 6.1 Temporal resolution. Frame rate is the number
of images displayed per second. A low frame rate
(panel a, top row) results in a choppy video with poor
temporal resolution. A high frame rate (panel a, bottom
row) results in a smooth video that clearly shows cardiac movement over time. A single frame is generated
ment is critical. If the cursor is placed incorrectly,
measurements made using m-mode tracings are
inaccurate. Once m-mode is initiated, the display
of depth vs. time is generated. The display is frozen and analyzed once the movements of interest
have been captured.
One limitation of m-mode is that the
m-mode scan line is parallel to the angle of
insonation, which does not necessarily align
with the cardiac structures of interest.
“Anatomic m-mode” is a digital postprocessing technique that eliminates this problem by
allowing an m-mode cursor to be oriented in
any direction [2]. However, because anatomic
m-mode relies on 2D images, it also eliminates the main benefit of m-mode, which is
high temporal resolution (Box 6.1).
New image
generated every
12−25 msec
once ultrasound waves have been emitted and received
for each scan line, so the number of scan lines and
frame rate are inversely proportional. 2D imaging has
many scan lines, so the frame rate is lower while
m-mode has a single scan line, so the frame rate is
higher (panel b)
New image
generated every
0.5−1 msec
Box 6.1 Benets of M-Mode
1. High temporal resolution. M-mode is
ideal for assessing rapidly moving
structures.
2. Shows depth vs. time on a single image.
Observations can be made about cardiac
changes throughout the respiratory
cycle without cycling through a cine
loop.
Color Doppler can be overlayed onto m-mode
to create “color m-mode.” Color m-mode has
various applications, but it can be particularly
helpful in identifying the precise time that a valve
opens or closes. Therefore, color m-mode can be