Download Michael P. Mallin and Christine Butts

Emergency Cardiac
Ultrasound: Evaluation for
Pericardial Effusion and
Cardiac Activity
5 Michael P. Mallin and Christine Butts
KEY POINTS
• Emergency cardiac ultrasound is performed by the
emergency physician to assess for the presence of
cardiac activity, determine whether a pericardial
effusion is present, and answer other specific
questions.
• Echocardiography can be used during cardiac arrest to
guide resuscitation decisions.
• Emergency use of echocardiography is indicated for
assessment of cardiac ejection fraction, wall motion
abnormalities, and other critical findings that will direct
acute diagnostic decision making.
INTRODUCTION
Echocardiography has been the “gold standard” for cardiologists for decades. Over the past 20 years, emergency physicians have adopted point-of-care (POC) cardiac ultrasound to
answer specific questions on the management of critical
patients. Assessment for pericardial effusion and for cardiac
activity have traditionally been the principal indications for
emergency physicians, but indications for bedside echocardiography are growing rapidly.1
physicians were found to have a correlation coefficient of
0.86 with cardiologists when assessing ejection fraction.
Cardiologists had a similar coefficient of 0.84 among
themselves.
DIAGNOSIS OF PERICARDIAL EFFUSION
Emergency physicians have proved to be accurate in the diagnosis of pericardial effusion. Previous research has shown
that emergency physicians have a sensitivity of 96%5 to
100%6 as compared with formal overreading by trained
echocardiographers.
HOW TO SCAN/SCANNING PROTOCOLS
PROBE SELECTION
Classic echocardiography requires the use of a phased-array
probe, sometimes referred to as the thoracic probe. These
probes have a small footprint and are ideal for achieving
visualization with a small acoustic window between ribs.
WHAT WE ARE LOOKING FOR
ACOUSTIC WINDOWS
Bedside cardiac ultrasound is typically taught with the use of
three separate acoustic windows and multiple orthogonal
views within the windows. These acoustic windows include
the parasternal, apical, and subcostal. Each window is then
broken down into orthogonal views, including the parasternal
long-axis, parasternal short-axis, apical four-chamber, apical
two-chamber, apical long-axis, subcostal four-chamber, and
subcostal long-axis views.
The initial and best evidence-based indications include applications for tamponade, cardiac arrest, and acute heart failure.
Rapidly developing areas of cardiac ultrasound include evaluation of hypotension, pulmonary embolism (PE), acute
myocardial infarction, diastolic heart failure, and echocardiographically guided resuscitation (Box 5.1).1,2
PROBE ORIENTATION
Echocardiography places the probe marker on the right side
of the ultrasound screen so that when the ultrasound machine
is in the cardiac mode, the right-hand side of the screen indicates the side of the probe with the marker on it (this is
opposite any other scanning mode).
LITERATURE REVIEW
ESTIMATION OF GLOBAL CARDIAC FUNCTION
AND EJECTION FRACTION
Multiple studies have shown the ability of emergency physicians to accurately evaluate cardiac function and ejection
fraction.3,4 When compared with cardiologists, emergency
SPECIFIC VIEWS
Parasternal Long Axis
The parasternal long-axis view seen in Figure 5.1 is obtained
by placing the probe in the third to fourth intercostal space
with the probe marker pointed toward the patient’s right shoulder (Figs. 5.2 and 5.3). The long axis of the heart should be
horizontal on the screen with the apex pointed to the left. If
the apex is pointed up, the probe is too low and should be
43
SECTION I
RESUSCITATION SKILLS AND TECHNIQUES
BOX 5.1 Traditional and Emerging Point-of-Care
Cardiac Ultrasound Indications
Traditional Indications
Tamponade
Cardiac standstill during cardiac arrest
Acute heart failure
Emerging Indications
Echocardiographically guided resuscitation
Undifferentiated hypotension
Pulmonary embolism
Acute myocardial infarction
Diastolic heart failure
Fig. 5.3 Probe orientation for the parasternal long-axis view.
RV
LV
Fig. 5.1 Parasternal long-axis view of a normal-appearing
heart.
Fig. 5.4 Parasternal short-axis diagram. LV, Left ventricle;
RV, right ventricle.
moved up an interspace. This view allows visualization of the
left ventricle, mitral valve, left atrium, right ventricular
outflow tract, aortic valve, and aorta. The descending thoracic
aorta is often visualized posterior to the left ventricle in
transection.
RVOT
LV
Ao
LA
Fig. 5.2 Parasternal long-axis diagram. Ao, Aorta; LA, left
atrium; LV, left ventricle; RVOT, right ventricular outflow tract.
44
Parasternal Short Axis
The parasternal short-axis view is obtained by rotating the
probe 90 degrees from the parasternal long-axis position so
that the probe marker is pointed to the patient’s left shoulder
(Figs. 5.4 and 5.5). The ultrasound beam is now transecting
the heart in its short axis. If the physician tilts the probe so
that it is pointing to the base of the heart, the aortic valve is
visualized along with the “inflow and outflow” of the right
heart. This view includes the right atrium, right ventricular
outflow tract, and pulmonic valve. As the probe is tilted more
apically, the aortic valve is lost and a cross-sectional view of
the mitral valve is obtained (Fig. 5.6). At this point the right
ventricle becomes more apparent and takes a position as a
CHAPTER 5
EMERGENCY CARDIAC ULTRASOUND
Fig. 5.7 Parasternal short-axis view at the level of the
papillary muscles. This is an athletic heart with an enlarged right
ventricle.
Fig. 5.5 Probe orientation for the parasternal short-axis view.
LV
RV
RA
LA
Fig. 5.6 Parasternal short-axis view at the level of the mitral
valve: the “fish mouth” view.
Fig. 5.8 Diagram of the apical four-chamber view. LA, Left
atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
crescentic ventricle to the left and superficial to the mitral
valve and left ventricle. Finally, as the probe is tilted more
toward the apex, the mitral valve is lost and the muscular
portion of the left ventricle is visualized. The posterior medial
and anterior papillary muscles are visualized at this point, and
the circular nature of the left ventricle can be appreciated
(Fig. 5.7).
often impossible. The window is obtained by placing the
probe at the location of maximal impulse with the probe
marker pointed to the left axilla. The probe must be tilted so
that the probe is pointed to the patient’s right shoulder
(Fig. 5.11).
The apical two-chamber view allows further evaluation of
the left ventricle and mitral valve. The left atrial appendage
can sometimes be see on the right side of the screen on the
anterior side of the basal left ventricle.
Apical Four- and Two-Chamber Views
The apical window allows visualization of either all four
chambers (Figs. 5.8 and 5.9) or just two chambers (the left
atrium and ventricle) (Fig. 5.10). The apical windows are difficult to obtain in the emergency setting and often require the
patient to be in the left lateral decubitus position, which is
Subcostal Four-Chamber View
The subcostal four-chamber view (Figs. 5.12 to 5.14) is
obtained by placing the probe just inferior to the xiphoid and
applying pressure downward on the abdomen with the probe
45
SECTION I
RESUSCITATION SKILLS AND TECHNIQUES
Fig. 5.9 Probe orientation for the apical four-chamber view.
Fig. 5.11 Apical four-chamber view. Notice the size of the left
ventricle in comparison with the right ventricle in this normal heart.
Liver
RV
LV
RA
LV
LA
LA
Fig. 5.10 Diagram of the apical two-chamber view. LA, Left
atrium; LV, left ventricle.
horizontal. This view can be performed with either the curvilinear abdominal probe or the phased-array thoracic probe. The
probe marker should be toward the patient’s left in cardiac
mode and toward the patient’s right when using focused abdominal sonography for trauma (FAST) or abdominal protocols.
NORMAL AND ABNORMAL FINDINGS
PERICARDIAL EFFUSION
Evaluation of pericardial effusion is one of the first indications
for cardiac ultrasound.6 Identification of pericardial effusion
(Fig. 5.15) is achieved by visualization of the heart in multiple
views. The subcostal window is the most commonly taught
site because of the FAST examination. An effusion will appear
46
Fig. 5.12 Subcostal four-chamber window. Note the liver
at the top of the ultrasound imaging window. LA, Left atrium;
LV, left ventricle; RA, right atrium; RV, right ventricle.
as an anechoic stripe of fluid surrounding the heart. This stripe
is most commonly located between the right ventricle and the
liver. Ideally, all three acoustic windows should be used when
attempting to rule out pericardial effusion.
The critical complication of pericardial effusion is cardiac
tamponade (Fig. 5.16). Physiologically, cardiac tamponade
occurs when the pressure inside the pericardial sac becomes
elevated above right ventricular diastolic filling pressure. This
leads to decreased filling of the right ventricle in diastole and
reduced preload and cardiac output. Echocardiographic signs
of cardiac tamponade are the presence of right ventricular free
wall collapse as seen in Figure 5.16. Alternatively, a more
sensitive, but less specific finding is the presence of right atrial
collapse during ventricular systole (atrial diastole).
CARDIAC ARREST
POC cardiac echocardiography can be invaluable during
cardiac arrest. Typical uses include evaluation for tamponade,
hypovolemia, and suggestions of PE (clot, right ventricular
CHAPTER 5
Fig. 5.13 Probe orientation for the subcostal four-chamber
window. The probe is placed in the subxiphoid space with the
probe marker oriented to the patient’s left (cardiac mode) or to the
patient’s right (abdomen/focused abdominal sonography for trauma
mode). The apex of the heart should be pointing to the right of the
screen as seen in Figures 5.8 and 5.7.
Fig. 5.14 Subcostal four-chamber window.
dilation); detection of aortic dissection; monitoring for pacer
capture and the adequacy of compressions; and most important, evaluation for cardiac activity in patients with pulseless
electrical activity (PEA) and asystole. Studies have shown
cardiac standstill during arrest to be 100% predictive of mortality.7 Furthermore, cardiac ultrasound has been used in place
of a pulse check in pediatric populations because of the inherent difficulty of finding a pulse.8 Typical algorithms use
cardiac ultrasound to evaluate PEA and asystolic rhythms.9 If
cardiac standstill is present, further resuscitation is futile.7
EMERGENCY CARDIAC ULTRASOUND
Fig. 5.15 Pericardial effusion noted in the parasternal
long-axis view. Notice the location in reference to the descending
thoracic aorta. Pericardial effusions track between the heart and
the descending aorta, whereas pleural effusions can be seen
posterior to the descending aorta.
Fig. 5.16 Pericardial effusion with tamponade. Note the right
ventricular free wall collapse in diastole (arrow).
ACUTE HEART FAILURE
Emergency physicians have been shown to be accurate in
estimating left ventricular ejection fraction (LVEF).3 LVEF is
most easily separated into three categories: reduced, normal,
and hyperdynamic. Although echocardiographers often report
actual percentages, we can think of normal LVEF as 55% to
75%, reduced as less than 55%, and hyperdynamic as greater
than 75%. Some authors add a fourth category in which
severely reduced LVEF is less than 30%. This distinction can
be useful when discussing cardiac function with consultants.
47
SECTION I
RESUSCITATION SKILLS AND TECHNIQUES
The ejection fraction is typically estimated by visual inspection of the “squeeze” of the left ventricle, although it can also
be measured with algorithms in the cardiac package of many
emergency ultrasound machines.
Pitfalls
Emergency cardiac ultrasound involves the use of clear indications and directed ultrasound of the heart to answer specific
questions, as described in the “Introduction.” Apart from these
questions, a cardiologist should be consulted to aid in complex
diagnosis and clinical decision making.
Normal systolic function does not rule out acute heart
failure. Diastolic heart failure can occur in patients with a
normal LVEF.
Diagnosis of cardiac tamponade by echocardiography can
be complicated, and advanced echocardiographic techniques
may be required, including Doppler evaluation. Stable patients
may benefit from evaluation by a trained echocardiographer.
Technically, the bedside sonographer may encounter difficulty obtaining the full series of views as described earlier.
Patient habitus or artifact from the lungs or ribs may present
challenges. Placing the patient on the left side in a left lateral
decubitus position may aid in better viewing the parasternal
and apical windows. This position moves the heart closer to
the anterior chest wall. In the subcostal window, asking the
patient to breathe in deeply may move the heart closer to
the transducer. Additionally, moving the transducer toward the
patient’s right, while still pointing toward the left side of the
chest, may overcome artifact caused by the stomach or bowel
by using the left lobe of the liver as an acoustic window.
PULMONARY EMBOLISM
Although cardiac ultrasound cannot identify a pulmonary
embolus,10 several findings are suggestive of this diagnosis.
Right ventricular dysfunction and dilation are typically visualized in the apical four-chamber window. Right ventricular
dilation has been described in reference to the relative areas
of the right and left ventricles at end-diastole. A right-to-left
ventricular area ratio of greater than 0.66 has been shown to
be 85% specific for PE.11 Another finding is described as
retained apical function in the setting of right ventricular free
wall hypokinesis. This is called the McConnell sign and can
be fairly specific for PE. McConnell et al. described this particular finding as being 94% specific for PE11 (Fig. 5.17). An
additional finding in acute PE is flattening of the interventricular septum. This is seen in the parasternal short-axis view
and is due to either volume or pressure overload of the right
heart (Fig. 5.18).12
VOLUME STATUS
Assessment of the patient’s condition and the presence of
hypervolemia or hypovolemia can be complicated. Through
direct visualization of chamber size and evaluation of
the great vessels, this clinical conundrum can often be
overcome.
Echocardiographic evaluation of volume status starts with
global assessment of the ejection fraction and filling of the
right and left sides of the heart. Reduced filling of both the
right and left heart chambers implies reduced preload and
hypovolemia. Conversely, the presence of dilated right and left
heart chambers with a poor ejection fraction suggests hypervolemia. Finally, a dilated right ventricle with a contracted left
48
ventricle and an elevated LVEF suggests a forward flow
problem of the right heart, such as PE, right-sided myocardial
infarction, or cor pulmonale.
Additionally, a body of research has led to evaluation of the
inferior vena cava as a surrogate marker for central venous
pressure and thus volume status.13 The current recommendations are summarized in Table 5.1. The inferior vena cava
should measured during both inspiration and expiration from
the subcostal long-axis view as seen in Figure 5.19.
Fig. 5.17 McConnell sign. The apical contraction is denoted by
the arrow.
Fig. 5.18 Parasternal short-axis view showing septal
flattening associated with right-sided pressure or volume
overload.
CHAPTER 5
EMERGENCY CARDIAC ULTRASOUND
Fig. 5.19 Subcostal long axis of the inferior vena cava used to estimate central venous pressure.
Table 5.1 IVC Diameters and Respective Collapse
Associated with CVP Estimates
Normal
In between
High
IVC (CM)
COLLAPSE
CVP
<2.1
>50%
3 (0-5)
<2.1/>2.1
<50%/>50%
8 (5-10)
>2.1
<50%
15 (10-20)
Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the emergent
setting: a consensus statement of the American Society of Echocardiography and
the American College of Emergency Physicians. J Am Soc Echocardiogr
2010;23:1225-30.
Mandavia D, Hoffner R, Mahaney K, et al. Bedside echocardiography by emergency
physicians. Ann Emerg Med 2001;38:377-82.
Moore C, Rose GA, Tayal VS, et al. Determination of left ventricular function by
emergency physician echocardiography of hypotensive patients. Acad Emerg Med
2002;9:186-93.
Perera P, Mailhot D, Riley D, et al. The RUSH exam: Rapid Ultrasound in SHock in
the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29-56.
CVP, Central venous pressure; IVC, inferior vena cava.
SUGGESTED READINGS
Blaivas M, Fox J. Outcome in cardiac arrest patients found to have cardiac standstill
on the bedside emergency department echocardiogram. Acad Emerg Med
2001;8:616-21.
REFERENCES
References can be found
www.expertconsult.com.
on
Expert
Consult
@
49
CHAPTER 5
REFERENCES
1. Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the
emergent setting: a consensus statement of the American Society of
Echocardiography and the American College of Emergency Physicians. J Am Soc
Echocardiogr 2010;23:1225-30.
2. Perera P, Mailhot D, Riley D, et al. The RUSH exam: Rapid Ultrasound in SHock
in the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29-56.
3. Moore C, Rose GA, Tayal VS, et al. Determination of left ventricular function by
emergency physician echocardiography of hypotensive patients. Acad Emerg Med
2002;9:186-93.
4. Jones AE, Tayal VS, Sullivan DM, et al. Randomized controlled trial of
immediate vs. delayed goal-directed ultrasound to identify the etiology of
nontraumatic hypotension in emergency department patients. Crit Care Med
2004;32:1703-8.
5. Mandavia D, Hoffner R, Mahaney K, et al. Bedside echocardiography by
emergency physicians. Ann Emerg Med 2001;38:377-82.
6. Plummer D, Brunnette D, Asinger R, et al. Emergency department
echocardiography improves outcome in penetrating cardiac injury. Ann Emerg
Med 1992;21:709-12.
EMERGENCY CARDIAC ULTRASOUND
7. Blaivas M, Fox J. Outcome in cardiac arrest patients found to have cardiac
standstill on the bedside emergency department echocardiogram. Acad Emerg
Med 2001;8:616-21.
8. Tsung JW, Blaivas M. Feasibility of correlating the pulse check with focused
point-of-care echocardiography during pediatric cardiac arrest: a case series.
Resuscitation 2008;77:264-9.
9. Breitkreutz R, Walcher F, Seeger F. Focused echocardiographic evaluation in
resuscitation management: concept of an advanced life support–conformed
algorithm. Crit Care Med 2007;35:S150-61.
10. Ladato J, Ward R, Lang R. Echocardiographic predictors of pulmonary embolism
in patients referred for helical CT. Echocardiography 2008;25:584-90.
11. McConnell MV, Solomon SD, Rayan ME, et al. Regional right ventricular
dysfunction detected by echocardiography in acute pulmonary embolism. Am J
Cardiol 1996;78:469-73.
12. Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic
assessment of the right heart in adults: a report from the American Society of
Echocardiography. J Am Soc Echocardiogr 2010;23:685-713.
13. Jones AE, Tayal VS, Sullivan DM, et al. Randomized controlled trial of
immediate vs. delayed goal-directed ultrasound to identify the etiology of
nontraumatic hypotension in emergency department patients. Crit Care Med
2004;32:1703-8.
49.e1