Page 148 - Basic Monitoring in Canine and Feline Emergency Patients

4. Assess for the step sign. The step sign is used to view’. At this level the TFAST operator can
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describe a discontinuity in the pulmonary–pleural subjectively assess contractility of the ventricle
VetBooks.ir line, usually associated with a thoracic wall or pleu- while also looking for pericardial effusion. With
advanced training the operator can also meas-
ral space discontinuity (Fig. 7.6C). Conditions that
lead to the step sign include rib fractures, pulmonary
diastole, measure left ventricular wall thickness,
masses, pleural effusion, a diaphragmatic hernia, a ure ventricular volumes at the end of systole and
mediastinal mass, and potentially left-sided cardio- and calculate fractional shortening. The details
megaly. The presence of a step sign warrants addi- of measuring and performing these calculations
tional imaging such as thoracic radiography. Do is beyond the scope of this chapter. See Further
not look for the step sign caudal to the CTS as the Reading section for detail regarding focused
normal lung-diaphragm-liver interface can create echocardiogram assessment.
what looks like a step sign. 3. The operator can assess the left atrium:aorta
5. Repeat steps 1-4 on the right hemithorax. (LA:Ao) ratio. The LA:Ao ratio is performed to
gauge suspicion for left-sided heart failure in the
dyspneic patient. The LA:Ao ratio is performed
Pericardial sites using the US transducer probe with the indica-
tor/notch facing toward the elbow. Typically, the
The pericardial sites (PCS) are used to look for probe is moved up one intercostal space or lightly
pericardial effusion and, with training, can be util- fanned cranially to obtain a right parasternal api-
ized to assess left-sided heart volume status and cal transverse (short axis) view of the heart base. In
systolic contractility. Both left and right PCS should this view the US TFAST operator should be able
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be assessed during a TFAST examination. to see the aorta, left atrium and right ventricular
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The PCS exam is performed as follows:
outflow tract/pulmonary artery (Fig. 7.7B). The
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1. The TFAST operator should palpate the heart’s aorta at the level of the aortic valve will appear as
point of maximum intensity and place the probe at the classic ‘Mercedes Benz’ view. At this level, the
that site. If the point of maximum intensity cannot operator can assess the LA:Ao ratio by measuring
be identified, place the transducer probe on the con- the diameter of the chambers. An LA:Ao ratio < 1.5
tralateral gravity-dependent side between intercos- is normal. Typically cats with heart failure have sig-
tal spaces three through five (Fig. 7.3). When trying nificantly increased LA:Ao ratios of >2.0.
to find the location of the heart quickly, the author
moves the elbow to the level of the costochondral
junction and puts the transducer probe at this loca- Diaphragmaticohepatic view
tion. Place the US probe with the indicator/notch The DH view is the final site to assess for pleural
facing dorsally toward the spine. Slide the trans- and pericardial effusion during a TFAST (see Fig.
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ducer slightly dorsally and adjust the depth of the 7.3). This view allows imaging of the pleural and
transducer to focus the heart within the distal/bot- pericardial sites with less air interference and can
tom third of the US viewing window. Fan the probe evaluate the diaphragm for herniation. See the pre-
slightly to obtain both a four-chamber (Fig. 7.7A) vious AFAST section of this chapter for a descrip-
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and five-chamber view (right parasternal long-axis tion on how to acquire images in this view. When
view) of the heart while evaluating for pericardial an animal is in respiratory distress, pressing the US
effusion. The chamber sizes can also be subjectively probe into the DH site may be uncomfortable or
observed in this view. In health, the left ventricle stressful. Moving the US transducer probe from the
should be approximately three to four times the subxiphoid location to a location slightly pericos-
size of the right ventricle, the atria should be sym- tally will allow for easier breathing while still
metrical, and the interventricular septum should be obtaining the same information.
straight. See Further Reading section for more infor-
mation on focused echocardiogram assessment.
2. Rotate the transducer until the indicator/ Other information obtained during TFAST 3
notch is perpendicular to the elbow. This should
reveal the transverse (right parasternal short axis) lung point (pneumothorax) If present, the sever-
view of the heart. When at the level of the mitral ity of a pneumothorax is gauged by determining
valve, this view will reveal the classic ‘mushroom the lung point. The lung point is the position along

140 D.M. Hundley