Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

Clinical Examination of the Cardiovascular System
Body wall
Tricuspid
valve
Pericardial effusion
Wall of left ventricle
Figure 6.8 Diagram of an ultrasonographic scan of an animal suffering from pericarditis showing the presence of a pericardial effusion.
into the pericardial sac to collect a sample of fluid for
analysis. A3.5 or 5MHz probe is suitable for examining
the heart in calves. For larger cattle, a 2.25 or
3.0 MHz probe, which gives greater penetration, is
needed. Access for ultrasonography to the bovine
heart may be difficult since in the lower thorax the
ribs are wide and the space between them is very narrow.
Quite good visualisation of the cardiac chambers
can be achieved in calves using a basic linear
array scanner. Such scanners can also be used to detect
the presence and character of pericardial fluid
(Fig. 6.8). Sophisticated but expensive scanners such
as the Doppler flow sector scanner produce more information,
including the direction and pressure of
blood flow. This information is particularly helpful
in cases of congenital cardiac abnormality.
Radiography
This is of limited value in assessing bovine cardiac
morphology. The size and mass of the bovine heart
prevent clear demonstration of the internal divisions
of the heart. An outline of the heart can be delineated
radiographically giving an approximate measure of
size. Radio-opaque foreign bodies (such as wires)
may be detected as they pass through the diaphragm
from the reticulum to the pericardium.
Pericardiocentesis
This technique is used to collect and assess pericardial
fluid. A 12 cm spinal needle of size 16 BWG
(1.65 mm) is used. The needle is inserted through the
chest wall into the pericardial sac and fluid is allowed
to flow or is aspirated using a syringe. Local anaesthetic
is injected into the skin and muscle layers of
the space between the 5th and 6th ribs. The area is
prepared aseptically and the needle with syringe
attached is advanced carefully towards the heart.
Fluid, which may be very foul smelling if infection
is present, is aspirated for cytology, culture and
drainage purposes. If ultrasonographic equipment is
available the needle may be directed visually. If such
equipment is not available care must be taken to
avoid penetrating the myocardium with the needle
(Fig. 6.9).
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