Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 6
RA lead
N lead
LA lead
Figure 6.6 Recording a bovine electrocardiograph.The right arm (RA) lead is placed on the neck, the left arm (LA) lead is placed on the chest wall just above the
sternum, and the neutral (N) lead is placed on the withers. See also Fig. 6.7.
enlargement of the heart in cases of chronic cardiac
disease. It is also increased by the presence of a pericardial
effusion. The area of cardiac dullness can be
reduced by emphysema in the lungs. In cattle with
pneumonia, ventral consolidation of the lungs
can make identification of areas of cardiac dullness
difficult.
Electrocardiograph
The ECG is of limited value in cattle but can be used
to confirm abnormalities of rhythm. The extensive
Purkinge network of the bovine heart makes it unlikely
that changes in ventricular size can be inferred
from an ECG recording. A three-lead system is used
(Fig. 6.6) with the right arm (RA) lead attached to the
thoracic wall over the base of the heart. The left arm
(LA) lead is attached over the cardiac apex and the
neutral (N) lead is attached to the skin over the withers.
The P and T waves of the ECG trace are usually
clearly visible as is the QRS complex (Fig. 6.7). In
cases of atrial fibrillation including some animals
with gastrointestinal disturbance, the normal
P–QRS–T sequence in the trace is not visible. Aseries
Figure 6.7 ECG from a normal animal recorded using the lead
configuration shown in Fig. 6.6. Note the positive P and T waves and the
negative QRS complex.
of abnormal F waves replace the P wave, with QRS
complexes appearing at random.
Ultrasonographic (US) evaluation
This is useful to detect abnormalities around the
heart and some details of its internal structure. Evidence
of fluid within the pericardial sac may be seen
as a black non-echogenic area surrounding the heart.
If the contents of the pericardial sac are purulent,
flecks of hyperechogenic material may be seen. The
B-mode scanner can also be used to guide a needle
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