Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 6
Clinical Examination of the
Cardiovascular System
Introduction
Cattle are phlegmatic animals and rarely undertake
strenuous exercise. As a result, signs of cardiac disease
may not be recognised until the disease is at an
advanced stage. Cardiac anomalies are not uncommon
in calves. Affected calves may show signs of
poor growth and, in advanced cases, heart failure. In
mild cases there may be no external signs and the cardiovascular
abnormality is only detected during a
careful clinical examination. In severe and advanced
cases of heart disease some external signs of illness,
including those of heart failure, may be seen. Animals
may lose condition and may show increased
respiratory effort in an attempt to compensate for
developing hypoxia. Exercise tolerance may be reduced.
Specific signs of heart failure are described
below.
Much of the cardiovascular system is deep within
the body and cannot be directly examined. Abnormalities
of cardiac function may be suspected when
some specific signs are detected during observation
of the patient. Since the cardiovascular and respiratory
systems are physiologically interrelated it
is important to decide whether either one or both
systems are involved in the condition.
Applied anatomy
The heart lies in the anterior part of the thorax between
the 3rd and 6th pair of ribs (Fig. 6.1). The base of
the heart is situated approximately half way up the
thorax. The heart is tilted in a craniocaudal direction
in the thorax. The anterior extremity of the base of the
heart where the great vessels originate is level with
the 3rd rib. The posterior extremity is higher up in the
chest and is level with the 5th rib. The apex of the heart
is low down in the chest and level with the 6th rib.
Visual inspection and physical
examination of the cardiovascular
system
As part of the complete clinical examination the patient
is inspected to see if there are any gross signs of
cardiac disease or cardiac failure. The cardiovascular
system is then carefully and methodically examined
to determine whether any abnormalities are present.
Abnormalities detected during the examination
might be contributing to physical signs already present
or which might cause signs at a later stage of the
disease.
Signs of heart failure
These have been divided into those involving the
right and left side of the heart and relate to the physiological
functions of that part of cardiac activity.
Right-sided heart failure
The signs of right-sided heart failure are associated
with congestion of the peripheral circulation. They
include distension of the jugular veins, brisket and
submandibular oedema, and less commonly distension
of the abdomen by ascites (Fig. 6.2). The hypovolaemia
of a failing peripheral circulation may
result in reduced renal perfusion and lowered urinary
output. Venous congestion in the portal system
may result in enlargement of the liver, a reduction
in hepatic activity and diarrhoea. Poor exercise
tolerance may also be observed, and the animal
may appear dull and depressed. Occasionally in
cardiovascular disease cases, signs of collapse with
temporary loss in consciousness (syncope) may be
seen.
Left-sided heart failure
In left-sided heart failure there is increased
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