A healthy
heart is essential to successful performance for any athlete and this
is certainly true of canine competitors. Heart disease in dogs may
be present since birth (congenital conditions) or may be acquired
later in life. Dogs can develop abnormalities of the heart valves
or heart muscle, as well as structural deformities. Clinical signs
of heart disease in dogs include exercise intolerance, fatigue, shortness
of breath, fainting, discoloration of the gums, coughing and restlessness,
particularly at night. Upon physical examination, a veterinarian may
detect abnormalities such as a heart murmur, an abnormal heart rhythm,
or a rapid or slow heart rate. If heart disease is suspected, a consultation
with a veterinary cardiologist is strongly recommended in order to
further define the extent of the problem. This is particularly important
with working dogs and those that are actively involved in competition.
A thorough cardiac evaluation is also recommended for young dogs that
are about to enter into competition for the first time.
Cardiac
evaluation begins with a complete physical examination and auscultation
of the heart with a stethoscope. Further assessment is performed
using a series of specialized diagnostic tests. These include thoracic
radiographs (chest x-rays), an electrocardiogram (ECG), and an ultrasound
examination of the heart, referred to as echocardiography.
These tests provide different pieces of information about the overall
health of a dog's heart.
Chest
x-rays provide direct information regarding the size of the heart
and the condition of the lungs. The larger vessels entering and
leaving the heart can also be evaluated. In cases of heart failure,
fluid accumulation can be detected. When x-rays are repeated over
a period of time, they can help judge the effectiveness of treatment.
An
electrocardiogram is a test used to record the electrical activity
of the heart and to detect abnormal heart rhythms called arrhythmias.
The ECG can also provide information regarding enlargement of specific
chambers of the heart and the position of the heart in the chest
cavity.
Echocardiography
is a highly specialized, non-invasive test that allows the veterinary
cardiologist to "see" inside the heart using a form of sonogram.
An ultrasound probe is placed on the chest and sound waves are used
to assess heart structure, chamber size, and heart valves. The ultrasound
exam allows for evaluation of functional abnormalities such as weak
heart muscle contractions or incompetent heart valves. A specialized
test called "color flow Doppler" provides greater detail about the
blood flow through the heart. This test is discussed in more detail
elsewhere in this issue (see page 5).
When
these tests are performed on a canine athlete, they provide complete
information regarding the dog's heart. If no abnormalities are
detected, the dog is cleared of any limitations due to cardiac disease.
In cases where one or several tests are abnormal, the veterinary
cardiologist will interpret the information and formulate a treatment
plan.