show the size of the cardiac silhouette which may or may not be the
same size as the heart itself. (Certain conditions that cause a build
up of fluid around the heart could make the heart appear larger than
it actually is.) Usually the silhouette is equal to the size of the
heart so that chest X-rays give us an impression of heart size. We can
also see the diameter of the trachea (windpiipe) and the bronchi, the
blood vessels in the lungs, whether the lungs are clear or have some
sort of infiltrate (fluid, pus, blood, etc.) and whether the infiltrate
appears to be in the alveoli (air sacs) of the lungs or in the spaces
between. We can sometimes see evidence of a mass (like a tumor) in the
lungs or on the heart. For evaluating heart disease, these are not very
accurate since enlargement of the heart usually comes later in heart
disease after symptoms have begun.
is a measurement of the electrical activity of the heart. When leads
from the ECG machine are attached to different areas of the animal the
electrical impulses are measured across those leads (one is a positive
electrode and one negative). When an electrical impulse from the heart
moves toward the positive lead, there is a positive (upward) blip made
on the ECG screen or paper, while an impulse moving away from the positive
lead produces the negative blip. The ECG can be valuable in diagnosing
arrythmias if they are occurring continuously or with very high frequency
(several per minute). If the arrythmias are sporadic, they are of use
only if the arrythmia is occurring at the time of the exam. It is true
that significant cardiac disease may be present and produce minor or
NO abnormalities on ECG. The ECG does not show how the heart is functioning
mechanically, only how the electrical impulses are occurring.
are made by use of Ultrasound equipment. The echo does allow one to
see the mechanical function of the heart. You can see the heart contracting,
the valves opening and closing and how they move, whether there are
any irregularities (vegetative growths) on the valves. You can measure
the chamber diameters when the heart is contracting and when it is relaxed.
You can measure the thickness of the muscular walls of the chambers.
Doppler echocardiography adds a sound component to the above and allows
one to hear the turbulence that is known as a heart murmur in an amplified
also adds color to the image and allows visualization of blood flow
through the heart and major vessels.
is a backpack type recording device that enables a prolonged sampling
of an ECG. This piece of equipment is the most useful in detecting intermittant
arrythmias due to the long sample time (24 hours or longer). Since most
cases of boxer cardiomyopathy begin in the early phase as a minor arrythmia,
this is the most useful piece of equipment we have available currently
to "screen" boxers for arrythmias.
This is a device that can be worn for prolonged periods of time and
activated only if the patient has an episode. It is a continuous loop
type recorder, so that when activated by the push of a button, it saves
the ECG pattern for the last several minutes. This would be useful for
a dog that is having fainting spells (syncope) but who has normal ECGs
when examined at the veterinary office. The owner would be instructed
to push the activation button when the animal had the next episode.
One could then determine if the cause of fainting was of cardiac origin
(like an arrythmia).