Experiences with Cardiomyopathy
Cardiomyopathy is a common cause of heart disease
in a number of companion animals, including dogs, cats, and as many
owners and breeders know, our little friend, the ferret. The word
cardiomyopathy comes from three Greek words meaning, literally, "a
disease of the heart muscle", and that, unfortunately, sums up much
of what we know of this disease.
The cause of cardiomyopathy in the ferret, as well
as in the dog and the cat, is unknown. In humans, where cardiomyopathy
was first diagnosed and has been studied most extensively, this is
also largely the case, although some types of cardiomyopathy may occur
as a result of pre-existing endocrine diseases, viral disease, toxicities
(including alcoholism), and nutritional deficiency (Robbins, 1989).
There is one cause of cardiomyopathy that has been elucidated in the
cat, and although it has not been definitely linked in the ferret,
may be of importance - taurine deficiency. (This is just another reason
why you should make sure that your ferrets food includes taurine -
make sure to check those labels on the bag of food.)
The hallmark of treatment of this type of heart
disease is two-fold: you must first decrease the amount of fluid
built up in abnormal locations, and second, increase the strength
of contraction of the heart.
Cardiomyopathy in the ferret is an insidious disease
- the majority of the damage to the heart occurs long before the owner
ever realizes that the animal is ill. The general defect in all types
of cardiomyopathy is the same - death of cardiac muscle fibers, which
are then replaced with scar tissue. Scar tissue does not have the
ability to conduct electrical impulse or to contract like heart muscle
fibers can. As more and more myofibers are lost, the heart weakens
and can no longer pump blood efficiently. This results in the two
clinical findings which are the hallmark of diagnosis of heart disease
in the ferret: a) an enlarged heart, and b) a "backing up" of the
blood due to the weakened heart's inability to pump it effectively
(resulting in a syndrome known as "congestive heart failure" - explained
When the blood backs up in the ferret it may go
to a number of places - it may back up into the abdomen, resulting
in a swollen, fluid-filled belly. Additionally, it may back up into
the space around the lungs or into the lungs themselves. If fluid
backs up into the lungs, the ferret may initially show a soft cough.
As the fluid buildup progresses, the cough may worsen, and the owner
will generally notice a sharp decrease in the animal's energy. In
the end stages of the disease, ferrets have marked difficulty in breathing,
often as a combination of the fluid in the lungs and the fluid in
the abdomen (which presses on the diaphragm, impeding the ferrets'
breathing even further). This is what is known as congestive heart
I have also seen cases of a different type of cardiomyopathy
in a handful of ferrets, a type of cardiomyopathy which is also seen
in cats and is known as "hypertrophic cardiomyopathy". In this disease,
there is an overgrowth of fibers in the heart, which encroach upon
the inside diameter of the heart, and in this manner, decrease the
heart's effectiveness in pumping the blood presented to it. The clinical
signs of this type of cardiomyopathy are identical to the congestive
type which has already been discussed.
Diagnosis of the disease is difficult in the early
stages, but becomes progressively easier as the disease goes along.
All of the signs (enlarged heart, fluid in the abdomen or around the
lungs) can be seen on a radiograph (or "x-ray"), and this is the primary
method by which affected animals are diagnosed. Specialized tests,
such as echocardiography, are available at some veterinary hospitals,
and can help pinpoint cases earlier in the disease's progression.
We have discussed that cardiomyopathy is an insidious,
progressive disease; there is no cure for cardiomyopathy, only treatment.
The hallmark of treatment of this type of heart disease is two-fold:
you must first decrease the amount of fluid built up in abnormal locations,
and second, increase the strength of contraction of the heart. Diuretics
are used to mobilize the excess fluid from the abdomen and lungs,
and to keep the blood volume at a level which the weakened heart can
pump it. Digitalis and related drugs help increase the strength of
contraction of the remaining heart muscle to help it pump more effectively.
In early cases, management of fluid volume with diuretics may be the
only treatment necessary, with digitalis and like drugs held in reserve
for the time when the heart becomes weaker.
However, not all animals respond well to treatment.
Dr. James Fox, in his book Biology and Diseases of the Ferret, reports
that even when treated, the clinical course is fairly rapid, and treatment
failures are common. This enforces the need to monitor your pets closely
and bring any suspicions that you may have to the attention of your
1. Robbins SL, Cotran RS and Kumar V. Pathologic Basis
of Disease. W.B. Saunders and Co., Philadelphia, 1989. p. 634-638.
2. Fox, JL. Biology and Diseases of the Ferret. Lea
and Febiger, Philadelphia, 1988, pp 268-269.
3. Jubb, Kennedy, and Palmer. Pathology of Domestic
Animals, vol 3. Academic Press, San Diego, 1985, pp. 26- 29.