Canine Dilated Cardiomyopathy
Dilated cardiomyopathy (DCM)
is a disease of the heart muscle which causes the
heart to enlarge and not function properly. The
disease usually afflicts larger breeds of dogs such
as the Doberman pinscher, Scottish deerhound, boxer,
Newfoundland, golden retriever, Labrador retriever,
and the Irish wolfhound. However, it can also affect
both the English and American cocker spaniel and
rarely, other small breeds of dogs. The occurrence
of dilated cardiomyopathy increases with age and
typically has an age of onset between 4 and 10 years.
The cause of DCM in dogs is still unknown; however,
many factors suggest a genetic cause.
Dilated cardiomyopathy usually
affects both the left and right sides of the heart
with either side being more severely affected. Typically,
both the ventricle (lower chamber) and the atria
(upper chamber) enlarge and the ventricle loses
its ability to contract and pump blood out to the
body or the lungs. The consequence of the heart
failing in its ability to pump blood can be compared
to a simple mechanical pump. If the sump pump in
your basement fails, water backs up into the basement;
if the left heart fails, fluid backs up into the
lungs and if the right heart fails, fluid backs
up in the abdomen or space surrounding the lungs.
Long term prognosis
for dilated cardiomyopathy varies considerably.
Unfortunately, most dogs with signs of heart failure
at the time of diagnosis die as a result of the
disease within 6 months to two years. Unfortunately,
some dogs, especially certain breeds with a more
severe form of the disease may survive only weeks
to a couple of months.
Treatment of dilated cardiomyopathy
is aimed at both improving the heart's function
and controlling the signs of congestive heart failure.
Drugs such as Lanoxin (Digoxin, Digitalis) are used
to help the heart contract better and to slow the
heart rate down if certain arrhythmias exist. Once
your dog is started on Lanoxin, you will be asked
to watch for signs digoxin toxicity that, although
uncommon, include loss of appetite, vomiting, diarrhea,
and lethargy. These adverse signs can hopefully
be avoided by having a blood test run by your regular
veterinarian 7 to 14 days after the drug is initiated.
To check for appropriate levels of Lanoxin in the
bloodstream, a blood test must be drawn 6 to 8 hours
after your dog’s morning dose of the Lanoxin.
However, if any of these signs do occur, please
call our office or your regular veterinarian. If
these signs are severe, you can stop the Lanoxin
and then call us; however, if the signs are mild,
the ideal situation would be to go to your regular
veterinarian and have a Digoxin level drawn so that
we can be sure that the drug is causing the problems
and the signs are not
related to something else.
Diuretics are also used to
help both control and prevent accumulation of fluid
in or around the lungs. Lasix (Furosemide) is usually
the drug of choice. Potential side effects of diuretic
use include increased thirst and potentially increased
urination. Another essential drug that is used in
the treatment of dilated cardiomyopathy is termed
a balanced vasodilator. This helps the heart pump
more effectively against the pressures of the arteries
and veins. Examples of this drug include Vasotec,
Enacard, Zestril, Prinavil, and Lotensin. These
drugs are usually started gradually with a low dose
and then building up to your dog's required dosage.
These drugs can occasionally interact with the kidneys.
For this reason, you will be asked to see your regular
veterinarian in 7 to 10 days, in 4 weeks, and then
every three months to have a chemistry blood panel
checked to assure that kidney function is preserved.
Other drugs utilized in the
treatment of dilated cardiomyopathy are aimed at
controlling cardiac arrhythmias (electrical disturbances
in the heart). Arrhythmias can be very problematic
in some cases of DCM and can even be life threatening.
Certain breeds are more predisposed to this additional
problem. If possible, it is a good idea to buy an
inexpensive stethoscope to monitor your dog's heart
rate and rhythm. Keep a journal of these records
and if you are seeing a progressive increase or
decrease in your dog's heart rate or hear an irregular
heartbeat, please call our office.
It is also important for you
to monitor your dog's overall attitude and outward
signs. If you notice any heavy/labored breathing,
coughing, fainting spells, restlessness, or profound
lethargy, please call us or see your regular veterinarian
as soon as possible.