DILATED CARDIOMYOPATHY
Description
Dilated cardiomyopathy is a common form of cardiomyopathy.
Breed Occurrence
Dilated cardiomyopathy is most commonly seen in large breed dogs including
the Doberman Pinscher, Cocker Spaniel, Springer Spaniel, Boxer, Irish Setter,
German Shepherd Dog, Great Dane, St Bernard and Irish Wolfhound. It is usually
seen in young adult male dogs (mean age of presentation to a veterinarian
4-6 years of age).
It is also seen in young to middle-aged cats (mean age reported to be
7.5 years) and, although all breeds can be affected, there is a higher incidence
in the Siamese, Abyssinian and Burmese breeds. In cats this form of heart
muscle disease was associated with taurine deficiency but this is now rare.
Age prevalence
In dogs dilated cardiomyopathy can occur at any age, but in most breeds
of dog dilated cardiomyopathy occurs at a mean age of 4-6.5 years, whereas
in the Boxer it occurs slightly later (at an average age of 8 years).
In cats dilated cardiomyopathy can occur at any age with a mean age of
onset of about 7.5 years.
Sex prevalence
Males are usually affected more frequently than females with this disease,
except for Boxers and English Cocker Spaniels in which breeds studies suggest
both sexes are equally affected.
Signs
In dogs the condition can be present for a long time with no obvious symptoms,
then the clinical signs often start suddenly and include the typical signs
of heart failure including both forward and backward failure. Commonly seen
signs include difficulty breathing (called dyspnoea), a cough, feinting,
exercise intolerance and a swollen abdomen. Affected dogs often have reduced
appetite and weight loss.
Radiography
On plain radiographs all forms of dilated cardiomyopathy may show as bilateral
enlargement of the heart (called cardiomegaly) . In some breeds there may
be evidence of fluid accumulation in the lungs (called pulmonary oedema)
- Doberman and English Cocker Spaniel and cats; or free fluid in the chest
(called pleural effusion) - Dobermans.
Ultrasound (called echocardiography)
Moving (M-mode) echocardiography is the best diagnostic tool to use to
confirm the diagnosis of dilated cardiomyopathy because it clearly shows
dilation of the heart chambers with severely reduced shortening fraction
of the heart wall when the heart muscle contracts.
Treatment
Unless a specific underlying cause can be determined e.g. taurine deficiency,
L-carnitine deficiency, treatment can only be symptomatic and are the same
as those commonly used to treat heart failure.
Prognosis
The prognosis is always guarded to poor at the outset with the average
survival time being 6 months and 80% of dogs with atrial fibrillation die
in this period. Dobermans often die within days or weeks and rarely survive
for more than a year, whereas some breeds (including German Shepherds and
Great Danes) often respond well and can survive more than 2 years.
The prognosis is good for dilated cardiomyopathy associated with taurine
deficiency in cats, as correction of the nutritional deficiency effectively
reverses the disease.
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HYPERTROPHIC
CARDIOMYOPATHY
Description
Hypertrophic cardiomyopathy is one of several forms of heart muscle
disease which commonly affects cats and is rarely diagnosed in dogs.
The disease is characterised by gross thickening of the muscle in the walls
of the heart which makes the walls stiff and less compliant. This results
in poor filling of the heart chambers with blood during the diastolic phase
of contraction, and inadequate output of blood during systole. The clinical
signs of this condition are those of heart failure.
Cause
The cause is unknown.
Breed Occurrence
The condition is rare in dogs but the German Shepherd Dog is cited as being
the breed most likely to present with hypertrophic cardiomyopathy. In cats
no particular breed or group are affected.
Age
Hypertrophic cardiomyopathy can occur at any age in cats (range 5 months-14
years)
Signs
Sudden death without prior warning can occur. Some cases present with "forward
failure" of the heart and exhibit exercise intolerance. Cats are often off
their food (called anorexia) and lethargic with increased respiratory rate
(tachypnoea) difficulty breathing (dyspnoea) and in some cats feinting and
lameness due to thromboembolism).
x -ray
Chest X-rays may not show much heart enlargement, though left-sided
enlargement is often seen. Evidence of fluid in the lung tissue (pulmonary
oedema) tends to be diffuse in cats, and more localised in dogs. Sometimes
free thoracic fluid (pleural effusion) masks the presence of oedema.
Ultrasound (Echocardiography)
Echocardiography clearly shows a small chamber to the left ventricle with
thick muscular walls. Often can detect atrial enlargement and occasionally
see thrombi when they are present. M-mode examination of the left ventricle
also demonstrates the thickened free muscular wall and septum.
Treatment
The same as for the treatment of heart failure.
Prognosis
If the patient has mild to moderate severity of the disease a good response
to treatment can be expected, but dysrhythmias and sudden death can still
occur and in cats which develop thromboembolism the prognosis is much worse.