Dilated Cardiomyopathy In Cocker Spaniels

Dilated cardiomyopathy (DCM) is a disease affecting the heart muscle and is a congestive heart disease (where the heart does not pump hard enough, causing fluid to back up into the lungs). It is the second most common heart disease in dogs (after mitral valve disease).

With DCM the heart is unable to contract normally & therefore the heart muscle stretches to compensate. DCM affects mainly middle-aged large & giant breed dogs and some spaniels. In most breeds, male dogs are more likely to be affected than females, however this does not appear to be the case with cocker spaniels.

In Cocker Spaniels, the average age at diagnosis is approx. 7 years of age. Males and females are generally affected equally.

What are the signs of cardiomyopathy?

Signs of heart disease can go unnoticed for quite a while, it is not until heart failure develops that owners become aware that their dog is ill, although occasionally a vet may hear an irregular heart beat on a routine examination and this may be the first indication that a dog has heart disease. Symptoms seen are common to all Congestive Heart Failure causes.

Common symptoms are:

• Breathlessness/coughing or fast breathing
• Exercise intolerance
• Lethargy/depression
• Distended abdomen (due to ascites, an accumulation of serous fluid in peritoneal cavity)
• Excessive drinking
• Changes to appetite
• Weight loss
• Weak pulse
• Cold extremities (paws)
• Sudden death

Normal heart

Abnormal heart

Chest/Abdominal X-Ray

The first image below shows a lateral view of a 12 year old cocker spaniels chest. This dog does not have DCM & is healthy in every regard. The image below that shows a 7 year old cocker spaniel with DCM at the time of diagnosis (i.e. pre treatment).

The dog with DCM has an enlarged heart which is pushing up into the thoracic cavity & displacing the trachea (windpipe) (the trachea is kinked due to the heart occupying extra space) and reducing lung space (the triangular area above), the liver is marginally enlarged & oedema is present in the chest/lungs and abdomen which is also visibly swollen. The oedema is shown as white/misty areas.  The lung & abdominal space on the healthy cocker is showing as a black area on the X-ray, the dog with DCM has 'misty' looking lungs due to fluid in the lungs and also has fluid in the abdomen.

Normal abdominal X-Ray

Abnormal heart due to DCM

What is dilated cardiomyopathy?

Cardiomyopathy literally means disease of the heart muscle. With DCM the heart muscle becomes thin and weakened. The heart muscle can be damaged in a number of ways including viral infections and dietary deficiencies of taurine and carnitine (essential amino acid only found in meat protein). The disease is much more common in some breeds than others, therefore genetic factors are probably important. In most cases of DCM there is no apparent cause of the damage to the heart & this is known as "idiopathic cardiomyopathy".

Once the heart muscle is damaged it becomes weak & flabby and it does not contract well. Because heart contractions are weak the heart does not empty with each contraction & the blood supply to the body becomes reduced. DCM eventually results in heart failure with fluid build-up in the lungs (pulmonary oedema), the chest (pleural effusion) and abdomen (ascites).

Causes:

• genetic factors
• metabolic disorders
• inflammations
• nutritional deficiencies
• immunologic abnormalities
• trauma
• toxins
• amino acid deficiency
• taurine deficiency

Can dilated cardiomyopathy be treated?

In almost all cases there is no treatment for the underlying muscle disease as the weakening & thinning of the heart muscle is irreversible. Patients are managed by symptoms with common treatments being diuretics (to increase the flow of urine, which causes the body to get rid of excess water and places less strain on the heart) & vasodilator medication (“Vetmedin” or similar) to relax the smooth muscles that line the walls of blood vessels which causes the blood vessels to increase in diameter & allow blood to flow through more easily. As a result of medication, the heart doesn't need to work as hard to pump blood through them. Long-term treatment includes controlling exercise and administering oral diuretics and vasodilator medications.

Prognosis

The outlook for most dogs with DCM is not very good, however affected cocker spaniels seem to fare better than many other breeds and tend to live longer post diagnosis than many other breeds.

As this is a progressive disease, at some point in time, the body’s ability to compensate is no longer effective. At that stage, dogs go into severe heart failure in what appears to be a matter of hours. Rapid, heavy breathing, a blue tongue, excessive drooling, or collapse may be the first signs that the dog is deteriorating quickly, this will require urgent veterinary attention. It is also possible for some dogs with DCM die suddenly (probably as a result of developing severe cardiac rhythm disturbances).

However the outlook is largely determined by the extent of heart failure and the ability to stabilise the condition with medication. Some dogs, with appropriate management, may live relatively normal lives for years after diagnosis, however studies indicate that most dogs survive around 6 months after diagnosis and approximately one-third of dogs will be alive one year after diagnosis. However, it should be kept in mind that this is a progressive and ultimately terminal disease.