Canine Dilated Cardiomyopathy

As the words describe, this disease in dogs results in enlargement of the heart muscle and is usually a secondary cause of heart failure.

This dilation is of the left ventricle and is a result of a cardiac pump failure. This disease affects mainly large breeds of dogs between three and eight years of age. The Great Dane, Irish wolfhounds, Saint Bernard, German Shepherds, Mastiffs and Newfoundland are the breeds commonly affected. The disease affects males more than females. Since it occurs in large fast-growing breeds, hereditary and nutritional factors should be considered.

Dilated cardiomyopathy is occasionally associated with other diseases, especially the gastric dilatation/torsion complex seen in large/giant breeds.

No specific cause of the severe myocardial damage has been confirmed but it is most likely due to a variety of causes such as viral infections, chemical agents and immunological abnormalities.

Most dogs with dilated cardiomyopathy are examined for various degrees of right and left-sided heart failure. The history usually includes weight loss, general debility, weakness and abdominal distension over a one- to three- week period. Clinically there is coughing, dyspnoea ( short of breath), syncope ( feinting ), anorexia and ascites ( fluid in the abdomen ). A rapid irregular heart beat may be easily palpated over the left ventral side of the chest, and auscultation may reveal systolic murmurs of low to moderate intensity over the left chest as well as a galloping rhythms.

Diagnosis is based on the history of acute onset of all the clinical signs. Once a provisional diagnosis has been made then an electrocardiograph ( ECG) and chest radiographs will help to confirm the diagnosis. The ECG usually shows atrial fibrillation and left ventricular enlargement. All the associated ECG signs of ventricular enlargement help to confirm the diagnosis. Thoracic radiographs show moderate to severe enlargement of all cardiac chambers. The lungs also show congestion and oedema as well. A pleural effusion and ascites are also seen, and help to confirm the diagnosis.

The prognosis of a dog diagnosed with dilated cardiomyopathy is very poor with the average survival time being between 6 to 12 months after the onset of clinical signs.

Treatment is aimed at :

1. strengthening the function of the heart as a pump

2. sparing the heart by reducing the workload

3. preventing secondary damage to the heart muscle and other organs

4. promote recovery of the heart muscle.

Treatment for cardiac failure associated with dilated cardiomyopathy should include rest, a low sodium diet, slowing of the heart rate and diuretics to reduce blood pressures and workload of the heart.