Heart disease is more common in dogs than in any other domestic species. The most common form damages the heart's valves; this occurs primarily in small dogs, from middle age onwards. Congenital heart defects and heart attacks are less common. A wide variety of medications, developed to treat human heart conditions, are used to successfully delay the progression of heart failure.

Heart valve problems
Valvular heart disease is caused when the heart valves do not close properly, causing blood to back up into the lungs or liver (congestion). The earliest signs of heart failure – reduced activity and exercise tolerance - are often mistaken for natural age-related changes. Soon, a dry, non-productive cough develops, initially after exercise and at night. Eventually dogs lose weight, breathe more rapidly, and develop swollen abdomens. Dogs suffering from congestive heart failure are treated with ACE inhibitors such as enalapril, and diuretics such as frusemide are used to eliminate excess fluid.

Dilated cardiomyopathy (DCM)
Cardiomyopathy usually affects dogs under seven years old, and involves dilation or enlargement of the bottom of the heart and thinning of the heart muscle, leading to congestive heart failure. It occurs mostly in medium to large breeds, especially the Doberman, and affects more males than females. Affected dogs lose weight, are lethargic, and tire easily from routine exercise. As heart failure progresses, fluid builds up in the lungs and the belly. Affected individuals are treated for congestive heart failure.

Dirofilaria immitis, spread through mosquito bites and grow in the upper chambers of the heart, causing lack of energy, a moist cough, and heart failure. This parasite is a problem in the Americas, the affected region stretching from the Gulf Coast and Eastern seaboard of North America, especially at low elevations, into Quebec and Ontario. In Europe they occur throughout the Mediterranean region. They are rampant in Australia, where 50% of untreated dogs have heartworm. Your veterinary surgeon will advise you on the use of effective heartworm prevention and treatments during the mosquito season in any region of the world where heartworm is endemic.

Anaemia is a deficiency in red blood cells resulting from a lack of production or loss of blood cells, or their destruction. It causes lethargy and weakness, and can result from obvious external bleeding but also from internal bleeding from ulcers, tumours, parasites, or bowel disease. Some drugs and rodent baits cause also anaemia, and a heavy flea infestation can cause severe anaemia in puppies. The most common form of anaemia diagnosed in clinical practice is called immune-mediated haemolytic anaemia (IMHA). In this condition, the body's immune system turns upon and destroys its own red blood cells.

To treat anaemia, the source of blood loss is found and further loss is controlled. Blood transfusions are given when needed. For IMHA, the outlook is less promising. Even with rapid diagnosis and treatment with high doses of corticosteroids and other immune suppressing drugs, fatal relapses are frustratingly common. 


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