Canine cardiomyopathy is a diverse group of heart disorders. Dilated cardiomyopathy (DCM) is one of the most common acquired heart diseases of middle-aged dogs. DCM has been recognized in many breeds but seems to be more prevalent in the English Cocker Spaniel, Doberman Pinscher, Boxer, Newfoundland, and Irish Wolfhound. Dogs with idiopathic dilated cardiomyopathies are prone to life-threatening arrhythmias and sudden death. The disease is characterized by weakening of the heart muscle leading to impaired functioning of the heart, lungs, liver, and other body systems.
There are two distinct forms of canine DCM that differ in the structure of heart muscle tissues. The first type is fatty infiltration-degenerative type (previously called "Boxer cardiomyopathy" and now seen in Boxers and Doberman Pinschers), in which the muscle fibers degenerate and are replaced by fatty deposits. The second type is attenuated wavy fiber type, which is seen in giant, large-, and medium-sized breeds, including some Boxers and Doberman Pinschers, and is considered more prevalent. Canine DCM has been suspected to be an inherited disease because of its prevalence in certain breeds and in specific families of dogs. An autosomal dominant mode of transmission has been reported in the Irish Wolfhound, Newfoundland, and Doberman Pinscher. In the juvenile Portuguese Water Dog, an autosomal recessive transmission has been documented. Several causes of DCM have been proposed, including genetic factors, nutritional deficiencies (carnitine or taurine), hormonal and metabolic disorders (hypothyroidism, diabetes mellitus, and pheochromocytoma), immunologic abnormalities, infectious diseases, and drug-, toxin-induced. It is clear that dogs, like humans, have a prolonged sign-free phase of the disease extending over years. Prospective screening of dogs from lines with familial prevalence of DCM may identify dogs with pre-clinical DCM. Dogs with other cardiac abnormalities or arrhythmias may also be identified.
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Signs may include difficulty breathing, cough, unwillingness to move, depression, exercise intolerance, loss of appetite, fainting, weight loss, increased thirst and pot-belly appearance. Diagnosis is based on findings on echocardiographic and Doppler examinations. Dogs with DCM and heart failure benefit from medications affecting the contraction of the heart muscle. Ideally, this would be with pimobendan that has been shown to increase survival. Additional medications for heart failure, such as ACE inhibitors and diuretics are used as needed. Nonspecific treatments, including taurine, are administered to dogs with low levels of this nutrient. Although canine dilated cardiomyopathy is generally progressive and fatal, there have been a few cases of several Golden Retrievers with reversible taurine-deficient dilated cardiomyopathy. Significant improvements were recorded within 3 to 6 months of starting taurine supplementation. The dogs regained substantial systolic function, and four were weaned off all medications except taurine. Supplementation with fatty acids may be considered for patients suffering from malnutrition. Survival times vary from days to several years.
- A. Tidholm and L. Jönsson Albano Animal Hospital of Stockholm. Histologic Characterization of Canine Dilated Cardiomyopathy
- Belanger MC, Ouellet M, Queney G, Moreau M. Taurine-deficient dilated cardiomyopathy in a family of golden retrievers.
- Technique provides new look on response of diseased canine heart (www.news.uiuc.edu)
- Stephen J. Ettinger, DVM, DACVIM and Edward C. Feldman, DVM, DACVIM. Textbook of Veterinary Internal Medicine