Dilated cardiomyopathy (large heart in dogs), as its name suggests, is a pathology that causes dilation of the cardiac chambers (atria and ventricles). It is a serious and progressive disease in which the muscle fibers of the heart begin to degenerate and lose their function. Consequently, both the contractile capacity of the heart and the filling of the ventricles are affected. This dysfunction often leads to the development of Congestive Heart Failure (CHF).
Keep reading this article on our site to learn more about dilated cardiomyopathy in dogs, its clinical signs, diagnosis and treatment.
What is canine dilated cardiomyopathy?
Dilated cardiomyopathy (large heart in dogs) is considered an idiopathic disease, that is, of unknown origin. However, the greater predisposition to the disease of some breeds, as well as the detection of specific genetic mutations in some of these breeds, suggests that the pathology has a genetic basis.
This pathology accounts for 0.5% of cardiovascular diseases, and is therefore much less frequent than valvular pathologies. However, its evolution is much faster and more serious than that of valve disease, which is why it is essential to make an early diagnosis of canine dilated cardiomyopathy.
There is a greater predisposition to the disease in large or giant breed dogs, such as the Doberman, Boxer, Mastiff, Irish Wolfhound or Pyrenees mountain, among others. The prevalence of the disease increases with age, with the average age of dogs affected by canine dilated cardiomyopathy oscillating between 4 and 8 years old Also, males seem to get sick more often than females.
Clinical signs of dilated cardiomyopathy in dogs
As we have already mentioned, canine dilated cardiomyopathy (large heart in dogs) develops progressively. Initially, an “asymptomatic or preclinical phase”occurs in which the disease is present but no clinical signs are observed. This is because the body sets in motion a series of compensatory mechanisms that try to prevent the onset of heart failure. Once these compensatory mechanisms are overcome, the “clinical phase” of the disease begins, in which the animal develops clinical signs of heart failure, such as:
- Syncopes: these are episodes that occur with sudden loss of consciousness, followed by complete, spontaneous and usually sudden recovery. It is caused by a transient decrease in blood flow to the brain.
- Signs of left heart failure: mainly respiratory signs such as cough, tachypnea (increased respiratory rate), dyspnea (breathing difficulty) and orthopnea (respiratory difficulty in which the animal acquires postures that facilitate breathing such as stretched neck, head up or more open forelimbs).
- Signs of right heart failure: jugular distention, positive jugular pulse and ascites.
- Weightloss.
- Weakness, lethargy and exercise intolerance.
Diagnosis of dilated cardiomyopathy in dogs
Performing an early diagnosis is of vital importance, given that the survival period of the animal will depend on the moment in which the diagnosis is made. diagnosis, specifically the degree of heart failure. However, diagnosing the disease at an early stage is a complicated task because the patient does not present clinical signs at the beginning of the disease. For this reason, in predisposed breeds it is advisable to carry out screening tests on an annual basis to detect signs of dilatation in animals that are still asymptomatic. In this way, treatment can be established early and thus increase the probability of survival of the animal.
The diagnosis of dilated cardiomyopathy (large heart in dogs) will be based on the following points:
- Clinical history and anamnesis: your veterinarian will ask you about the presence of any of the clinical signs described above, which will will allow dilated cardiomyopathy to be considered as a possible differential diagnosis.
- General examination: your veterinarian will perform a general examination of your pet, paying special attention to thecardiopulmonary auscultation : if it detects arrhythmias or murmurs, it will carry out additional tests or refer you to a cardiology specialist to perform them.
- Complementary tests: including an electrocardiogram, a chest X-ray and an echocardiogram. In the electrocardiogram, alterations such as premature complexes or ventricular extrasystoles and atrial fibrillation can be found. Chest radiography will show cardiomegaly (enlarged heart) and, depending on whether left or right heart failure predominates, pulmonary edema, pleural effusion, dilatation of the caudal vena cava, hepatosplenomegaly, and ascites may be seen. Echocardiography will show, among other things, ventricular dilatation with thinning of the heart walls.
As we have already mentioned, dilated cardiomyopathy is an idiopathic disease. However, it must be taken into account that there are multiple processes that, in a secondary way, are causes of enlarged heart in dogs, without being in themselves a dilated cardiomyopathy. Therefore, in order to reach a definitive diagnosis of idiopathic dilated cardiomyopathy, all those processes that secondarily cause myocardial dilation must be ruled out beforehand. These processes include:
- Nutritional deficiencies: mainly taurine and L-carnitine deficiencies. Vegan and grain-free diets seem to be associated with cardiac dilation.
- Infectious diseases: viruses such as parvovirus, herpesvirus, adenovirus and distemper virus, bacteria such as rickettsiae and spirochetes, parasites such as Toxoplasma, Toxocara and Trypanosoma, and fungi.
- Endocrine diseases: such as hypothyroidism, diabetes mellitus and pheochromocytoma (adrenal medullary tumor that produces excess catecholamines).
- Biochemical alterations: such as altered activity and concentration of mitochondrial enzymes, altered calcium homeostasis or altered calcium receptors membrane.
- Cardiotoxic agents (drugs and toxicants): including chemotherapy drugs such as doxorubicin, histamine, catecholamines, methylxanthines, vitamin D, ethyl alcohol, cob alt and lead.
In the event that the complementary tests confirm the dilation of the cardiac chambers and that any process that causes a dilation of the heart has been ruled out, your veterinarian will issue a diagnosis ofidiopathic dilated cardiomyopathy.
Treatment of dilated cardiomyopathy in dogs
For the treatment of dilated cardiomyopathy it is necessary to differentiate whether it is an acute or chronic process.
The acute symptoms are considered a medical emergency, requiring immediate treatment and hospitalization. The therapeutic goals in cases of acute heart failure are to optimize cardiac output, improve oxygenation, and reduce pulmonary edema. To do this, the treatment must include:
- Drugs positive inotropes such as dobutamine, to increase cardiac contractility.
- Oxygen therapy, to improve oxygenation.
- Diuretics such as furosemide and vasodilators such as sodium nitroprusside, to reduce pulmonary venous pressure and thus reduce pulmonary edema.
- Pleurocentesis and pleural drainage, if there is pleural effusion.
- Drugs antiarrhythmics, such as digoxin and/or diltiazem, in case of serious cardiac arrhythmias.
The treatment of chronic conditions aims to improve the animal's quality of life and prolong its survival. Outpatient treatment of these patients should include:
- Pimobendan: it is the only positive inotrope that has no chronotropic effects, that is, it increases contractility without affecting the heart rate. In addition, it has vasodilator properties.
- Diuretics:such as furosemide.
- Mixed vasodilators: such as ACE inhibitors.
- Drugs antiarrhythmics: such as digoxin and/or diltiazem, in case of serious cardiac arrhythmias.
- Diet low in sodium and chlorine: supplementation with taurine and L-carnitine, omega-3, coenzyme Q10 may also be recommended and vitamin E.
In short, dilated cardiomyopathy is a serious, fatal disease for which there is no curative treatment. However, an early diagnosis of the disease, as well as the establishment of adequate pharmacological treatment, will be decisive in delaying the appearance of serious clinical signs and increasing the life expectancy of affected patients.
