Nutrition of dogs with heart disease

Heart disease is a common health problem in dogs and is the second most common cause of death after cancer. It is reported in the literature that approximately 10-11% of dogs suffer from heart disease. Chronic valvular heart disease (CVD) or dilated cardiomyopathy (DCM) is most common in these dogs. Chronic valvular disease is particularly prevalent in small breeds of dogs such as the King Charles Spaniel, poodle, dachshund or small schnauzer, whereas DCM is found mainly in large breeds of dogs, most commonly the Irish Wolfhound, Great Dane, St Bernard, Newfoundland, Boxer and Doberman. Heart disease results in chronic heart failure, a condition in which the heart is no longer able to perform its functions adequately, supplying oxygen and nutrients to the tissues and removing waste products and carbon dioxide. Heart failure is manifested by weakness, reduced ability to tolerate exertion, shortness of breath, coughing, and possibly brief loss of consciousness. There may also be a build-up of fluid in the abdominal cavity, which manifests as an increase in abdominal volume with overall poorer nutritional status. Dogs suffering from chronic heart failure often have a reduced appetite (anorexia) and poor nutritional condition accompanied by significant loss of muscle mass (cachexia). This condition is particularly dangerous and is associated with a shorter survival time. Cachexia with loss of muscle mass has been found in less than 50% of dogs with chronic heart failure. Unlike in humans, obesity is not usually the cause of heart disease in dogs, but it can worsen its course and prognosis. The main goal of nutrition for dogs with cardiac cachexia is to ensure adequate energy and quality protein in the diet. The food must be highly digestible, palatable and energy-dense, with a sufficient content of complete protein. Palatability can be improved by warming the feed to body temperature or by adding flavour enhancers (e.g. yoghurt, meat broth, maple syrup or honey). Feeding a smaller ration several times a day or switching to a different type of food, e.g. from a dry diet to a canned or balanced homemade diet, may also help. Supplementing with fish oil high in omega-3 fatty acids can reduce the production of pro-inflammatory substances in dogs, improving their nutritional status while contributing to a more palatable food. If, on the other hand, the dog is obese, it should be fed a balanced, low-calorie diet with reduced fat and digestible carbohydrates and sufficient high-quality protein. Obesity causes serious changes that can complicate the course and treatment of heart disease, so an effective weight reduction programme must be initiated. Protein is of particular importance in reduction diets. Intake of a low-calorie diet with a higher ratio of protein to energy significantly increases body fat loss and reduces muscle loss. In addition, protein consumption also increases energy expenditure more than carbohydrate or fat consumption. Nutrition plays an important role in dogs with heart disease. A properly adjusted diet can help slow the progression of the disease and improve the patient's quality of life. Reduced protein was previously recommended, but it is now clear that there is no justification for this measure. Dogs with heart failure, on the other hand, need plenty of good quality and easily digestible protein because they are at risk of cachexia and muscle loss. Unless the dog is also suffering from severe kidney disease, it should be fed a diet containing high quality protein that will fully cover its need for rescue. The crude protein content should not be less than 18 % on a dry matter basis; at least around 20 % is preferable. Protein of animal origin should predominate in the composition, containing all essential amino acids in the required amounts and proportions. Of the minerals, the most important are sodium (together with chloride in the form of table salt), magnesium and potassium. In dogs with heart failure, sodium excretion by the kidneys is reduced and sodium and water accumulate in the body. Healthy animals can easily excrete excess sodium in the urine, whereas animals with heart disease have limited excretion. Therefore, the sodium (salt) content of the diet for cardiac patients should be reduced. Currently, only moderate sodium restriction is recommended for early stage heart disease. Even for patients treated with ACE inhibitors and certain types of diuretics, a diet with a significantly reduced sodium content is not recommended, as these drugs cause increased sodium loss. In the early stages of heart disease, a diet with significant sodium restriction is not beneficial and may have adverse effects. On the other hand, excessive sodium intake is also undesirable here. Owners should avoid foods, treats and human food from the table with a high salt content. The sodium content should be kept below 0.4% in the dry matter of the feed at this stage. In dogs with a higher degree of heart disease, a moderate to more severe sodium restriction of 0.08-0.25 % of dry matter is already recommended. Potassium is one of the most monitored elements in cardiac patients. Some drugs can induce hypokalaemia, others hyperkalaemia. Both conditions are undesirable and may cause cardiac arrhythmias. Hypokalemia is less common in dogs and can be addressed by increased potassium supplementation from the diet. Hyperkalemia may be a greater problem because drugs are currently used that cause an increase in serum potassium. Magnesium deficiency can also cause arrhythmias, reduced cardiac contractility and skeletal muscle weakness. Food for dogs with heart disease should contain at least the minimum recommended amount of magnesium, i.e. 0,06 % on a dry matter basis. An increased magnesium supply in the food may help to suppress cardiac arrhythmias. Dogs with heart disease may also benefit from an increased intake of certain substances that may positively influence the course of the disease. These include taurine, L-carnitine, arginine, omega-3 fatty acids, B vitamins and antioxidants. Taurine is a derivative of the amino acid cysteine and is also classified as an amino acid. It is involved in bile acid conjugation and is essential for normal retinal and myocardial function. Animals can synthesize it in the liver, where it is formed by conversion from sulfur amino acids. Dogs are able to synthesize taurine in sufficient quantities, so it is not considered an essential nutrient for them. However, in some breeds, an association has been found between the development of dilated cardiomyopathy and reduced serum taurine concentrations. For dogs with heart disease, a dietary supply of taurine of at least 0.1% on a dry matter basis is recommended. Dogs with heart failure also have lower plasma concentrations of omega-3 fatty acids, so it is advisable to supplement their food. In addition, they are anti-inflammatory and reduce the incidence of cardiac arrhythmias.

MVDr. Eva Štercová, Ph.D.