Heart failure is the inability of the heart to meet the oxygen demands of the body tissues, because a failing heart cannot pump the blood to all parts of the body normally. Whatever the cause of heart disease, heart failure is the final outcome when the disease becomes advanced. The kidneys sense this heart failure and set up a protective mechanism by retaining salt and water which increases the circulating blood volume and thereby brings the cardiac output back to normal. Eventually, the failing heart can no longer handle this increased blood volume, and blood backs up. Fluid from the blood leaks into the body tissues and the lungs. This is edema, or swelling.
It has been established that the leading underlying cause of sudden and unexpected death of dogs is heart disease. In fact, in many cases sudden death is regarded as heart-related if no other cause of death is obvious. Heart diseases may be genetic, hereditary or they can develop as a result of an infection, parasitic infestation, or tumor.
Types of Heart Failure
There are three types of heart failure:
- In right-sided heart failure the right side of the heart fails; the blood returning to the heart from throughout the body backs up, and fluid accumulation is most noticeable in the liver, abdomen, and limbs.
- In left-sided heart failure blood returning from the lungs to the heart backs up, and fluid accumulates in the lungs.
- In right- and left-sided heart failure both sides of the heart fail and the entire blood circulation system is affected.
Although many dogs, particularly as they age, have heart disease, symptoms only become evident when the heart starts to fail. The signs depend on the severity of the disease and on which side of the heart is affected, and include some or all of the following:
- General weakness and fatigue, is particularly noticeable after exercise. Some dogs may faint if forced to exercise.
- Shortness of breath and a cough is most evident in left-sided heart failure.
- Swelling of the abdomen and limbs is most evident in right-sided heart failure. This edema is due to an accumulation of fluid throughout the body. Pressure on the swollen feet will leave a deep indentation or depression that is slow to disappear. This condition is called pitting edema.
- Bluish appearance to the tongue and gums develops as a result of the poor blood circulation.
- Poor appetite, vomiting, diarrhea, or constipation may occur from insufficient blood circulation to the liver and digestive organs.
- Excessive drinking and urination
- Increased heart rate and weak pulse
Diagnosis and Treatment
A veterinarian can diagnose heart disease in a dog from the history, symptoms, and a physical examination. However, some or all of the following diagnostic procedures will be necessary to try to determine the cause and degree of heart failure. These procedures will assist the veterinarian in choosing the best method of treatment: stetoscope examination; X-ray examination; blood and urine tests; electrocardiogram; cardiac catheterization; angiocardiography; and phonocardiography. Although some expense is involved in having these tests done on a dog with heart disease, it is money well spent because an accurate diagnosis is the key to effective treatment.
Treatment of heart failure in dogs is very similar to treatment of this condition in humans. It is not complicated or expensive after the initial diagnosis and treatment regimen have been established. Initial treatment may require the dog to be hospitalized to allow the veterinarian to monitor its response to treatment, and to determine the drugs needed for treatment and their most effective dosage level. The approaches of treatment are:
- Activity restriction. Many dogs with heart failure will need to have their exercise restricted, and this can vary from minimal to severe restriction. Because dogs are not as cooperative as people, tranquilizers, sedatives, or enforced crate rest may be required.
- Low-sodium diet. Salt restriction is essential in treating heart failure, because sodium chloride is retained by the body and this leads to edema. Specially formulated low-sodium diets, such as Prescription Diet h/d made by Hill's, are available from your veterinarian. However, dogs (like people) often find salt-free diet food unpalatable at first, so it may take some determination on the owner's part to make this essential changeover. Water must never be restricted in dogs with heart failure, but softened water should be avoided, because it has a high salt content.
- Diuretics. These are drugs used to stimulate kidney activity to remove retained water from the body via urination, which will be increased in amount and frequency.
- Other drugs. There are many drugs available today which are used to smooth or slow irregular or fast heartbeats.
- Oxygen, bronchodilators, and cough suppressants. Some or all of these may be needed in specific cases of heart failure to help the lungs function efficiently.
- Surgery. Treatment of heart disease through surgery is not common in dogs, not because it cannot be done, but because of the expense. Some veterinary practitioners and all university small-animal veterinary departments perform surgeries in dogs for congenital defects of the heart, heart valve defects , heart injury from accidents, heartworm removal, insertion of electronic pacemakers, and even transplants.
The prognosis will depend on how early the dog is brought to the veterinarian for treatment and on the severity of the disease. The majority of dogs respond very well to treatment, and lead active, happy, and even long lives, quite often dying from old age or causes unrelated to heart failure. However, except in rare cases, heart failure is an incurable and progressive disease and will require treatment for the rest of the dog's life. Most dogs are older and have been with their owners a long time, and the emotional bonds between them are very strong. For these reasons the majority of such owners feel the treatment of heart failure is well worth while and are most grateful when they see their dog become happy and active again.
About 90% Cavalier King Charles spaniels develop MMVD heart disease by the age of 10 years