The Classic Comprehensive Handbook of Cat Care
HEART AND BLOOD (CARDIOVASCULAR SYSTEM)
HEART DISEASE AND HEART FAILURE
Heart disease may occur in cats of any age. Just as in people, there are many causes of heart disease in cats. They include structural defects (e.g., leaky valves, abnormal holes between heart chambers), primary diseases of the heart muscle, bacterial infections of the heart and/or heart valves, heartworms, cancer, and diseases of the heart muscle secondary to other problems such as nutritional deficiency, thyroid disease, or high blood pressure. Disease of the blood vessels that supply the heart itself, arteriosclerosis, is an uncommon problem in cats.
Therefore, heart attacks that result in sudden death are rare in cats. Instead, disease in cats generally progresses gradually through several stages where it can be treated and its signs ameliorated before heart failure that requires emergency treatment or that results in death occurs. Many cats, however, go undiagnosed in the early stages of heart failure because the signs of heart disease may be very subtle and a cat may compensate for a failing heart by making changes in his or her activity level that go unnoticed by the average person.
A murmur, an abnormal sound in the heartbeat associated with turbulent blood flow through the heart, may be the first sign of heart disease. Kittens who have been born with heart disease are often diagnosed when a murmur is heard during their first physical examination given at the time of their kitten vaccinations. In older cats, a murmur may be a new finding that your veterinarian mentions at the yearly office visit for a physical exam and booster injection. Or you may hear a murmur as a shh sound interposed between the normal lub-dup sounds of the heartbeat when you are examining your cat at home.
If the murmur is intense enough, you even may be able to feel it through the chest wall by placing your fingers in the area where the heartbeat is normally felt. The presence of a heart murmur in any age cat is not necessarily something to be alarmed about especially if there are no other associated symptoms. However, it is something that requires a full veterinary evaluation since there are many causes of heart murmurs. Some murmurs result from serious diseases of the heart itself, including congenital defects and heart muscle diseases.
Others are associated with systemic diseases that cause anemia, fever, or high blood pressure. Still others are completely innocent and have no disease association at all. Your veterinarian will need to perform blood tests, a chest radiograph, an echocardiogram (ultrasound examination of the heart), and/or an electrocardiogram (electrical evaluation of the heart function) to differentiate among the various causes of heart murmur and to rule in or out heart disease in any age cat.
SIGNS OF HEART FAILURE
In cases of heart disease where you or your veterinarian do not detect a heart murmur or a murmur is not present, you may not notice any changes until the heart begins to fail. Sometimes the only external change is a reduction in a cat’s normal activity level, which may be misinterpreted as a normal decrease caused by maturity, boredom, or simple laziness.
Cats with this sign will often become abnormally short of breath if chased or enticed into play. When the heart failure becomes full blown it will usually be associated with rapid respirations and difficulty breathing (due to fluid accumulation in the lungs themselves and/or the chest cavity). The cat’s body temperature may become subnormal, the mucous membranes may become pale and develop a bluish color; your cat may be reluctant to move, eat, or drink and may even vomit.
The heartbeat of a cat with heart failure will often be extremely rapid and the pulses will be weak. (Heart rates persistently above 240 beats per minute are consistently associated with heart failure.) Some cats with heart failure have no femoral pulses at all, due to a blood clot that has lodged in the aorta. These cats may act as if their hindlegs are paralyzed. Death soon follows heart failure if treatment is not instituted when signs become evident.
INITIAL TREATMENT OF HEART FAILURE
The initial treatment of severe heart failure is directed toward lifesaving measures. Since many cats with obvious signs of heart failure are effectively in a state of shock, the most important thing you can do is seek a veterinarian’s aid. Veterinarians will administer oxygen if needed and diuretic drugs that reduce fluids interfering with effective respiration.
Veterinarians may even physically drain the chest cavity with a needle to remove fluid that is dangerously compressing the lungs. Various blood- pressure and heart-contraction-modifying drugs are also employed depending on the type of disease that is causing the heart to fail. During diagnosis and initial treatment absolute confinement in a hospital cage is essential to prevent even normal activity that may place too many demands on the cat’s weakened heart. This confinement is quite similar to the bedrest prescribed for people who have serious heart disease.
DIAGNOSIS OF HEART DISEASE
Once a cat in heart failure is stabilized or if a cat with heart disease does not require emergency care, your veterinarian will need to diagnose the underlying cause of the heart problem in order to provide the most appropriate treatment. This will involve a full biochemical evaluation of your cat, including evaluation of the blood and urine, chest radiographs, and echocardiogram, and/or special X-ray studies of the heart, and/or an electrocardiogram.
DIETARY DEFICIENCY CAN CAUSE HEART FAILURE IN CATS
One important form of heart disease in cats, dilated cardiomyopathy, in which the heart muscle loses its normal contractile ability, is often caused by a diet deficient in the amino acid taurine. Taurine deficiency may be further aggravated by potassium deficiency. The condition can be reversed when taurine supplements and a nutritionally complete diet are instituted before the heart is permanently damaged. Cases of dilated cardiomyopathy caused by nutritional deficiency can be entirely cured.
Prevent heart failure by investigating the cause of a heart murmur as soon as one is diagnosed in your cat; by feeding a nutritionally complete diet; by taking measures to diagnose and treat problems known to aggravate heart disease such as kidney failure, thyroid disease, and obesity before decreased heart function is severe.
CHRONIC TREATMENT OF HEART DISEASE
The prognosis for each cat with heart problems depends on the kind of heart disease present. The prognosis will have to be discussed with your cat’s veterinarian once his or her evaluation is complete. In general, heart failure secondary to other problems can often be completely controlled if diagnosed and treated soon enough.
Other forms of heart disease in cats cannot be entirely cured; therefore, treatment in these instances is generally directed at improving circulatory function. Medical treatment consists of various drugs and a controlled diet. Diuretic drugs help control sodium and water retention that accompany and aggravate heart failure. Blood vessel dilating drugs are used to lower high blood pressure and lessen the work that the heart must do to circulate the blood.
Aspirin in controlled doses can be safely used in cats to help prevent excessive blood clot formation that may occur when blood circulation is poor. And some cases benefit from digitalislike drugs that increase the strength of the heart muscle contraction. In addition to administration of drugs as needed, home care for cats with heart failure includes a sodium- restricted diet and confinement indoors. Cats who receive good home care may live longer, more comfortable, and more active lives than would seem likely when a diagnosis of heart disease is made.