Heart Disease in Cats
Much like humans, cats also can suffer from heart disease. No doubt there will be some that wonder how an animal can suffer from the same disease that afflicts so many humans, when so many of us know that we should be following a recommended diet and getting the proper exercise. Much like humans, the diets of our pets have changed considerably over the years.
There are many pet owners who believe the key to their pet's happiness is through food. As a result, like humans, many of our pets are now overweight. We also see a lot of pets that don't get as much exercise as they should. So, in many cases it should come as no surprise that many cats suffer from heart disease. We should also consider, that as many cats get older, they tend to slow down and spend much of their time sleeping.
In the simplest of terms, cardiomyopathy simply means “heart muscle disease” and can refer to any disease that affects the heart muscle itself. Cardiomyopathy affecting cats are typically categorized as hypertrophic, dilated or congested, or restrictive. Those cardiomyopathy's that don't fit into those categories may be classified as intermediate or inter-grade. Disease of systolic dysfunction is known as dilated cardiomyopathy, which means the muscle can't adequately contract and has trouble pumping blood out of the heart. In this condition the heart becomes enlarged and globular like a balloon, and the muscle walls become very thin.
Between 1987 and 1994, it was discovered that dilated cardiomyopathy in cats was often associated with a dietary deficiency of taurine. Taurine is an essential amino acid. Once manufacturers of cat foods began adding more taurine, at least 90% of the disease disappeared in the United States. It has been found that if a cat's dilated cardiomyopathy is caused by a deficiency of taurine, adding it back into their diets will resolve the cardiomyopathy.
In those cats where dilated cardiomyopathy is not a result of taurine deficiency and the cause isn't known, the disease is called idiopathic. Dilated cardiomyopathy today now accounts for at least 50% of all heart failure cases diagnosed in cats. In those cases where dilated cardiomyopathy is not a result of a taurine deficiency, the cause of the cardiomyopathy is unknown.
Another type of cardiomyopathy is known as hypertrophic, and that is a case of diastolic function, which refers to the heart filling with blood rather than contracting. As a result, the heart walls thicken, reducing the size of the heart chambers until they cannot adequately fill with blood.
A more recently discovered cardiomyopathy is known as restrictive. There are few documented cases of this type of cardiomyopathy by veterinarians. Restrictive cardiomyopathy is a result where the heart muscle lining of the heart chambers become so stiff that the heart cannot fill properly with blood. Effected cats may display a condition where portions of the heart wall don't function properly, but other portions appear normal or may just be thicker than normal.
For most felines who suffer from heart disease, cardiomyopathy is generally the diagnosis. It appears to affect every breed of cat known, but since such cases are not tracked, it's hard to know the percentage of cats affected by the disease.
There has been some research done which seems to indicate that hypertrophic cardiomyopathy contains a genetic component which affects certain breeds of cats, namely the Maine Coon breed. If the cat has been
diagnosed with cardiomyopathy, it is quite possible their kittens will inherit the disease. Any cats diagnosed with cardiomyopathy for this reason should not be bred.
Cats of any age may be affected, but hypertrophic cardiomyopathy is most often found in young and middle-aged cats. With dilated cardiomyopathy, any breed of cat can be affected, but Siamese, Abyssinian, and Burmese breeds appear to be predisposed to the disease.
Symptoms can vary from cats that appear totally unaffected, to those who die suddenly. It is possible that those cats that are mildly affected can live a totally normal life with the disease and may only be diagnosed when a stressful event makes the heart work too hard, such as during a teeth cleaning or a visit to the groomers to get their nails done. Any stressful event can cause an increase in the heart rate, providing less time for the heart to fill. As the heart is already having issues making it difficult to fill, shortening the time that is allowed fill, may push the heart to failure. (See YouTube video at the bottom of this post for more on symptoms).
Some signs you may see in cats affected by cardiomyopathy include laboured breathing from fluid filled lungs, which is known as pulmonary edema. Laboured breathing may also result from pleural effusion or excess fluid in the chest cavity. Cats may also exhibit lethargy, weakness, mental depression, loss of appetite, hind limb pain or paralysis. The hind limb pain or paralysis may result from blood clots secondary to the cardiomyopathy. Embolization occurs when the clot breaks off and gets stuck in another location, blocking the normal flow of blood. Such clots usually occur in the hind legs where the aorta splits. Such a clot will usually result in pain or paralysis of one or both hind limbs.
The diagnosis of cardiomyopathy is most often based on the symptoms and through diagnostic testing. An electrocardiogram may be used to detect abnormal heart rhythms. An x-ray can show if there is excess fluid buildup in the chest and lungs and provide a silhouette image of the heart itself. A cardiogram can also show how thick the walls of the heart are itself, as well as how good the blood is being pumped. Generally, clinical signs will dictate how bad the disease itself is. In cases where the disease itself is bad, treatment is unlikely to prolong the cat's life, but it can improve what life it has left. Cats who show no symptoms may not require any type of therapy, but once heart failure is apparent, the recommended course of treatment is drug therapy.
For fluid in the lungs and congestion, symptoms are generally controlled with a diuretic such as Lasix (furosemide). A diuretic will force the kidneys to get rid of excess salt and water. Vasodilator drugs can also help open constricted blood vessels and help control congestion, making it easier for the cat to breathe. Calcium channel blockers and beta blockers may also be used to help slow the heart rate in hypertrophic cardiomyopathy, giving the heart more time to fill. Digoxin may be given to help strengthen the heart and regulate blood pressure.
Veterinarians practising holistic remedies may prescribe Hawthorne berries, which is said to make the heart muscle stronger. Another homeopathic remedy is Apis, which is a mild diuretic that can help get rid of excess fluids of pleural effusion. Cats with heart problems may also benefit from the coenzyme Q10.
Approximately 40% of cats with blood clots in the rear limbs regain use of those limbs within a week of treatment. Providing surgery for such issues on cats is generally avoided as they are high anaesthetic risks. Clot reducing drugs can help reduce the stickiness of blood platelets which decreases the chance of clots forming. For those cats that undergo corrective surgery or are provided anticlotting drugs, up to 50% will suffer another clot.
Cats with dilated cardiomyopathy which are a result of a taurine deficiency usually have the best prognosis. If they survive the initial two weeks after taurine added to their diet, their outlook is quite good. Those cats with idiopathic dilated cardiomyopathy generally have a poor outcome, and a much lower survival rate. The same can be said of those cats diagnosed with restrictive cardiomyopathy. About 50% of cats showing signs of hypertrophic cardiomyopathy will die within three months. Most cats as shown no clinical signs can be expected to survive more than five years.
As always, if you have anything to add or want to suggest another topic you would like information on, please leave them in the comments section below.