Hypertrophic Cardiomyopathy
Hypertrophic cardiomyopathy is the most common heart disease in cats. This disease is characterized by a progressive thickening of the heart muscle, resulting in a very small left ventricle with a very thick wall. Most cases of hypertrophic cardiomyopathy are idiopathic, meaning the cause is unknown, but it can sometimes occur secondary to hyperthyroidism, acromegaly, or high blood pressure.
In this disease, the thick walled left ventricle ceases to function properly and cannot fill very efficiently. As a result, blood is not being pumped throughout the body in the way it should, resulting in many of the clinical signs that are seen. Common signs include difficulty breathing, labored breathing, anorexia, and exercise intolerance.
Sometimes this disease will be so far advanced without treatment that the cat forms a blood clot in the arterial system. This blood clot then travels through the bloodstream until it reaches a point where it gets stuck. This usually occurs where the aorta splits to go to the two back legs. If a blood clot gets lodged in this area, the cat will be paralyzed in the rear legs, in pain, and may have blue toenails and a rock-hard calf muscle. If this occurs, it is a medical emergency and your cat should be rushed to a veterinary hospital right away. Unfortunately, the prognosis in this case is extremely guarded, and the cat may not survive.
Your veterinarian may detect a heart murmur during a physical exam in an apparently healthy cat that will tip him/her off to a possible diagnosis of cardiomyopathy. In this case (or in a cat that comes in with some of the above clinical signs), x-rays and an echocardiogram may be used to help provide a definitive diagnosis. Echocardiography is the best way to confirm a diagnosis of hypertrophic cardiomyopathy. Treatment for cardiomyopathy depends on the severity of the disease, but will most likely consist of diuretics to decrease the load on the heart, as well as other drugs to improve the function of the heart. This disease can be controlled for some time if it is caught early enough, and you and your cat will be able to enjoy extra time together.