What Are the Causes of an Enlarged Heart in Cats?

Feline heart disease involves a decreased ability to distribute oxygen and blood to the other organs of a cat's body. When the four chambers of the heart---the two upper atria and the two lower ventricles---become diseased and enlarged, your cat's entire body will be affected. Your pet may not be able to breathe, may experience exercise intolerance and general weakness, and can begin coughing. Symptoms of heart disease may not show until the disease is far advanced and the enlarged heart becomes severely dysfunctional, say veterinarians at Portland Veterinary Specialists. Veterinary therapy begins when your veterinarian diagnoses the type of heart disease presenting in your pet and works to increase the heart's function.

  1. Hypertrophic Cardiomyopathy

    • A disease mainly of middle-aged male cats, hypertrophic cardiomyopathy (HCM) occurs when the muscles of the heart's ventricles grow unchecked, limiting the heart's capacity to pump blood. Lessening of cardiac output leads to heart failure with symptoms including ascites (the accumulation of fluids in the cat's abdominal cavity), fluid in the lungs and the development of a heart murmur, reports Dr. Scott McKay of PetEducation.com. Some cats become suddenly paralyzed in the rear legs because of blood clots lodging near the spine; some cats have no symptoms until sudden death occurs. Because the cause of HCM is generally not known, veterinarians treat the disease as they do congestive heart failure, with medications to relieve the symptoms and improve heart function.

    Dilated Cardiomyopathy

    • Dilated cardiomyopathy (DCM) happens when the chambers of your cat's heart---meaning the areas inside the muscular walls of the heart---become dilated and enlarged. This dilation prevents the heart muscle from contracting to its full extent and the heart valves from completely closing. DCM can lead to congestive heart failure, abnormal heart rhythms, blood clots, shock and renal failure, advise the veterinarians of PetPlace.com. Causes of the disease may include hyperthyroidism, chronic low blood potassium, taurine deficiency, toxic injury and myocarditis---inflammation or infection of the middle layer of the heart muscle. Your cat may develop the disease through no known cause. Therapy typically includes diuretics to relieve fluid buildup and medications to lower blood pressure. Other medications may be necessary to regulate heart rhythms, lessen pain and prevent blood clot expansion.

    Restrictive/Unclassified Cardiomyopathy

    • In cats with restrictive cardiomyopathy, the left atrium of the heart shows severe enlargement, but the muscular structure of the ventricles remains normal. Reduced circulation to both right and left ventricles results in lessened blood volume that may lead to blood clots in the atria. Veterinary diagnosis with a sonogram may show abnormalities in heart valve function. Your cat may present with similar symptoms to those of hypertrophic cardiomyopathy; the veterinary treatment is the same, reports the Merck Veterinary Manual. Veterinarians use the term "unclassified cardiomyopathy" to refer to heart muscle abnormalities that don't fit the descriptions of the other diseases.