Jazzie the cat
Photo courtesy Dr. Teri Ann Oursler
Cardiomyopathy means heart (cardio) muscle (myo) disease (pathy). Cardiomyopathies in cats fall broadly into five categories:
Dilated Cardiomyopathy
Dilated cardiomyopathy (DCM) was once the most common heart disease in cats. In the late 1980s, it was discovered that insufficient taurine in feline diets caused most cases of DCM. Taurine is an amino acid that cats cannot produce but must obtain by eating meat.
In dilated cardiomyopathy, the heart muscle weakens, the heart becomes large, and the blood circulates less effectively. Eventually, fluid builds up in the lungs (pulmonary edema) or in the chest cavity (pleural effusion), a situation that is referred to as congestive heart failure (CHF).
The food you feed your cat must contain adequate amounts of taurine. This is one reason why home cooking for cats is risky. Once the cause of DCM was identified, all commercial diets were supplemented with additional taurine to prevent this disease from developing.
Restrictive Cardiomyopathy
With restrictive cardiomyopathy, the muscles of the lower ventricles (chambers of the heart) stiffen, making it more difficult to fill the ventricles with blood when the heart relaxes between beats. This causes the atria (upper chambers of the heart) to enlarge, eventually resulting in congestive heart failure. The cause of restrictive cardiomyopathy is unknown.
Cardiomyopathy of a Non-specific Appearance (Unclassified)
Some cases show signs appearing to be primary heart muscle disease but do not fit into any well-defined category. Some veterinarians refer to these cases as unclassified cardiomyopathies. The cause is unknown, and little is known about the outcomes of cats with this form of heart disease. This category has not been studied extensively and might represent several different diseases.
Arrhythmogenic Right Ventricular Cardiomyopathy
This is a poorly understood cardiomyopathy of cats that mostly affects the right ventricle (right lower chamber), causing it to lose muscle, which is replaced by fat. The right ventricle dilates (enlarges). Arrhythmias are relatively uncommon in the feline form of this disease, compared with the dog or human version of this type of cardiomyopathy. Congestive heart failure often occurs, resulting in ascites (fluid build-up in the belly).
Signs
Before developing congestive heart failure, cats show few, if any, clinical signs or symptoms of disease with any of the cardiomyopathies. Your veterinarian might detect a murmur or other abnormal heart sound with their stethoscope at a routine examination, but cats can have murmurs for reasons other than cardiomyopathy.
Signs of congestive heart failure can include shortness of breath or fast, open-mouth breathing, an abnormally fast heart rate, and fainting.
Diagnosis
Diagnosis of cardiomyopathies often begins with chest X-rays, in which a veterinarian finds a big heart, often with an abnormal shape. However, this finding doesn’t tell the veterinarian what specific type of cardiomyopathy is present. And some cardiomyopathies are mild enough that the chest X-rays show a normal heart outline. To fully diagnose a cardiomyopathy, and often to determine its severity, requires an echocardiogram (an ultrasound examination of the heart). In many cases, this will require a referral to a cardiologist or other imaging specialist familiar with echocardiography of cats. The veterinarian will use the information received to determine the type and severity of the cardiomyopathy your cat may have and will find out if there are currently blood clots in the heart, and if there is a high risk of clots developing in the future.
Cats with cardiomyopathies often form blood clots in the heart, which can travel out of the heart, through blood vessels, causing blockage of blood to the hindlimbs (saddle thrombus), a front limb, or other organs.
If your veterinarian suspects dilated cardiomyopathy as the culprit, they might request a blood taurine test. Dilated cardiomyopathy in cats is almost always rapidly fatal (within months) if not treated with and is responsive to taurine. If the condition is due to taurine deficiency and taurine is given, there is a high probability of recovery and living a normal life. No harm can come from giving taurine, so there is nothing to lose by trying.
Therefore, if your veterinarian suspects your cat is experiencing a taurine-deficient cardiomyopathy, they might simply supplement taurine because it is a safe and inexpensive treatment and the only potential cure. If it turns out that the dilated cardiomyopathy is not due to taurine deficiency, no harm will have been done with the supplementation.
Treatment
Cats That Appear Normal But Have Cardiomyopathy (Subclinical Disease)
If diagnosed with dilated cardiomyopathy, taurine supplementation should be tried, ideally after collecting a blood sample for taurine analysis.
No drugs have been proven to change the course of subclinical disease with other cardiomyopathies. Some veterinarians prescribe a beta blocker like atenolol to reduce a condition known as systolic anterior motion of the mitral valve, or an ACE inhibitor to delay disease progression. Although theoretical reasons exist to prescribe these drugs, neither has been shown to alter disease progression.
A new drug (tacrolimus, rapamycin) is being studied to see if it can reduce the wall thickening in hypertrophic cardiomyopathy to prolong survival. A preliminary study suggested a benefit in wall thickness changes, but did not look to see if this resulted in better survival in those cats. It is not yet commonly available to most veterinarians.
Other common treatments, usually reserved for cats with evidence of marked left atrial (upper chamber) enlargement, are drugs that inhibit blood clotting, such as clopidogrel (Plavix) or rivaroxaban (Xarelto). These are given to reduce the risk of clot formation within the atria and the consequent risk of saddle thrombi.
Cats That Have Cardiomyopathy and Appear Ill (Clinical Disease)
Regardless of the type of cardiomyopathy, most treatment is directed at managing congestive heart failure. During the initial treatment period, congestive heart failure must be aggressively managed, and the risk of clots to the limbs and other organs (as well as sudden death) is always a concern. Most cats with congestive heart failure will be treated with a “water pill” (diuretic) such as furosemide (Lasix) and a clot inhibitor, such as clopidogrel.
Most cases of DCM today are not related to taurine deficiency. In such cases, treatment aims to manage congestive heart failure when it develops. Your veterinarian can choose the most appropriate drugs and therapies for managing your cat’s heart conditions.
Supportive Care and Monitoring
Your cat will require regular check-ups as determined by your veterinarian or veterinary cardiologist. How often depends on the type of cardiomyopathy your cat has and the treatment plan developed by your veterinarian. The recheck appointments may include a physical exam and recommended blood work, a blood pressure reading, and X-rays or other imaging, such as an echocardiogram, to check your cat’s current heart size and function.
It is important to watch your cat’s drinking, eating, and litter box habits for any notable changes. You may also be asked to monitor your cat’s sleeping respiratory rate, activity levels, and gait, and report to your veterinarian.
Prognosis (Outcome)
The prognosis depends on the type of cardiomyopathy your cat has.
If taurine deficiency is the cause of cardiomyopathy, most cats who survive for more than seven days after beginning taurine supplementation will recover, and most will ultimately need no ongoing therapy when the heart muscle returns to normal. This usually takes four to six months.
If your cat suffers from dilated cardiomyopathy, the prognosis is generally grave, with only weeks to months estimated. With hypertrophic, restrictive, and unclassified cardiomyopathies, those with subclinical disease may never develop signs of illness and live a normal life. Survival times and quality of life for those cats with congestive heart failure or other signs of heart disease differ depending on the extent of the disease when presented to your veterinarian and your cat’s response to medications.
Sudden death is always possible, especially in cats with hypertrophic cardiomyopathy.
Talk with your veterinarian about what to expect with your cat’s specific condition and how you can help them be as comfortable and healthy as possible.