Most feline heart problems are acquired (meaning that they develop later in life than congenital defects, which are present at birth), but regardless of their cause, symptoms may include:
- Lack of appetite
- Lethargy
- Rapid breathing
- Increased respiratory effort
- Collapse
- Sudden onset of paralysis (usually in the hind limbs)
Importantly, many cats that are diagnosed with heart disease initially show no signs of disease, which is why having your cat visit the veterinarian regularly is important.
Diagnostic Testing
When listening to your cat’s chest, your veterinarian may pick up a murmur, an arrhythmia, or changes in lung sounds that could fit with a cardiac condition. An echocardiogram may be recommended to evaluate cardiac structure and function. Thoracic radiographs (X-rays of the chest) may be recommended to evaluate heart and blood vessel size, the status of the lungs, and to rule out the presence of any fluid that may build up in the chest cavity of cats with heart disease. An electrocardiogram (ECG) may be recommended to look for abnormal electrical activity in the heart (arrhythmias).
Measurement of blood pressure and blood thyroid hormone levels will commonly be recommended to rule out hypertension (high blood pressure) and hyperthyroidism, both of which may cause thickening of the left ventricle. These tests are important to distinguish heart thickening that can occur secondary to these problems from primary hypertrophic cardiomyopathy (HCM), the most common heart disease in cats. More on that later.
A measurement of N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels in the blood may be recommended. This protein is released by the heart when it is abnormally stretched, as commonly occurs with heart disease, and blood NT-proBNP levels can be used as a screening test in cats suspected of having heart disease prior to an echocardiogram, which is the gold standard for the diagnosis of most feline heart diseases.
One study showed that 90% of the cats that had elevated NT-pro BNP levels had heart disease, and this test can be especially helpful in distinguishing respiratory difficulty caused by cardiac disease from that caused by non-cardiac diseases. While not currently recommended for all cats during a wellness exam, this test can be especially useful as an initial diagnostic test in cats that have heart murmurs and/or other abnormal heart sounds in the absence of symptoms. NT-proBNP levels can also be used to monitor the response of cats with heart disease to therapy.
Cardiomyopathy
Cardiomyopathies, which are primary diseases of the heart muscle, account for most cases of feline heart disease. HCM, characterized by thickening of the walls of (usually) the left ventricle, is by far the most common heart disease of cats. This thickening impairs filling of the ventricle and can predispose to congestive heart failure (CHF) and the development of thrombi (clots) in the heart that can be ejected into the body (called thromboembolism). Thromboembolism can result in the blockage of blood supply to various parts of the body, most commonly the hind limbs (called a saddle thrombus), where paralysis can ensue.
“HCM affects one out of seven cats, which is a consistent finding across multiple prevalence-type studies. Fortunately, many cats with HCM do not necessarily develop adverse outcomes, and echocardiography can help better assess their risks for outcomes such as CHF or thromboembolic disease,” says Weihow Hsue, DVM, assistant professor in the section of cardiology at Cornell University’s College of Veterinary Medicine.
Restrictive cardiomyopathy (RCM) is a condition in which the walls of the ventricle become infiltrated with fibrous material that restricts its ability to expand to accept blood that is entering it during relaxation (i.e., between contractions of the heart). Like HCM, RCM predisposes cats to congestive heart failure and thromboembolism, and the prognosis for cats with RCM is generally less favorable than that of cats diagnosed with HCM.
Dilated cardiomyopathy (DCM) is characterized by thinning of the muscle of the ventricles, making it more difficult for the heart to pump blood efficiently. Feline DCM, initially seen quite frequently as the result of dietary deficiency of the amino acid taurine, has become rare due to the fact that most commercially available cat foods are now appropriately supplemented with taurine.
Diagnosis of heart problems in cats tends to rely on multiple tests, and your veterinarian may recommend referral to a board-certified veterinary cardiologist if there is concern for heart disease in your cat.
Treatments
The treatment of feline heart problems usually relies upon the use of diuretics to address congestion in the lungs, oxygen therapy to increase the delivery of oxygen to the tissue of the body, antithrombotic drugs to decrease the likelihood of thromboembolism, drugs to improve the pump function of the heart, and, in rare cases, antiarrhythmic drugs to address arrythmias. The removal of fluid that can accumulate around the lungs within the chest cavity (called pleural effusion) via a procedure called thoracocentesis may also be required to improve respiration in cats with CHF.
Regular rechecks are important to fine tune the medical management of cats with heart disease, and these rechecks may include repeat echocardiograms, thoracic radiographs to evaluate the lungs, and blood work to assure that cardiac therapy is not negatively impacting other organs, including the kidneys and the liver.
At Home
Minimizing stress is important for cats showing signs of heart disease, and learning to administer medications in as stress-free a manner as possible is crucial. Your veterinary clinic can show you ways to do this. Churu paste, for example, can make medication time a positive experience, and you can ask about the possibility of having flavored liquid versions of medications compounded by the pharmacy.
Dr. Hsue says counting resting respiratory rates is the most helpful thing owners can do to catch the potential onset of congestive heart failure (CHF). The normal respiratory rate for healthy cats is 15 to 35 breaths per minute. Any rates higher than 35 breaths per minute should prompt a call to the veterinarian. Your veterinarian will provide guidance regarding how frequently respiratory rates should be monitored.
Signs of difficulty walking, paralysis, or collapse should prompt immediate referral to a veterinary emergency facility, as these may be indicators of thromboembolism that requires immediate medical intervention.
While feline cardiac diseases can’t be cured, the consequences can be controlled in many cases, giving you more time with your beloved cat.
Dr. Weihow Hsue is an assistant professor in the section of cardiology at Cornell University’s College of Veterinary Medicine.
