Cardiology For Cats

Cardiology for Cats

Regular veterinary checkups are a key component in keeping your cat’s heart healthy.

All cats are at potential risk for heart disease. In some cases, the signs are obvious, in others, a serious heart disorder can remain hidden for years and may present itself in a sudden, perhaps fatal, deterioration of function.

The best thing cat owners can do is to make sure their cats have thorough medical checkups at least once a year until the age of 8 years and then twice a year moving forward.  During this examination the veterinarian will carefully listen to your cat’s heart. While examination with a stethoscope cannot detect all feline heart diseases, it’s probably the most cost-effective approach to diagnosis in otherwise healthy cats.

How A Cat's Heart Works

Just like humans, a cat's heart is hollow, made of muscle, located in the center of the chest and has four chambers. The two upper chambers are called the atrium, which collects circulating blood, and the lower chambers are called the ventricles, which pumps blood from the heart. Additionally, the heart has a right and left side; so each side contains one atrium and one ventricle.

Here are the basics of how a cat's heart works:

  • Veins carry exhausted blood from the body to the right atrium
  • Blood is stored in the right atrium momentarily until being pumped into the right ventricle
  • The right ventricle pumps the blood into the lungs, where it is infused with fresh oxygen
  • The blood then flows from the lungs back into the heart via the left ventricle
  • The largest muscle of the heart, which is located in the left ventricle, pumps the freshly oxygenated blood to all other organs and body parts
  • Once the blood is circulated and exhausted, veins carry it back toward the heart via the right atrium to begin the process again

What Causes Heart Disease In Cats?

Heart disease is a condition in which an abnormality of the heart is present. According to the American Veterinary Medical Association (AVMA), heart disease in cats affects 1 out of every 10 cats worldwide. Most feline heart disorders are acquired during the course of an animal’s life, but others are present at birth.

 Heart disease in cats can be either congenital or acquired:

Congenital Defects

Congenital heart disease in cats is means present at birth, and can be inherited from the parents. Congenital feline cardiac disease is relatively rare, occurring only in an estimated 1%-2% of kittens. The most common congenital disorders are heart valve malformations and holes in the septa (wall separating right and left ventricular chambers).  Both types of congenital heart disease cause blood to flow abnormally through the defect. The disturbance in the blood flow causes abnormal vibration or a heart murmur in cats.  Medication may help some kittens with mild congenital defects live a long and happy life, but the prognosis for a severe defect at this time is poor.  Surgical treatment at this time is generally not feasible.

Acquired Disorders

Acquired, or adult onset heart disease in cats often occurs in middle-aged to older animals due to wear and tear on the heart structures, but can also result from feline myocarditis, an inflammation of the heart muscle; myocardial infarction, tissue death in an area of the heart muscle resulting from a blood clot; and “unclassified” cardiomyopathies, a category comprising hybrids of the various conditions. While occasionally observed in kittens, a disease called cardiomyopathy is almost always an acquired condition and is by far the most common among all adult feline heart disorders.  Feline cardiomyopathies account for almost 2/3 of all heart conditions diagnosed in cats. Please refer to section, “What is a Cardiomyopathy”.

Symptoms Of Heart Problems In Cats

There are several symptoms of heart problems in cats that cat owners should be on the lookout for, including:

  • Lethargy/weakness/inactivity
  • Difficulty with or discontinuing exercise
  • Shortness of breath or difficulty breathing possibly accompanied by fluid buildup in the lungs and chest
  • Sudden paralysis of the hind quarters
  • Fast breathing at rest
  • Fainting/collapse
  • Chronic coughing
  • Regularly elevated heart rate
  • Possible presence of a heart murmur

The above symptoms can indicate one of many possible diseases and is not specific to feline heart disease. If you notice any of the above symptoms, we recommend scheduling an appointment with our veterinarians immediately.

What is a Heart Murmur? 

A heart murmur is an abnormal sound heard with a stethoscope (auculted) during the heart beat cycle.  Most people are familiar with the two sounds a heartbeat makes when the heart valves are closing, "lub-dub". A murmur is an additional "whoosh" or "swish" sound.  

Heart murmurs can be present at birth (congenital) or develop later in life. A heart murmur isn't a disease, but heart murmurs may indicate an underlying heart problem. Some cats will have heart disease without a heart murmur.  Also, heart murmurs can be harmless (innocent).  There is no treatment to cure a cat's heart murmur.  An echocardiogram (ultrasound of the heart) is the best way to determine how significant a cat's heart murmur is and how it will affect their life.  

If the veterinarians at Metropolitan Veterinary Center auscult a heart murmur during your cat's physical examination we will consult with you regarding the best way to proceed. 

What Is Cardiomyopathy?

Cardiomyopathy, literally means “disease of the heart muscle".  It is brought about by a structural abnormality in the muscle of one or both of the ventricular heart chambers. The affected chamber(s) takes on a thickened, dilated or scarred appearance. The left ventricle is always affected, but rarely, the right-chamber may also be involved.  In general, the heart muscle, either grows too thick, or it stretches, becoming too thin. In either case, the abnormality causes the heart’s blood-collecting and blood-pumping systems to malfunction.  A malfunctioning heart may lead to congestive heart failure resulting in respiratory distress, arrhythmias, blood clots, and, in some cases, sudden death.

Most feline cardiomyopathy origins are either genetic or unknown. Some, however, are secondary diseases, whose causes are specifically identifiable, such as hyperthyroidism or high blood pressure. 

Male and female cats of any age—even kittens—are susceptible to one form or another of cardiomyopathy, although most patients are middle-aged males. And among all feline breeds, Maine Coons and Ragdolls seem to be at elevated risk.

There are three main types of cat cardiomyopathies:

Hypertrophic Cardiomyopathy (HCM)

  • The most common type by far, diagnosed in 85-90% of primary cardiomyopathy cases.
  • The cause of HCM is unknown, but believed to have a hereditary influence. Certain breeds of cats appear to be predisposed.  Specific genetic mutations have been identified in both the Maine Coon and Ragdoll breeds of cat. The role of genetics has not been definitively determined in other families or breeds, although some association has been documented in American Shorthairs and Persians.
  • Middle-aged male cats may be more commonly affected. 
  • Sometimes heart muscle thickening similar to HCM can develop secondary to other disorders such as hyperthyroidism (elevated thyroid hormone), systemic hypertension (elevated blood pressure) and aortic stenosis
  • Characterized by a thickening of the muscle tissue associated with the left ventricle. This thickening results in poor heart function and, sometimes, obstruction of blood flow from the heart. It also causes the upper heart chambers to become enlarged. The consequence of these combined factors is a condition in which the heart fails to relax fully and thus unable to fill fully with circulating blood.
  • The end result can be increased fluid pressure in the lungs and shortness of breath. In addition, blood clots may develop in the left atrium that may breaks apart, propelling small pieces into the circulation. These clots common lodge in the artery of the hind legs  and eventually lodge in an artery leading to the legs causing a sudden onset of lameness or paralysis, and often severe pain.

Restrictive Cardiomyopathy (RCM)

  • The second most common type, accounting for approximately 10 percent of the primary heart muscle diseases diagnosed in cats. 
  • This condition is caused by the excessive buildup of scar tissue on the inner lining and muscle of the ventricle, which prevents the heart from relaxing completely, inability to fill adequately and empty completely with each heartbeat. Most often affecting geriatric cats, this disorder is also characterized by severely enlarged atria and reduced cardiac filling and pumping efficiency.

Dilated Cardiomyopathy (DCM)

  • Relatively rare anymore, probably accounting for only1-2% of primary cardiomyopathy cases.
  • Cats deficient in an amino acid called Taurine are predisposed. 
  • In this condition, the heart becomes enlarged, the heart muscle becomes dilated, thin and weakend. It is characterized by an enlarged and poorly contracting left ventricle. The ventricles poorly contract and don't pump blood well.  

Diagnosis Of Hypertrophic Cardiomyopathy In Cats

Diagnosing hypertrophic cardiomyopathy in cats begins with one of the most effective diagnostic tools for detecting heart disease in cats: A Cardiac Examination. A cardiac examination allows us to follow a thorough investigative protocol to determine the presence and extent of hypertrophic cardiomyopathy in cats. A cardiac examination can include some or all of the following procedures:

  • Physical exam: We listen to your cat's heart and lungs with a stethoscope to check for abnormal sounds
  • Blood pressure: We perform a standard, non-invasive blood pressure test to monitor systolic and diastolic pressure
  • Electrocardiogram (EKG): We measure the electrical activity of your cat's heart to diagnose heart murmur in cats, among other conditions
  • X-Rays: We can view the heart's overall size, its positioning in the chest, and the general condition of the lungs
  • Blood analysis: We can perform a complete blood work chemistry to help assess the general health of our patient. A blood chemistry analysis can also determine the level of thyroid hormone present in the bloodstream. This is very helpful when evaluating hypertrophic cardiomyopathy in cats, because an overactive thyroid gland can be an underlying cause of heart disease.
  • Ultrasound: This views and measures your cat's heart's chamber, valves and muscles, as well as the major cardiac vessels using soundwaves. In some cases, sedation may be required. 

Treatment Of HCM

Presently, there is no cure for hypertrophic cardiomyopathy in cats. Changes to the size and structure of the heart muscle are irreversible. The longer HCM is allowed to go untreated, the more severe any changes become. However, in some cases where the heart disease is secondary to a treatable condition such as hyperthyroidism, then the symptoms may be alleviated when the underlying condition is corrected.

The good news is that your veterinarian can prescribe several different types of medication that help reduce the risk of congestive heart failure in cats resulting from HCM. In some cases, medication can help:

  • Relax the heart muscle
  • Slow down heart rate
  • Decrease the workload of the heart

These changes provide the heart more time to fill and drain, thus allowing for a reduced chance of damage and failure. Because heart medication is modifying the function of the heart, it is important to strictly follow your veterinarian's recommendations for dosage and administration frequency.

Owners of cats with HCM should monitor their feline friends for any changes in their condition, even if they seem minor at first glance. This includes learning how to monitor respiratory rates and other vital signs at home, which a veterinarian can help with. It is also important to come in for a exam with any changes in your cat's health or behavior and keep up all recheck appointments for the best outcome.

Complications Associated With HCM

Many felines diagnosed with HCM eventually develop signs of congestive heart failure. Cats with HCM are at risk for developing blood clots that can escape the heart and eventually become lodged in a blood vessel that has become too narrow. This is called a thromboembolism. A common area for this to occur is the hind quarters region, at the point the aorta splits before going into each rear leg. If this happens, paralysis and severe pain will result. In fact, the paralysis and pain are very common reasons many owners initially bring their cat to see a veterinarian. However, what they thought might be a broken leg or lameness is actually hypertrophic cardiomyopathy in cats.

Due to the nature of how blood clots fragment and disperse throughout the body, cats that experience blood clotting once are at a significantly increased risk of developing another clot within the following weeks or months. Because of the somber prognosis for cats that have suffered a thromboembolic event, some owners elect euthanasia.

Prognosis For Cats With HCM 

Even though hypertrophic cardiomyopathy in cats is incurable, the old saying, an ounce of prevention equals a pound of cure, still greatly applies to cats living with heart disease or congestive heart failure for cats in one form or another. 

  • HCM can worsen quickly or progress slowly over a period of years
  • HCM can remain undetected in some cats until the advanced stages, and the time between diagnosis and death can be a matter of weeks or months
  • HCM can remain mild in some cats and never progress to the advanced stages, while other cats will progress to the advanced stages despite medical intervention

The existence of these variables and possibilities make both preventive and follow up care of the utmost importance where heart disease and congestive heart failure are concerned.

Stages of Heart Disease

There are also various stages of heart disease and congestive heart failure in cats that veterinarians use to determine severity:

  • Asymptomatic: Heart disease in cats is detected, but there is a lack of any outward signs. Additionally, a heart murmur in cats or arrhythmia may also be present.
  • Mild to moderate heart failure: Significant clinical signs of congestive heart failure are in evidence both at rest and while active.
  • Advanced heart failure: Critical clinical signs are evident, including respiratory distress, ascites (fluid in the body cavity), and profound exercise intolerance.The prognosis will worsen with each passing stage, and the need for aggressive treatment will increase.

Scheduling Cardiology Tests For Your Cat

If you suspect that your feline friend might be at risk for, or suffering from, any heart conditions, please contact us immediately to schedule an appointment today.