How a Cat's Heart Works
A cat's heart has four chambers. The two upper chambers are called the atrium (plural atria) and the lower chambers are called the ventricles. Additionally, the heart has a right and left side, each containing one atrium and one ventricle. A cat's heart works as follows:
- 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 pulmonary vein
- 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 is Cardiomyopathy?
Cardiomyopathy is an acquired or hereditary disease of the heart muscle. This condition makes it hard for the heart to deliver blood to the body. Although there are many types of potential heart problems in cats, Hypertrophic Cardiomyopathy (HCM) is by far the most common heart condition to affect the feline population.
The prevalence of heart disease in the general cat population has been estimated to be as high as 14-34%. Heart disease can still be present even if your veterinarian doesn't hear any abnormal heart sounds on physical examination. At Cat Care Center, we understand the potential of underlying heart disease in the cat population. There are certain breeds of cats associated with higher risks for various forms of heart disease. We will guide you in making decisions to pursue genetic testing if available for your breed and screening tests for Feline Cardiomyopathy. We believe knowing as much as we can about each and every one of our patients allows us to guide you to make informed decisions throughout your cat's life.
What Causes Heart Disease in Cats?
Heart disease in cats can be either congenital or acquired:
1. Congenital heart disease - your cat was born with this heart condition; it can be inherited from their parents. These are typically young cats. This can be from malformations of heart valves and defects in the wall that divides the right and left halves of the heart.
2. Acquired heart disease - these are the cardiomyopathies most of us are familiar with. Age range is typically 3 months to 19 years.
Acquired heart disease is further broken down into two categories:
a. Primary Cardiomyopathies
- Hypertrophic Cardiomyopathy
- Dilated Cardiomyopathy
- Restrictive Cardiomyopathy
- And others
b. Secondary causes of acquired heart disease
- Chronic severe anemia
- Heartworm disease
- And others
There are also various stages of heart disease that veterinarians use to classify cats. These universal classifications are based on diagnosing the particular type of heart disease, treatment options if available for that particular classification, and follow-up care.
- At risk cats
- 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 changes: This stage there are mild to moderate changes seen in cardiac ultrasound and other tests, but the cat is still asymptomatic.
- Cardiac heart failure: This means the cat is actively exhibiting signs of heart failure, was recently treated, and is stabilized from active congestive heart failure.
- Advanced heart failure: Critical clinical signs are evident, including respiratory distress, ascites (fluid in the body cavity), and profound exercise intolerance. This stage is no longer responding to heart failure treatments.
Symptoms of Heart Problems in Cats
There are several possible symptoms of heart problems in cats that cat owners can be on the lookout for, including:
- Lethargy, weakness, and inactivity
- Difficulty with or discontinuing exercise
- Shortness of breath or difficulty breathing
- Sudden paralysis of the hind quarters, or less commonly, a front leg
- Shallow, fast breathing during dormancy (not panting)
- Fainting and collapse
- Regularly elevated heart rate
- Behavioral change
- Possibly coughing
The above symptoms can indicate one of many possible conditions, including feline heart disease and potentially something unrelated to the cardiovascular system. If you notice any of the above symptoms, we recommend scheduling an appointment with our veterinarian immediately.
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
- Ultrasound: We can view and measure your cat's heart's chambers, valves, and muscles, as well as the major cardiac vessels using sound waves and without any pain or invasion
- Blood pressure: We perform a standard, non-invasive blood pressure test to monitor systolic and diastolic pressure
- Electrocardiogram (ECG): 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, including a proBNP test. This test gives us a numerical measure of heart muscle enlargement. As the heart muscle fibers stretch, this peptide is released into circulation. This test is used as a screening tool in cats we feel are at risk.
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.
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. At this time, there is not a specific research-proven treatment for cardiomyopathy. However, there are veterinary cardiologist-recommended medications that do apply to certain stages of this disease. It is necessary to do a full medical and cardiac diagnostic evaluation to rule out treatable diseases that can lead to heart disease, to determine what stage your cat may be in, and any recommended therapies for that stage. However, in some cases where the heart disease is secondary to a treatable condition such as hyperthyroidism, the symptoms may be alleviated when the underlying condition is corrected.
Depending on the type and stage of heart disease, Dr. Lacie can prescribe medication that may help reduce some of the risks associated with feline heart disease. In some cases, medication can help:
- Relax the heart muscle
- Slow down heart rate
- Decrease the workload of the heart
- Prevent blood clot formation
These changes provide the heart more time to fill and drain, thus allowing for more cardiac efficiency. 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 cardiomyopathy 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 an exam with any changes in your cat's health or behavior, and attend all recheck appointments for the best outcome.
Complications Associated With HCM
Many felines diagnosed with cardiomyopathy 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. This is a medical emergency and needs to be seen by a veterinarian as soon as possible!
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 Cardiomyopathy
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 in one form or another. This is because if HCM is detected and arrested in its mild to moderate stages, then the prognosis for an essentially normal life for a number of years can be good. However, the form and severity of the disease at the time of discovery will ultimately dictate the prognosis in all cases. Additionally:
- 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.
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.