Small Animal Services: Feline Hypertrophic Cardiomyopathy
Feline Hypertrophic Cardiomyopathy
What is Hypertrophic Cardiomyopathy?
Feline Hypertrophic Cardiomyopathy (HCM) is a common heart disease, affecting up to 15% of all cats. HCM causes thickening (hypertrophy) of the left ventricle in the absence of a known cause, such as high blood pressure or an overactive thyroid. HCM is caused by genetic mutations in Maine coon and Ragdoll cats, and genetic causes may also be present in other cats. In HCM, the heart muscle is predisposed to abnormal relaxation and contraction. These abnormalities can lead to atrial enlargement, congestive heart failure (CHF, fluid in the lungs), fainting, and blood clots.
How is HCM diagnosed?
Screening for HCM can be challenging. Your veterinarian may recommend further evaluation of any abnormal heart sound by echocardiography (ultrasound of the heart), but many cats with heart
murmurs are normal, and many cats with HCM have normal heart sounds. Your veterinarian may also use a blood test called NT-proBNP to assess the need for echocardiography.
The diagnosis of HCM requires accurate echocardiographic measurements to determine the ventricular wall thickness, and to determine the left atrial size. Depending on your cat’s age, general health, and echo findings, additional tests may be performed (e.g. blood pressure, thyroid evaluation, chest x-rays, electrocardiogram or genetic testing).
What is the treatment for HCM?
The early stages of HCM may not require treatment for years. Your cardiologist will evaluate many factors affecting your cat before making recommendations. Left atrial enlargement and some rhythm disturbances increase the risk of blood clot formation (thromboembolism), and cats with severe
left atrial enlargement often take clopidogrel to reduce their clotting risk. Other medications are also sometimes used (sometimes in addition), cats on these medications should stay indoors. CHF caused by HCM requires additional medications, often including furosemide, ACE-inhibitors (e.g. enalapril or benazepril) and pimobendan. Some cats require hospitalization to treat heart failure.
How is HCM monitored by my veterinarian and cardiologist?
Monitoring a cat with HCM depends on the severity of their disease, and the nature of the cat. Mildly affected cats that are not stressed in the hospital will most commonly be monitored with annual echocardiograms. Cats that have experienced a complication of CHF or thromboembolism are commonly monitored with bloodwork and x-rays every 3-6 months however, the frequency will depend on a variety of patient factors.
How can I tell how my cat is doing at home?
Monitoring the breathing rate when your cat is sleeping can help detect early signs of CHF. The rate should be less than 36 breaths per minute when your cat is sleeping, and rates above 40 should prompt evaluation by a veterinarian. A smartphone app called Cardalis simplifies tracking the
breathing rate. Blood clots (thromboembolism) cause the sudden and very painful loss of blood flow to the affected area, most commonly the rear limbs. Sudden, painful loss of leg function (paralysis or lameness) should prompt emergency evaluation.
What is the prognosis with HCM?
Some cats with HCM will not develop signs of the disease, and live normal lives. Regular monitoring helps detect disease progression that warrants medication. In one study, 20% of cats developed CHF within 5 years of diagnosis, and 9% experienced a blood clot during that time. Once a cat is diagnosed with CHF survival is variable, with an average of about 12 months with medications.
Close monitoring and communication with your regular veterinarian and cardiologist provide the best chance possible for your cat to feel good during this time.
The NC State Cardiology Service supports numerous research projects aimed at building on what is already known about heart failure and at uncovering new knowledge about its causes, diagnosis and treatment…
Veterinary Cardiac Genetics
Are you interested in learning more about cardiomyopathies, (diseases of the heart muscle)? DNA testing is available for the following breeds: Feline HCM (Maine Coon, Ragdolls), or Canine cardiomyopathies (Boxer, Doberman.)
The NC State Cardiology service now offers a Holter (24 hour ambulatory ECG) program.
Go to the Cardiology Clinical Studies page for information on current clinical studies. Details include the study’s purpose, benefits for participating, and financial incentive information.
Hypertrophic Cardiomyopathy in Cats
Hypertrophic Cardiomyopathy (HCM) is the most prevalent feline cardiac disease. It is a primary disorder of the heart muscle characterized by thickening of the left ventricle. Learn more here…
Frequently Asked Questions & Resources
We operate primarily on a referral basis, with the patient’s primary veterinarian referring them to the NC State Cardiology Service by calling us to discuss the patient’s condition.
Referral is not required for second opinions, breed-related certifications for congenital heart disease, or treatment of heartworm infection. By speaking with the primary veterinarian prior to the appointment, we are often better able to determine the severity of the problem, which of our services the patient is likely to need, how soon the patient needs to be seen, and whether any of the other specialty services at the VH should be consulted. We will also discuss our policies and fees at the time the referral is made, and formulate a plan for communicating our findings to the primary veterinarian.
After the referral has been made, owners may call us to make the appointment. We will collect owner and patient demographic information, provide an estimate of charges, discuss some of the diagnostic procedures that may be required, and answer any questions the owner may have regarding the visit. In order to have the best chance of getting a complete diagnostic work-up done in one day, we try to schedule new patients in the morning between 9:00-10:30 every day except Thursday which is reserved for interventional cardiac catheterization or other semi-elective surgical procedures.
The average total cost for some uncomplicated common interventional procedures that we perform routinely are as follows:
- Pacemaker implantation (includes EMG workup): $2800-3000
- Balloon valvuloplasty (includes workup): $2800-3000
- Patent Ductus Arteriosus occlusion (includes workup): $2500-2800
- Heartworm Retrieval (canine/feline): $2200-2500
Information Needed for Initial Evaluation
- Brief description of the reason for the appointment with the Cardiology service, including all of the patient’s symptoms even those that may not seem significant.
- List of medications patient is receiving, including any over the counter drugs, herbs or metabolic supplements, as well as any problems the patient may be having with the medications.
When am I going to see a doctor?
Please note that our Interns and Residents (aka House Officers), are fully licensed doctors with the same education and credentials as a general practitioner. There will ALWAYS be a doctor in charge of and supervising all aspects of patient care at the VH. In many cases multiple specialists may consult on a patient should their expertise be required. Typically, a fourth-year student will first collect a detailed history and present this information to the doctor in charge. You will then have an opportunity to discuss things in detail with the doctor and together you and he/she will formulate a diagnostic and treatment plan.
My doctor introduced him/herself as an Intern or a Resident – what does that mean?
It is important to understand that every intern or resident at the VH is a fully licensed doctor with the same education and credentials as a general practitioner. Interns and residents have chosen to pursue additional, in-depth postgraduate clinical training and were selected by us in a highly competitive international application process. We think you are in great hands!
Examination: Generally, a 4th-year veterinary student will escort the client and patient into an exam room to take a complete history while they perform a physical examination on the patient. This will take approximately thirty minutes.
Review: The student will then leave the room for about fifteen minutes to consult with one of our faculty cardiologists. At this time, the student and the cardiologist will also review any diagnostic material that the referring veterinarian has sent. The cardiologist will then introduce him or herself to the client and examine the patient. New patients usually need to be left with us for the day to allow enough time to complete the diagnostic tests needed to evaluate the heart and cardiovascular system.
Diagnostic tests for patients suspected of having heart disease often include electrocardiography, echocardiography, radiography, and various blood tests. Patients may need to be lightly sedated to complete the evaluation, since several of these tests require the patient to be absolutely still for several minutes at a time.
Discharge: At the time of discharge from the hospital (usually between 4PM-6PM), the cardiologist will discuss the patient’s condition with the owner and answer any questions. We will also send home detailed written information about the physical findings, diagnostic test results, diagnoses, medications, and recommendations for ongoing care. A copy of these instructions will be faxed to the referring veterinarian.
While a patient is hospitalized, the cardiologist and student on the case will arrange mutually convenient times every day for the owner to call (or be available to be called) to get an update on the patient’s condition, and answer any questions that may arise. We will also arrange mutually convenient times for the owner to visit the patient, if desired.
You are a State facility, so why are your fees so high?
The VH is a not-for-profit health care center and receives less than 2% of operating costs from the the State of North Carolina. The majority of our operating costs are paid by client fees and donations. In fact, many of the state-of-the-art diagnostic and treatment options we offer are only possible because of generous gifts from our clients. Our fees are set to cover the balance of our operating costs, and we are always looking for ways to provide better service at lower cost. Total costs are comparable to those of veterinarian specialists in private practice.
If you do not have a primary veterinarian you can search for one here: North Carolina Veterinary Medical Association
Additional resources may also be found at the NC State College of Veterinary Medicine’s website.