Understanding Hypertrophic Cardiomyopathy in Ragdoll Cats

HCM in Ragdoll Cats

A reader wrote in telling me her kitty suddenly passed of HCM.  She has asked that I re-run this guest post by Lorie Huston – may she RIP.

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Originally published Jul 26, 2012

The other day a Floppycats reader emailed me concerned that her kitten might have HCM, I did not have a good idea of what all it entailed.  So I reached out to Lorie Huston, DVM to see if she could provide insight for us.  Thank you to Lorie Huston, DVM for writing this  – please feel free to ask questions!

Guest Post by Lorie Huston, DVM

Hypertrophic cardiomyopathy, or HCM, is the most common form of heart disease seen in cats. In Ragdolls, most cases of HCM are inherited from the parents and caused by a gene mutation. Fortunately, we have DNA tests that can detect if a specific cat is carrying the mutation. Unfortunately, we don’t have a cure for HCM at this time, although medications are available that may help some cats.

Affected Ragdoll cats may inherit a mutated gene from just one parent (which is referred to a heterozygous) or a mutated gene from both parents (referred to as homozygous.) In Ragdolls, cats that are heterozygous tend to have a milder form of the disease than those that are homozygous although the disease can still be very serious even in heterozygous cats. (This varies in other cat breeds as the specific mutation and the means of inheritance varies from breed to breed.)

Hypertrophic cardiomyopathy affects the heart muscle, causing the muscle to become thickened, resulting in an inability to pump blood normally through the heart. In most cases, the left side of the heart is the most severely affected, leading to left-sided heart failure.

Symptoms associated with HCM include:

• Difficult breathing.
• Increased respiratory rate.
• Increased respiratory effort.
• Increased heart rate.
• Weakness.
• Lack of appetite.
• Lethargy.
• An irregular heart rate (arrhythmia) which may cause fainting episodes.
• Cyanosis due to lack of oxygen.
• Hind leg paralysis and/or pain due to a blood clot lodged in the aorta (aortic thromboembolism). In this situation, a blood clot breaks off from within the heart and travels through the aorta, becoming lodged at the end of the aorta blocking the flow of blood to the hind legs.

DNA testing can reveal whether your cat carries the gene mutation most commonly responsible for HCM. However, the only way to accurately evaluate how your cat’s heart is functioning is via an echocardiogram. Though the inherited heart disease caused by the gene mutation is the most common cause of HCM in Ragdolls, there are other causes as well. For instance, hyperthyroidism has been implicated in causing toxic changes within the heart that may cause cardiomyopathy. (Some cardiologists argue that these cases are not accurately referred to as hypertrophic cardiomyopathy but the symptoms are still similar.)

An echocardiogram is an ultrasonographic evaluation of your cat’s heart and allows direct visualization of the heart muscle and individual chambers of your cat’s heart. A cardiologist can measure the muscle thickness and determine whether your cat’s heart is pumping blood through its various chambers effectively and efficiently.

Most cats with cardiomyopathy will need to have an echocardiogram performed on a periodic basis to monitor progress of the disease.

There are a number of drugs that are used to HCM.

• Furosemide (Lasix) is a diuretic and is used to treat congestive heart failure by removing excess fluid accumulating in the lungs and other body tissues because of the heart failure. Another diuretic less commonly used is spironolactone.
• Enalapril and benazepril are ACE inhibitors (angiotensin-converting enzyme inhibitors). These drugs help HCM cats by causing vasodilation, or opening of the blood vessels, making it easier for the heart to pump blood.
• Pimobendan (Vetmedin) is a drug that causes both vasodilation and an inotropic effect which causes the heart muscle to contract with a greater force.
• Anticoagulants are often used in an attempt to prevent or control blood clots. Aspirin and clopidogrel (Plavix) are the two most commonly used anticoagulants.
• Cats with HCM may have elevated blood pressure also. Medications which lower blood pressure may be necessary and include amlodipine and atenolol.
• Supplements such as taurine, L-carnitine and coQ10 are sometimes used as well but their effectiveness is questionable.

Thanks again to Lorie for helping us understand HCM in Ragdoll cats!  Please join Lorie on her website – Pet Health Care Gazette