Has your cat been diagnosed with hypertrophic cardiomyopathy? Don’t panic. Hypertrophic cardiomyopathy (HCM) is the most common feline heart disease, and up to 15% of all cats may suffer from it. In fact, many cats with HCM will live long and healthy lives without ever being diagnosed or treated. However, for some cats, HCM can become a devastating disease.
What is Hypertrophic Cardiomyopathy?
Hypertrophic cardiomyopathy (HCM) is a disease that affects the heart muscle, or “myocardium." HCM causes the left ventricle of your cat’s heart to thicken, which decreases the space available for blood to flow. This means that a smaller amount of blood is pumped through your cat’s body with each heartbeat compared to a healthy cat. In order to compensate, HCM cats have an increased heart rate (tachycardia). Tachycardia and heart rhythm abnormalities can be a clue that your veterinarian should test your cat for HCM.
Hypertrophic Cardiomyopathy Complications
Although some cats with HCM will only have an abnormal heart rate, other cats will go on to develop further symptoms of this progressive heart disease. Your cat’s increased heart rate may only be a temporary solution to the blood flow problem. As your cat’s heart rate increases, he will also need a higher supply of oxygen, which might outpace what his small lungs can supply.
Without enough oxygen, the tissue in your cat’s heart muscle will begin to die. And without a properly functioning heart, your cat could experience heart failure or fluid accumulation in the lungs. This fluid build-up (pulmonary edema and/or pleural effusion) will cause your cat to have difficulty breathing. Eventually, a blood clot could develop in the heart (thromboembolism) and block a blood vessel when it gets pumped through the body. The final stages of hypertrophic cardiomyopathy include limb paralysis, severe pain and/or heart failure.
Hypertrophic Cardiomyopathy Treatment
Although there is no current cure for feline hypertrophic cardiomyopathy, there are ways to stop it from progressing. Your veterinarian will help you determine the appropriate interventions to delay or prevent HCM from moving to the next stage. Depending on your cat’s conditions, treatment may include controlling your cat’s blood pressure, relieving heart congestion, blocking fluid buildup around the lungs, and/or preventing thromboembolisms. With early diagnosis and proper treatment by a veterinarian, your HCM cat could still live a long and healthy life.
How do I know if my cat has HCM?
Your veterinarian may test your cat for hypertrophic cardiomyopathy if he has an increased heart rate, heart murmurs, lethargy and/or difficulty breathing. Also, certain cat breeds (like Maine Coons and Ragdolls) are known to be at increased risk for HCM and are recommended to be tested early. Your veterinarian will choose one of two ways to test your cat for HCM:
The first and traditional way to test for HCM is to screen the blood for chemicals like cardiac troponin I that indicate the disease is currently affecting your cat. However, this test may not catch HCM at its earliest stages, when treatment would be the most beneficial. A newer approach is to test your cat’s DNA for gene mutations that put your cat at increased risk for developing the disease, so that you can be prepared to treat your cat’s symptoms before they decrease your cat’s quality of life.
The Genetics of Hypertrophic Cardiomyopathy
Scientists have found that feline hypertrophic cardiomyopathy can be inherited, which means it’s passed through DNA to your cat from his kitty parents. We have only begun to identify the genes (there are many) that put your cat at high risk for HCM. Genes are the blueprint instructions for building cat (and human) bodies, and the genetic instructions for building a healthy heart will be most important in determining whether or not your cat will have HCM.
Scientists have only identified one of these genes so far: MYBPC3, a gene that is essential for developing heart muscle. Two different mutations in this gene (A31P and R820W) can be inherited by Maine Coons and Ragdolls. When these cats inherit the mutated genes from both parents, they have up to 18-times higher risk of developing complicated cases of HCM. Tests are already available to screen these breeds for the A31P and R820W mutations, but most cases of HCM in cats are still unexplained.
The Future of Hypertrophic Cardiomyopathy Treatment
Unfortunately, scientists have not paid much attention to cat genetics. It’s time for this to change. Cats and humans share more than 90% of the same genes, and hypertrophic cardiomyopathy also affects humans. If we can identify more genes responsible for this disease in cats, it will help us address this complicated disease in humans as well.
By understanding genetics, we can develop specific drugs to help prevent this disease from progressing. Based on the one gene identified so far (MYBPC3), scientists have created a drug that helps some HCM cats increase the blood flow out of their hearts. These gene-specific drugs will have fewer side effects and could one day potentially reverse this disease. In the future, genetic tests can be used to help you determine whether your cat will have a harmless or life-threatening case of HCM, and which interventions will be most successful at helping your cat live a long and healthy life.
If your cat suffers from hypertrophic cardiomyopathy, he could help future cats with this disease by having his DNA sequenced and tested today. Basepaws offers a “cat scientist" discount price for cats suffering from this disease, to help scientists speed the identification and treatment of this disease. Contact us for more info. Please spread the word!