Just like humans, the hearts of our pets are often one of the first things to wear out. Hypertrophic Cardiomyopathy is the most common form of heart disease in cats. In this condition, the muscular walls of the heart become too thick. This reduces the space in the heart chambers and causes the muscles to stiffen, both of which lead to less blood being pumped around the body. Treatment for this condition is possible; if an underlying cause for the disease can be found, in some cases, the changes can be reversed.
What causes Hypertrophic Cardiomyopathy?
The underlying causes for Hypertrophic Cardiomyopathy are varied and in many cases, nothing obvious is identified. However, the most common triggers are Hyperthyroidism and Hypertension (High Blood Pressure). Some cat breeds are genetically predisposed to the condition, particularly the Maine Coon and Ragdoll.
What are the symptoms of Hypertrophic Cardiomyopathy?
Cats are very good at hiding the symptoms of heart disease, which makes catching it, especially in the early stages, very challenging.
The reduced output from the heart means that they are able to exercise less and will tire more quickly. So, they simply rest and sleep more, which is often what we expect of them anyway! This means we have to be vigilant for more subtle symptoms, like an increased breathing rate when they are relaxed and panting when they do exert themselves. They might faint or collapse, but this is unusual.
Your vet may be able to pick up abnormalities when they listen to the heart with a stethoscope. These can include murmurs (where a whooshing sound can be heard in addition to the lub-dub drumbeat of the heart), a change in the rhythm, an increase in the heart rate or a change in the sound of the heartbeat. However, sometimes even if it is affected with Hypertrophic Cardiomyopathy, the heart can sound normal.
The abnormal flow of blood in the heart may cause clots to form. These can travel round the body and become trapped in the arteries, most commonly the ones feeding the hind legs, which cuts off the blood supply. This is called an ‘Aortic Thromboembolism’ (ATE) and sudden lack of circulation is very painful. The cat will often cry out, be very distressed and unable to walk. If it occurs, you must call your vet immediately.
How is Hypertrophic Cardiomyopathy diagnosed?
Commonly performed diagnostic investigations include blood tests, blood pressure monitoring, an ultrasound examination of the heart, chest X-rays and ECGs (an electrical trace of the heartbeat). Blood tests will highlight any potential underlying causes; an ultrasound allows your vet to look directly at the heart, measure the thickness of the walls, the size of the chamber and how well it is contracting; X-rays can show fluid build-up in the lungs; and ECGs are helpful in picking up any rhythm abnormalities.
How is Hypertrophic Cardiomyopathy treated?
First, if any underlying problems have been found, such as Hyperthyroidism or Hypertension, your vet will want to treat those. If they can be controlled, sometimes it is possible to reverse the changes in the heart muscle and normalize the condition.
Drugs that are often used to treat the Hypertrophic Cardiomyopathy itself include:
Beta-blockers - These slow down the heart rate, giving time for the chambers to fully fill with blood and also allows the muscle walls to relax as far as is possible. It also allows more time for blood to flow into the heart muscle itself, reducing its need for oxygen and encouraging it to work more efficiently.
Diltiazem - This does a similar job to the Beta-blockers.
Aspirin - This reduces the chances of blood clot formation and thus the occurrence of an aortic thromboembolism (ATE).
Diuretics - In some cases, the poor heart function can lead to fluid build-up in the lungs and diuretics are used to move this away and improve the breathing of the patient.
Your vet will always listen to your cat’s heart and give it a full physical examination at every routine check-up, which is why it is so important to keep to your regular appointments. However, if you are concerned about your pet, simply book them in for a consultation and your vet will be able to tell you if there is a problem.