A thorough physical exam, performed by your veterinarian at least yearly (and ideally semi-annually in cats over 7 years of age) is paramount to picking up on subtle changes in your cat’s state of health. Auscultation, which means listening to the heart and lungs with a stethoscope, should be a central part of any physical exam.
Sometimes while listening to the heart we’ll hear a heart murmur. But what exactly does that tell us? The answer is a tiny bit complicated, so here are 6 questions that should be answered in order to help put the puzzle together.
Just what is a murmur anyways?
A murmur, simply put, is a “whooshing” sound that is heard when listening to the heart with a stethoscope. It usually means there is a problem with the heart that’s causing the blood in it to flow abnormally. Sometimes the word “laminar”, which means an orderly flow in something like layers, is applied to the way that blood is supposed to flow through the heart and its vessels. A murmur is heard when there is “turbulent”, or disorderly flow, thorough the heart.
Various disease processes can produce a murmur. Usually those diseases typically have to do with the heart, but they can involve other parts of the body (more on this later). In cats the most common heart disease is something called hypertrophic cardiomyopathy, also known as HCM. In this disease the muscle tissue of the left side of the heart enlarges, and because of this the blood flows abnormally through the heart.
How fast was the heart beating at the time?
Even if your cat appears outwardly calm at the vet clinic, most of them still get a little stirred-up by the whole process, and their heart rate can become quite elevated. A normal heart rate for a healthy cat is between 150 and 180 beats per minute, but we’ll often count 200 and greater in a normal cat that’s being examined at the clinic.
Sometimes we’ll hear a murmur in a normal cat with a very high heart rate, but we won’t hear it when the heart rate is normal. This may or may not signal a problem, and it’s critically important to consider further diagnostics to look for more concrete signs of heart problems, such as chest x-rays, when this occurs. Murmurs that are persistent despite heart rate should always be investigated.
How old is your cat?
In very young kittens, a heart murmur may be “innocent”, meaning that it resolves as the kitten ages and development completes. There is a hole between the two sides of the heart at birth, and sometimes there is a little bit of abnormal blood flow through that hole until it seals itself shut.
But in general, your vet should not be able to hear a murmur in your kitten after 3 – 4 months of age. If the murmur is still there at the time, it may very likely indicate a congenital (birth defect) problem with the heart or the circulation than must be investigated and treated, if possible.
What breed is your cat?
While heart disease can occur in any breed and in mixed breed cats, both Maine Coons and Ragdolls are known to carry the gene for HCM. If you’re considering purchasing a Maine Coon or Ragdoll kitten, you should specifically inquire about whether the breeder you are working with attempts to screen breeding cats for this disease. Echocardiography, or ultrasound examination of the heart, is often done to look for signs of the disease, but sometimes the disease is not detectable until the cats are past breeding age, and thus after attempts at detection are made. The gene mutation that causes HCM in Ragdolls has been identified, and a blood test exists for the disease in that breed.
Does your cat have any symptoms of heart disease?
Cats with heart disease can develop heart murmurs long before they become clinically ill with heart disease. Being sick because of heart disease is known as heart failure, and in cats this usually manifests as fluid occupying the chest cavity (pleural effusion), fluid occupying the lungs (pulmonary edema), or fluid occupying the sac that contains the heart (pericardial effusion).
To the casual observer, these complications produce lethargy (sleeping more), an increase in respiratory rate or increased abdominal effort associated with breathing, and cold limbs due to poor circulation. Because many of these problems don’t develop for years after a murmur is heard, it’s important to investigate the cause of all persistent murmurs, in order to determine a treatment plan and prognosis.
What does the blood work tell us?
A cat can have a heart murmur without heart disease being its primary problem. The most common example of this is the hormonal disease hyperthyroidism, which is very commonly diagnosed in middle aged and older cats. Hyperthyroidism results when there is too much thyroid hormone produced, and the body is persistently in an excessively “ramped up” metabolic state. One of the consequences of this is that the heart continually beats much faster, which ultimately leads to the development of HCM.
Cats with a heart murmur, but especially those with weight loss and GI problems like vomiting and diarrhea, should be tested for hyperthyroidism. This disease is treatable in several different ways, and the good news is that if the hyperthyroidism is controlled, the heart disease often improves substantially.
Cats that are severely anemic will also often have a heart murmur, because there are so few circulating red blood cells (relatively speaking), and this contributes to abnormal flow of blood through the heart. We might suspect severe anemia based on pale gums, but blood work will confirm it. Getting to the bottom of what is causing the anemia is critical, and resolving the anemia will cause the murmur to resolve as well.