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Published on December 7, 2016
Heart disease is common in cats. Unfortunately, disease can be present even in the absence of a heart murmur or any other specific symptom detectable on a cat’s routine physical exam.
In many cases, a crisis event is what brings you to the veterinarian. Suddenly your cat is not eating, having difficulty breathing or is acutely painful. That’s when we discover underlying heart disease.
Cat breeds with increased risk of heart disease
While congenital heart defects do occur in cats, they are rare, and cardiomyopathy (disease of the heart muscle) is responsible for most diagnosed feline heart disease.
By some estimates, 30 percent of pet cats may be affected and the majority of these are mixed breed cats. Purebred cats like the Maine Coon, Ragdoll, Persian, Siberian and Norwegian Forest Cat have a high incidence of heart disease in their populations, and the responsible genetic mutation has been tracked in the Maine Coon and Ragdoll breeds.
In mixed-breed cats, the disease is more common in young adult males.
Most common type of feline heart disease
Hypertrophic cardiomyopathy is the most common type of cardiomyopathy seen in cats today. In HCM, the muscle of the left ventricle increases dramatically in size and thickness. This causes decreased elasticity and slower relaxation by the heart chamber during filling and contracting.
Pressure builds up in the left ventricle causing backflow to the atrium, and the sluggish blood flow sometimes allows large blood clots to form. The thickening of the muscle also distorts the heart valve, and may push it into the way of blood trying to leave the heart, creating an obstruction.
Heart murmurs warrant further screening
A murmur is an abnormal heart sound created when there is unusual turbulence in blood flow caused by leaky heart valves or obstruction. There are many causes for a murmur in your cat. Cats can be born with a heart defect, while anemia, fever and other metabolic disease may cause a temporary murmur.
Only about a third of cats with murmurs actually have cardiomyopathy, but finding a heart murmur on a routine exam can be a lucky tip-off, allowing us to diagnose heart disease before a crisis. A murmur warrants screening bloodwork and a blood pressure measurement to look for non-cardiac causes.
A proBNP level measures the presence of enzymes released by damaged heart muscle, and while there can be false positives, it is a good screening test for cardiomyopathy. X-rays may be helpful, especially if a patient is having trouble breathing, and an ECG may be indicated if an arrythmia is heard.
Referral to a veterinary specialist
The best procedure to assess heart function is the echocardiogram, an ultrasound examination of the beating heart. This test can be diagnostic for heart defects, neoplasia and cardiomyopathy, and since we can visualize exactly what is abnormal about how the heart is working, it helps us select appropriate medications.
Most of the time, an echocardiogram requires referral to a veterinary cardiologist.
Medications to treat heart disease in cats
A cardiologist will attempt to slow down disease by prescribing medicines to relax the blood vessels, so the heart does not need to pump as hard. Others medications can increase the supply of blood and oxygen to the heart, slow down the heart rate, or enhance the strength of heart muscle contraction.
Blood thinners may be prescribed to reduce the danger of blood clots.
Signs your cat is going into heart failure
When a diseased heart finally fails, fluid begins to build up in the lungs and chest cavity. Cats in failure lose weight because they eat poorly — it is hard to breathe and eat at the same time.
With increasing fluid, owners may notice faster more labored breathing, or even “open mouth” breathing. Cats may be unable to lie down comfortably, spending alot of time in the “Sphinx” position, crouched with their elbows out, which allows the largest chest capacity for lung expansion.
Because cats are very good at slowing down, owners may be unaware of any problem at all until they move households, have a canine friend come and visit, or take their cat to the veterinarian for annual vaccines. These stresses can trigger respiratory distress and be life threatening for a cat with heart failure.
The first goal of veterinary treatment is to provide oxygen and administer diuretic medication to pull fluid out of the chest cavity and lungs. If the patient can be stabilized and breathing improved, an echocardiogram should be performed to confirm the diagnosis and help choose cardiac medications.
Heart disease can cause blood clots and sudden paralysis
Cats with heart disease tend to form blood clots within the heart chambers, and sometimes pieces break free and lodge in the circulation. This can happen very abruptly and a cat that seemed normal moments before will suddenly cry in pain and appear partially paralyzed.
A “saddle” thrombus lodges in the fork of the lower aorta, causing paralysis and loss of blood flow to the back legs. Less common is blockage of the brachial artery, which causes paralysis of the front right leg. Affected limbs feel cold and may appear bluish.
Sometimes smaller thrombo-emboli can affect the brain, causing balance issues, confusion or other stroke-like symptoms.
If your cat has a thrombo-emboli causing paralysis, the prognosis for recovery is very poor. There is no effective treatment once loss of blood supply has permanently damaged the limb.
Detect and treat heart disease early
Cardiomyopathy is a common and very serious disease of pet cats. If your veterinarian detects a heart murmur, be proactive in finding out the cause. Be aware if you own a susceptible breed and consider a screening echocardiogram.
If your cat has cardiomyopathy, early detection and treatment gives your feline family member the best chance at a longer, comfortable life.