Heart Disease in Cats: A Silent Killer

Last week, a client brought her senior cat to have a pre-anesthetic blood test drawn by one of my certified veterinary technicians for a future dental procedure. Unexpectedly, this client also brought her recently adopted handsome young cat, named Apollo, for a nail trim. Since Apollo was a new patient to our clinic, my technician recommended a complete physical examination before the nail trim. Without any hesitation, the owner elected to have Apollo examined by one of my veterinary associates.

While Apollo was awaiting his examination, he let out a blood-curdling scream while sitting on my client’s lap. Only a few feet away, my technician raced back into the room to find a non-responsive cat in my client’s arms. My technician scooped Apollo up and immediately took him to our treatment room where we started cardiopulmonary resuscitation. After 15 minutes of aggressively trying to revive him, we regrettably could not resuscitate him.

Heart disease in cats is a life-threatening medical condition. Tragically, in some cats it can be a silent killer. At least once or twice a year, one of my feline cat owners will come home to find their supposedly “happy and healthy” cat suddenly limp on their floor. Unlike most dogs with heart disease, many cats with heart disease show no symptoms: no cough, no lethargy and no decline in appetite. Some may show subtle signs of increased respiratory rate (greater than 30 breathes per minute at rest) or greater abdominal effort with each breathe but these changes frequently go unnoticed by even the most observant cat owner. In the midst of a cardiac crisis, these pets will have labored breathing, pale mucous membranes, profound weakness, severe pain, and /or may experience numbness in their limbs

Who is at risk for developing heart disease?
Any aged cat and breed is at risk for developing heart disease but it is unlikely to be seen in cats less than 6 months of age. According to a number of studies, 16% of all apparently healthy cats have heart disease.

In the Maine Coon and Ragdoll breeds there is an inheritable, genetic mutation that predisposes them to heart disease. If you own either breed, ask your veterinarian if it would be advisable to test your cat for this mutation. In the future, I anticipate geneticists will discover other mutations responsible for heart disease in other breeds of cats.

How does one diagnose heart disease in cats BEFORE they have a crisis?

1. A physical examination by your veterinarian is essential but no guarantee that your pet is free of heart disease. Using a stethoscope, your veterinarian may detect a heart murmur (an audible turbulence of blood flow in the heart) or an irregular rhythm of heartbeats. Regrettably, the absence of a heart murmur does NOT mean heart disease DOES NOT exist – for only 50% of cats with heart disease have a heart murmur. An irregular heart rhythm is more consistently recognized in pets with heart disease. However, there is a 50% chance that your cat with a heart murmur has heart disease and it should be investigated further.

2. Radiography of the thorax (chest) is a quick, non-invasive diagnostic test that can be performed in almost every veterinary clinic. A thoracic radiograph provides meaningful information about the overall size and shape of the heart, as well as the character of the lung tissue. Unfortunately, the sensitivity and specificity of this tool for heart disease is not as great as we would like it to be. In the most common heart disease in cats, called Hypertrophic Cardiomyopathy, the walls of the heart are thickened, the interior chamber size is reduced, but the overall heart size may appear normal on the radiograph especially in the early stage of this disease.

3. The Cardiopet pro-BNP Test by IDEXX Diagnostic Laboratory is a screening test for heart disease in cats. This blood test measures the NT-proBNP hormone that is released by stretched or stressed muscle cells in the heart. The rise in the level of this hormone is proportional to the abnormal stretching and stress of heart muscles. This test has an 85% sensitivity for detecting heart disease in cats. False positive and false negatives do exist with this test. Non-cardiac patients with hyperthyroidism (overactive thyroid gland), hypertension (high blood pressure), or/and kidney disease can have elevated NT-proBNP levels. Cats with elevated levels of this hormone should have a cardiac ultrasound to verify the diagnosis of heart disease.

4. A Cardiac Ultrasound is the gold standard for diagnosing and staging heart disease in cats.
If a heart murmur or an irregular heart rhythm is detected in a cat, I strongly recommend a veterinary cardiologist perform a cardiac ultrasound. The good news is that 50% of apparently healthy cats with heart murmurs have normal cardiac ultrasounds. So having a heart murmur is not necessarily a death sentence for your cat – but just a warning light that there may be a problem.

Unfortunately, a single normal cardiac ultrasound does not eliminate the possibility of heart disease to develop in the future. For high-risk breeds, like Ragdolls and Maine Coons, and cats with heart murmurs that may vary in intensity over time, your veterinarian may recommend periodic repeat cardiac ultrasounds.

Cats are very secretive and easily hide their illnesses from their owners. Apollo’s death reminds us all about the fragility of life, to appreciate good health, and enjoy the time we have together. Although we cannot cure heart disease in cats today, it can be medically managed to extend your pet’s quality of life. Please don’t forget to schedule your pet’s annual physical examination appointment with your veterinarian so your cat can live its’ best life.

Dr. Donna Solomon is a veterinarian at Animal Medical Center of Chicago and invites you to email her your questions or future topic ideas to [email protected]

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