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Ask a Vet: How Can Cats Suddenly Develop Symptoms of Heart Failure?

Cardiomyopathy can evade vets' detection and show symptoms only when it's too late.

Dr. Eric Barchas  |  Mar 15th 2016


Many months ago I worked on a case that will haunt me for a while. A cat was brought to my office with a two-hour history of respiratory distress. I could tell within moments that the cat was not going to make it.

The cat was an 11-year-old Maine Coon mix. She lived indoors and had not escaped recently. She had not been exposed to any toxins, and she had not suffered any known trauma. She had been to the vet two months prior to her crisis, and she received a clean bill of health at that time. Earlier in the evening the owner had noticed that her breathing was abnormal, and the symptoms had gotten worse since that time.

By the time I met her, she was in serious trouble. Her chest and abdomen heaved with every breath. She stood with her neck extended and her nose up, and she breathed through her mouth. Cats breathe through their mouths only in desperation. Her breathing was raspy, noisy, and wet — it sounded like there was fluid in her throat.

There are two common causes of such severe respiratory distress: asthma and heart failure. With time, as a veterinarian, one gains an intuition about which one to suspect. This case had heart failure written all over it.

Photo of Dr. Eric Barchas by Liz Acosta

Photo of Dr. Eric Barchas by Liz Acosta

We immediately began oxygen supplementation, and a technician administered an injection of furosemide, a diuretic medication that treats heart failure. To definitively differentiate between asthma and heart failure would require X-rays.

But there was a problem. To take X-rays we would have to violate rule No. 1 for cats with breathing difficulties: Do not stress them. X-rays require cats to be in certain positions, and changing position can be very stressful and dangerous for a cat who’s having trouble breathing. X-rays were out of the question.

There was, however, an alternative: I performed a quick ultrasound exam. This technique (called a VetBLUE, which is short for veterinary bedside lung ultrasound exam), which did not require the cat to change positions, confirmed my suspicions. Ultrasound artifacts called B-lines, which indicate fluid in the lungs, were prominent in all of the lung fields. Wet lungs are not compatible with asthma, but they are a hallmark of heart failure.

We redoubled our efforts with the diuretic. An additional, high dose was administered. The cat voided a large quantity of urine — the medication was working, but the situation was too advanced for it to save her. The wet breathing noises she made indicated that fluid had accumulated in her major airways, and it is a sign of a severe situation. Cats with such massive fluid accumulation almost never survive — they drown in the fluid their own bodies produce. Sadly, this cat was not an exception.

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Intensive care pet unit by Shutterstock

The owner was beside herself. Was the heart failure the result of the lifestyle that the owner had provided? Had it been caused by diet? Could the crisis have been prevented at home? How could she have received a clean bill of health two months before the crisis? And how had things gotten so bad, so very fast?

The answers to the first three questions were no, no, and no.

Most heart disease in cats is caused by a condition called cardiomyopathy. Cardiomyopathy is a problem in which the muscle of the heart does not function properly. It is a hereditary condition, and Maine Coons are highly predisposed to it. Unlike human heart disease, it is not linked to exercise or lifestyle choices.

In the past, many cats died of cardiomyopathy because their diets contained insufficient quantities of an essential amino acid called taurine. Once the link between taurine and cardiomyopathy was discovered, all commercial cat foods were supplemented with taurine. Diet-related cardiomyopathy is very rare now as a result. The cat in question received a high quality commercial food. Diet had not caused her problems.

The crisis could not have been prevented at home — it came on fast, and it was not precipitated by anything that the owner or cat did. And I’m not surprised that the cat received a clean bill of health two months before the crisis. Cardiomyopathy does not consistently cause any irregularities (such as a heart murmur) that can be detected on a physical exam.

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Food and other lifestyle factors play no role in many cases of feline heart failure. A Russian Blue cat eats food from a can by Shutterstock

However, although the cat’s previous physical exam was normal, it is certain that she was suffering with cardiomyopathy at the time of the exam. This brings us to the owner’s last question: How did everything happen so fast?

Many crises related to heart disease in cats occur as a result of decompensation. Cats’ bodies are remarkably good at adapting to disease. As a result, cats with chronic diseases often show no symptoms as the disease progresses. They may go months or years without any symptoms. Ultimately, the pathology reaches a point beyond which the body can no longer compensate. At that time, everything falls apart at once. The cat appears to get sick suddenly, when actually what is happening is the sudden manifestation of a long-standing problem.

In fact, the first sign of heart disease in cats may be a crisis like the one I have described. Other cats may experience an incredibly painful blood clot in their hind legs as the first symptoms. For some cats, sudden death is the very first sign of heart disease.

I felt truly sorry for the cat’s owner. I look forward to the day when medical science gets the better of cardiomyopathy.

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