Dear Christopher Cat: During our cat’s last wellness visit, the veterinarian detected a heart murmur he hadn’t heard in the past. He recommended Gus, our 5-year-old cat, see a veterinary cardiologist, but we can’t afford that.

Our vet is concerned that Gus may have a type of heart disease called HCM and throw a clot that would cause a problem with his hind legs. How will we know if this happens?

Christopher Responds: HCM, or hypertrophic cardiomyopathy, the most common heart condition in cats, is associated with thromboembolism.

A thromboembolism is a blood clot that forms in the heart and travels through the blood vessels. In Greek, “thrombo-“ means clot, and “-embolism” means “to throw in.”

In cats, the clot often lodges at the junction where the blood vessels branch into the rear legs. Because of the location, this clot is called a saddle thromboembolism.

It blocks blood flow to both back legs, although sometimes one leg is more severely affected than the other. The lack of blood results in pain and diminished muscle function.

If Gus develops a saddle thromboembolism, he won’t be able to walk on his back legs and he’ll cry in pain. His hind paws will be cooler than his front paws, and his hind pads will be paler than his front pads.

This condition is so painful that it is essential to get Gus to your veterinarian or an emergency clinic immediately. Successful treatment of saddle thromboembolism is rare, so you should be prepared to make a difficult decision.