What are the complications of heartworm disease in cats? - The Waggin Train Veterinary Clinic

Respiratory issues—again, being a more serious condition in cats and how it normally presents, I guess you could say similar to dogs, it takes fewer worms to cause these. That's the most common thing that I see. A cat that might come in for hacking, coughing, maybe even open mouth breathing, or perhaps poor color. Maybe the cat was running around playing or just jumping around a typical day, and all of a sudden just collapsed, acute collapse. It usually presents as either cardiovascular or respiratory signs in a cat.

Every once in a while, you'll see vomiting, although I personally have not seen a cat come in for vomiting and then later be diagnosed with heartworms. It's always been the respiratory signs that I have picked up on.