Are heartworms visible?

Are heartworms visible? - Prestige Animal Hospital

Heartworms are not visible like other parasites, how people think, "Oh, I could see a worm on a fruit from a dog or a cat or something to that extent." No, they're not visible. They travel in the blood. The only way they're visible is with imaging, x-rays, and ultrasound. But otherwise, no, they're internal. They're inside the body.

Are heartworms visible? - Loch Haven Veterinary Hospital

No, heartworms are not visible in cats. They stay strictly in the heart or the lungs.