died of heartworm because he wasn't treated. He was rescued (with ruptured eyeball) from a feral family when he was a wee boy and may have been exposed early in life. He was an indoor-only cat after his eye was removed as the vet was never sure how much vision he had.
He started having what we thought were seizures and she took him to the vet 2 or 3 times in the months before his death. The vet always said "cats usually don't have seizures" and all of his lab work was normal. I started videoing his last "episode" where he appeared to be having another long, continuous seizure. He went out on the screened porch and just fell over and died. It was heartbreaking to watch him in such distress. A vet friend looked at the video and said she though it was from heartworm.
Since Stevie died, we have applied Revolution regularly to all of our cats. Mosquitoes can get into your house and even if your cats don't go outside, they need the protection from heartworm.