My Abyssinian Red, Luca, died after 7 years and 2 days.
I explained the situation to the vet and he said it was presumed to be a heart attack.

るか Luca (アビシニアン レッド Abyssinian　Red, male ♂ ;January 16, 2017January 18, 2024)

8:45 Behavior that appears to be seizure.
8:46 Lying down in front of the door.
8:49 Start artificial respiration and cardiac massage.
8:56 Respiration, pulse, and heart stop and do not return. Loss of light reflex.
9:00 As soon as the veterinary hospital opened, we contacted the veterinary hospital and informed the director of the symptoms and current condition, and he said that he guessed it was heart.