I have a good terrier with a weak heart. She’ll die early.
She’s still young, just four, and her condition isn’t apparent unless she’s playing hard at fetch or chase the hose water. When it gets her, she stops, lies down, rolls over, breathes, and waits. It’s syncope — the light headedness you feel when you stand too fast. Her heart can’t keep pace with her legs and her lungs and eventually there isn’t enough blood to her brain. When she was a pup it would sneak up on her while she romped — Boom, and over she went. She’s older now and feels it and puts herself down and settles into the grass, breathing, waiting.
When it passes, up she goes to her feet and she finds the frisbee again or the spray from the end of the hose. The game only ends when I get bored of it.