Getting eaten sucks, heart attacks suck, so why does the spider do this? No one will ever know.
That spiders heart is especially weak, an that is why it has that trouble.
It's very fragile an scares easily, but it has a regular spider heart.
It just can't cope with stressful situations.
It forces the heart attack as suicide, because it thinks: "It's better than crunch time".
Getting eaten sucks, heart attacks suck, so why does the spider do this? No one will ever know.