I don't know specifically but they frown upon having astma on your records even if you've been free of it for over ten years so I assume a hole in the heart wouldn't go down too well. But like FindFixStroke said everyones assessed individually.
gettin a hole in your heart generally see's you booted out but normally thats something to do with being dead! you'll be assessed and maybe accepted however if you fail phase 1 they'll boot ya unless your going RLC where no-one has a spine let alone heart nowadays! (old and bold chill out! it's your sprogs that are a joke!)