Glad to hear things are looking up now, its a shock when something like this happens, got to admit, I have not heard of a dog attacking a bitch just because she is in heat? obviously I have hear of them being amorous but not vicious, there has got to be an other reason than this for the attack surely? and I agree, it dosnt matter if the owner was unaware that the dog was going to attack, they are responsible for their dog and any incidents involving that dog, this is all part of dog ownership, they should be responsible for the vets bill.
Mo