Nah, i'll take the small dog breeds.. Even if my dog attacked someone trying to help me live he probably wouldn't break skin and would be tossed across the room for good reason.

Back in the day when we did a lot of residential boundary surveys we would have to get into yards where the home owner was at work and left there dog out. A co-worker was deathly afraid of dogs therefore had nothing but hatred for them. Me I grew up with dogs and could usually reason with any dog. I do believe they sense a fear in humans. Dogs just took an aggressive posture and behavior when he was near. Me on the other hand could talk calmly and have them wagging tail and running around with toys shaking ready to play.

Now little dogs are the ones for me to be wary of those lil ankle bites like to creep up when you turn back. Miniature schnauzers are a good example. And Chows while not small are a keep your distance and show respect animal. I dont know if they keep records on such things but I would bet a Chow is high up on the dog bite scale.

So, what happens when you have a heart attack and can't remove the dog from the situation?

That's the issue here, not whether or not they behave when you're around. It's what they do when you aren't in control that's the problem.