There was discussion of this on Fox News, I cannot remember if it was Dr. Badin or another doctor, I've seen so much about this story, but they said that the poison the barb emits isn't really that deadly, but pulling it out may have caused more damage as the barb has small hook like projections on the sides, much like a fish hook. There is no way to truly know, but pulling out may have caused more tearing & caused more bleeding into the pericardial sac.
Of course, they also said that pulling an object out, would be a knee jerk reaction, not one that one would think about.
Unfortunately, when the barb is attached to a 220lbs Sting Ray, which is moving around violently, there is no good option. I don't think anyone has said that the blade broke off the fish. Therefore its an academic discussion. In any event, if it went all the way through his heart, his reaction made no difference to the final result. At least he did not linger and suffer unnecessarily...
Its a week later and I still can't get this story out of my head....as a Dad of similarly-aged children all I can think about are his kids...