It's a timescale thing more than up to 4000% more death kinda thing. It might be like getting limescale in a kettle. Once it builds up on the element too much you have to throw it in the bin, but you don't know where the deposits will build up first. Maybe in the people that die quickly, the shot gets sucked into their heart faster because they have cholesterol smothering the inside of it first, so it clings on easier.