No, 50/50 is not my chances of surviving. Actually we all have 0% of surviving. Everyone is going to die sooner or later.
I have two 50% blockages and one 40% blockage. 70% blockage is the thresh hold at which they will even consider a stent.
My heart rate is in the mid 40's. I guess it will last longer if I the the rpm's low, just like a automobile engine.