Can someone live near single 30 percent of their heart function?

They have all of their heart muscle but singular 30 percent of the normal 100% function, suffered a massive heart attach and then another.J/w
Answers:    I pinch it that the 30% is a fraction of the normal ejection fraction (EF). Normal EF is typically 60-70%, so 30% of that is roughly speaking 20-25% EF. So yes, people live with that low of an EF adjectives the time. If the 30% is referring to EF, then that's still pretty low, but somewhat livable, at least for a while.
My dad live 8 years next to only 30% of his heart. Quality of life wasn't what is be before his massive heart attack but he did manage to stay near us that long. The doctors told us he should have only lived 3. He died of congestive heart end. He was in and out of the hospital alot the end couple of years of his life with fluid building up. He in reality continued to work for about 3 of that 8 years. Yes! But the 30 percent will decrease and front to death.