My maternal grandmother (whom I miss every single day of my life) died after a surgical procedure to help her heart. The odds of her dying were like less than 5%.
She died three days after my birthday. My mom before she passed told me that my grandmother actually coded on my birthday and mom told the doctor, "You absolutely cannot let her die on her only grandson's birthday." They got her stable, but she was too weak. I was at college and my mother had to come get me, because she didn't want me driving and didn't tell me what happened until we got home. My grandmother and I spend every Sunday afternoon together. We'd have lunch and then hang out watching TV. We did this for 20 years- every Sunday without fail unless I was at a school event; came home most weekends in college so I could have lunch with her.
Man I miss her.
All that to say, surgeries are always a risk. Especially as you get older.