What Is The Life Expectancy With 75% Working Condition Of Heart?

Hi Doctor My father is 60. He has had 5 minor heart attacks (4 last year). He has been told that 25% of his heart is not working. He is currently on various tablets for his heart. Every so often, he has an angina attack. From this information, what do you think about his survival rate, comparing it to others in a similar condition?