How much cardio for healhty heart per day?

I will recommend to : Get a doctor evaluation before starting aerobic exercise. Build yourself slow. Calculate mhr(roughly 220-age). Start, keeping 75%of mhr and build yourself up to 85-90% to build your indurance and cardio health. 30 min to 45 min 5 times a week will be great to start. Do alternate slow/resting 70% and up 85-90% increasing highs slowly but always resting state.

It all depends: On how healthy you are, how we'll you can moderately exercise without shortness of breath or chest pain. If you need to lose weight then you need a minimum of twenty minutes per day.