welcome to HealthcareMagic
Sorry i have to correct you and say that the arteries supplying blood are blocked and not the valves.One blood vessel is 100% and the other are 75-80 and one is better than the two so definitely if the blood supply to heart is reduced your father will have chest pain
so he will require treatment.The treatment is medical;Angioplasty
;and CABG that is bypass surgery
.The line of treatment will be selected by your fathers Cardiologist depending upon the symptoms he is suffering and his general condition.So please discuss the line of treatment with him as the Cardiologist will be the better person to advise you as he has seen the patient and knows general condition well.