Heart problem. Treatment advice on this.

Dear sir, My father is 66 year old and he got mild attack 20 years back, he was admitted in hospital for 1 month and completed the treatment, and he didn't have any issues till age of 64, recently he faced high heart rate about 200+ heart beats at this time he is getting very tierdtired and nausea and vomiting not able to take water also. When we checked doctor they said his heart has scar in valve chamber due to the earlier attack. Now the blood not flows in one chamber correctly. Also they said his heart functions only 30% hence surgery not possible. We don't know what's the issue how to treat this for permanent cure. Dr suggested him to take medicines ( cardiovas, antrovasti, ecosprin etc...) for life-long with diet restriction ( no oil, no coconut) This happened 3 times in this 2 years. I need your valuable assistance and treatment advice on this.