Hi, My Dad Having Heart Surgery 8 Years Back. After

hi, my dad having heart surgery 8 years back. After surgery he is still suffering from chest pain. few weeks back dad went through some check ups and it discovered he is having blockage in another right artery. then as per doctor suggestion we decided for angioplasty. he get discharged after 3 days as his body is performing well. but after 15 days he is feeling great weakness, he dont have chest pain now. but his strength level goes down. please suggest me some suitable solution as m too worried.