My father had undergone angioplasty with 4 stent over a year ago. He is regularly undergoing follow up checkup and taking medications. 2 months back was his regular checkup where his reports like ECHO, ECG, Lipid profile, etc were normal. However he sometimes feels mild Chest pain. But today after doing a heavy outdoor work he felt chest pain which was alleviated after having sorbitrate 5. Should it be concerning as his reports were all normal few months back.