My Father had a angioplasty in Jun 2017. From last one month almost every week he is getting chakker, dry mouth, some time stomach pain, some time back pain, heavy head, shortness of breath and he feel like is is going to die now. it last for 30 mins to 1 hr and after some time he become normal. we showed to many doctor all ECG, angiography, blood pressure, blood report everything comes normal. we are not sure what type of health issue is this. please help