Welcome to HCM,
You are relatively young and suffered a myocardial infraction and It was revascularized with by pass surgery so you should take care of your health.
I hope you must be taking your treatment regularly,and keeping good control of diabetes
,usually a Beta blocker
is given as secondary prevention if you are taking dose of drug can be increased in consultation with your treating Physician as light lightheartedness may be due to meneiere's or high blood pressure
> 140/100 it must be lowered to 130/80 mm of hg.
Reduce your salt intake to 2.5 gm/day if BP is not controlled with beta blocker some other anti hypertensive can be given.