Heart surgery at 18 years old. will it rule me out for lots of good jobs?

Should not: Cardiac surgery if succesfull should not impact your ability to perform the majority of jobs out there.

And your outcome??: Heart surgery at 18 might mean something as benign as a trans-vascular ASD closure or a heart transplant. Your general health & lifestyle achieved after the procedure will set stage for what you can do. If you are playing racket ball 2 days a week & cycling 6 miles/day the types of work you compete for will be different than those you pursue if you must maintain a quiet lifestyle.