A serious heart condition in one's youth (infancy, even), regardless of insurance coverage at the time, could exclude one from all future private insurance (as in: there are zero options, they will not do business with you) leaving only incredibly-expensive state-provided (but privately administered, of course—profit over all) insurance as an "option", i.e. leaving the only actual options as being employed with a large company, going without insurance at all, or being poor enough to qualify for medicaid (so, avoiding employment).

Source: I know someone for whom this was the case pre-ACA.