How is it that babies who are stunted have more heart problems later? Isnt being thin good?

Makes no sense. Stunted? You mean short? Shorter children do not grow up to have more heart problems than taller ones; heart disease relates to individual risk factors like family history and lifestyle. As a general rule, it's better to be thin than to be obese; but children need enough calories to grow properly.
I think it's reverse. Kids with heart trouble have trouble gaining weight.

Related Questions

I was born in 1992 with infant alcahol synddrome. Did they have the technology back then to know if I had heart problems? My heart usually skips beats when I lay on myleft side or just sitting down. When I stand up my heart races

Palpitations. If you are having palpitations, you may want to see your family physician to see if there is a heart problem. This can be diagnosed with an ekg.
No known linkage. Fetal alcohol syndrome was first described in the 1960's among offspring of alcoholic mothers, many of whom died from their affliction within a year. The full spectrum of heart related effects included a transient heart murmur & holes between the lower or upper chambers. This was due to interference with heart development. Heartbeat issues are not part of the FAS description.

Feeling weak in legs? Doc says good blood flow, no heart problems, no anemia. 19, female, very slim/thin build.

Anything different. Are you walking more, going up hills wearing different shoes or on your feel all day? Take a look at what, if anything, is different in your life or activity right now. It may give you so, e clues since your tests were all negative.