It's just a muscle. It may be leaner since it works a lot, but it's all gonna get broken down into amino acids and then built up to make protein. Just like other bits of the chicken, Nothing special.
Actually Tar Baby, that's not true. The heart of the chicken has an extra amino acid that acts like a super amino.
Not as bad as other chicken organ meat like livers and gizzards. Both of them are fairly high in cholesterol. Three ounces of chicken livers contain 536mg of cholesterol, same amount of gizzards contain 165mg and a single chicken heart contains only 8mg. of cholesterol. I've eaten my share of chicken organ meat and the hearts are not bad, just a bit chewy since it is a muscle.
Love em. No idea about the nutritional value though. Don't mind chicken livers as well, but prefer hearts.