From this post: http://www.livejournal.com/talkpost.bml?journal=lesbian&itemid=1295032
Vagina Fact: The Secret of Hearts
The typical shape of a heart has been represented for years as a universal symbol of love. Yet the what we have come to recognize as a Heart was actually recognized in the days of the ancient Romans and the Greeks as the the representation of a vagina. The two upper curves of the heart symbol were the representation of the outer labia, while the sharpened bottom represented the inner labia.
The Heart symbol would often be found in the temples of Venus (Aphrodite) and Juno (Hera) the two major matriarchal goddesses. However the symbol was typically associated with Venus, not because she was the goddess of love, but that she was the goddess of sex and adour.
What one must keep in mind is that in opposition of what has been written about Greek life is the belief that they were a patriarchal favoring society. This is untrue in everyway. In fact, it is just the opposite. The Greecian society lived in honor and reverence of women, and saw them each as goddesses in their own way. And they had variety of depictions of how their goddesses looked on terms of physical beauty. Archeology has discovered from painted statues that Aphrodite was not blonde but rather she was red. Athena the Goddess of Wisdom had raven features, and the goddesses Hera and Maia were blondes.
What is also proof of Greek matriarchal favoring is that Greece was the first country in Europe if not the world where female homosexuality surfaced, from the island of Lesbos thus giving female homosexuals today the title of lesbians. Because of this understanding of female homosexuality they were like-wise open to male homosexuality, which flourished during the Alexandrian period of Greece.
Over time with the fall of matriarchal favoring Greece and the growing patriarchal Rome, along with the spread of Christianity, the vaginal symbol of Aphrodite was converted into the symbol that we know it as today, simply because of the fact that the patriarchal Christian religion could not tolerate a representation of female sexual pleasure. Especially when it was associated with female homosexuality.
Thus the true meaning of the heart symbol.