Anathema isn’t quite the same thing. In the Torah, anathema initially meant something set aside for religious use as opposed to secular uses. Later on, it also took on the idea of something that was set aside to be cursed by God, and had a dual meaning. With wasn’t until the 4th century that we see anethema used as a formal excommunication.
The problem with using excommunication in the context of the Seven is that the Faith of the Seven doesn’t have communion as a concept, given that communion is really closely linked to the idea of the Eucharist. Now, that’s not to say that there aren’t other examples of such a ceremony in other religions – various Hellenic mystery cults included the idea of a death-and-rebirth diety whose body is ritually consumed to associate the worshipper with both sacrifice and divinity, most notably the worship of Dionysus who supposedly was dismembered by the Titans and then brought back to life.

The problem is that the Faith of the Seven doesn’t have a dying-and-rebirth figure either, and there really doesn’t seem to be any basis for a communion ritual in their liturgy.
My guess would be that “anathema” in the context of the Faith of the Seven has more to do with a religious denunciation for some great sin, similar to how the High Septon decreed that King Aenys was an abomination for marrying his son to his daughter.