Answer: There is a sole opinion of the Maharsham, (Section B, 110:111,) that states that someone who abandoned his faith is invalidated for marriage. In order to take this Halachic opinion into consideration, the person should be advised to return and sanctify his wife (have a Halachic wedding ceremony,) in front of two witnesses. If he can carry this out without relating all the events that let up to it, for example if he tells her that in order to get a new ketuba (marriage contract) written, they must perform the ceremony again, this is a good idea. If he has no choice though, he should tell her. However, all of the above is a hiddur – a strengthening or beautification of the Mitzva, because the basic Halocho does not require it at all.