Declarer can guard against a 4-1 split with North holding four hearts including the ♥J, provided Dummy's ♥Q is not played on the first or 2nd trick.
The ♥Q must be kept in Dummy (combined with the ♥10) for a possible finesse against North's ♥J !

If, on the other hand, South holds four hearts including ♥J, Declarer will always lose one heart trick and there is nothing he can do to prevent it.