Actually, St. Patrick, Enlightenter of Ireland, confessed the Nicaean Creed without the filioque, the innovation adoption of which by the Popes of Rome plunged the western patriarchate into heresy. In his day, 'catholic' and 'orthodox' would be used interchangably.
As the words are currently used in common usage, there is a better case to be made for St. Patrick being Orthodox.
Ah, the old filoque debate. To quote Scripture, which is something Catholics aren't known for doing, let's go to John 20: 22-23. "And when He [Jesus] had said this, He breathed on them and said to them, 'Receive the holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.'"
If the holy Spirit comes from God the Father, how can Jesus say this? It is through the doctrine of the Holy Trinity that Christians, and Trinitarians specifically, state that the Three Persons are One God. Since the Three are One, Jesus can do this, and therefore, Spirit can proceed from both the Father and the Son. Saying the Spirit proceeds from the Father is correct, but also saying that it proceeds from the Father and the Son is also correct.