a. The provisions of this article shall not apply to any cause of action which arose prior to July 1, 1976, and as to which the statute of limitations had not run prior to that date, regardless of the date any suit brought thereon is filed. Notwithstanding the foregoing, in actions which accrued prior to July 1, 1976, if a claimant has filed notice under § 8.01-581.2 of this article, his cause of action and any defense thereto shall be governed by this article.
b. The term “has filed,” as used in this section, is deemed to include the filing of notice under § 8.01-581.2 (or under repealed § 8-912) of this article where such filing occurred prior to the expiration of any applicable statute of limitation when the cause of action arose prior to July 1, 1976. This subsection (b) shall be applied retroactively to such causes of action.