First Virginia Banks agreed to sell its credit card portfolio to MBNA yesterday. Under terms of the agreement MBNA will acquire First Virginia’s $103 million portfolio with an expected closing date of Mar. 31. First Virginia expects to recognize a net after-tax gain of approximately $11 million. As part of the agreement, First Virginia will enter into an agent relationship with MBNA to continue offering credit cards under First Virginia’s existing brand names. According to CardData ([www.carddata.com]) First Virginia has approximately 200,000 gross accounts, 105,000 active accounts and 231,000 cards-in-force at the end of 1998.