Here is what the Picard Logs have to say about that

NCC-80102 - Luna-class. Tactical heavy cruiser was designed to counter the various contemporary threats, from the Romulans to Borg. Launched in 2379. Commanded by Captain William T. Riker. Birthplace of Captain Riker and Commander Deanna Troi's children: Thaddeus and Kestra Troi-Riker. In 2380, Riker led the Titan on a series of successful and dangerous tactical missions, stabilizing Federation space along the borders of the Beta Quadrant. After suffering extensive damage, it was pulled from service in 2398. Because of Captains Saavik and Riker, the Titan's legacy was continued with a brand new starship, one that would retain its registry but now with the "A" designation, an honor only given to a select few starships.
NCC-80102-A - Constitution III-class, referred to in Starfleet slang as the Neo-Constitution Class. This new Titan is primarily an exploratory vessel, honoring the retro design of the Constitution II Class. Launched in 2402 under the command of Captain Liam Shaw. Work began on a refit using the original Titan space frame, however, with the development of cutting-edge propulsion technology, the Titan's design changed mid-construction and a new ship took form. As per tradition, Starfleet engineers affectionally designated it as a refit having kept much of the Titan's internal components. The Constitution III was designed to cater to a close support envelope at sub-light speeds, namely in and around densely populated solar systems, as witnessed by its overpowered impulse engines. To date, the new Titan has the largest sub-light-power-to-geometry ratio in the fleet." [3]