Ventspils started pulling away at the end of the opening period, but it was a 10-0 run midway through the second quarter that gave the Latvians a game-high 13-point lead at 35-22.
Lietkabelis cut the gap to eight points (39-31) by the halftime break and scored eight points in a row to start the third quarter, tying the game at 39-all.
The guests from Ventspils regained a slight advantage in the fourth quarter and led 65-61 with 12 seconds left on the clock.
However, in the time remaining, Mantas Kazonas and Darrick Leonard buried a three-pointer each, while Sandis Valters went one-of-two from the free-throw line in between, as Lietkabelis ended up winning by a single point.
Kazonas led the Lithuanian side with 17 points, Leonard scored 13, while Ivan Nelyubov scored 12 points and grabbed eight rebounds.
The only Ventspils player in double figures was Ronalds Zakis with 16 points and five boards, as Harvey Grant and Maris Gulbis added nine points apiece.