Chris Copland scored the winning lay-up with a second remaining, and Argentinean Luis Scola finished with team and season-highs 24 points and nine rebounds for Indiana who rested starters Paul George, George Hill, Lance Stephenson and David West.
Indiana improved their record to 54-25, moving a half-game ahead of the Heat, who lost 107-102 at Memphis Grizzlies.
Zach Randolph had a team-high 25 points and 11 rebounds, and Spaniard Marc Gasol added 20 points and 14 rebounds as the Grizzlies kept their play-off hopes alive.
LeBron James led the Heat with 37 points, but his five turnovers proved costly for the reigning champions, who will host Indiana on Friday
With the win, the Grizzlies trail the Phoenix Suns – who defeated the New Orleans Pelicans 94-88 – by a game for the final play-off spot in the Western Conference.
Meanwhile, the Cleveland Cavaliers routed the Detroit Pistons 122-100, but they were eliminated from play-off contention with three games left in the regular season.