The Heat opened up a 20-point lead after three quarters and there was no way back for the Spurs who were led by Tim Duncan's 23 points.
Carmelo Anthony followed up his 62-point night on Friday with another 35 on Sunday as the New York Knicks beat the Los Angeles Lakers 110-103.
Raymond Felton also added 20 points for the Manhattan outfit with Jodie Meeks top-scoring for the Lakers with 24.
The Cleveland Cavaliers scored just six points in the third quarter as they went down to a 99-90 defeat to the Phoenix Suns.
The Cavs had held a 61-43 lead at half time but that was wiped out as the Suns pulled away for victory.
The struggling New Orleans Pelicans made it back to back wins as Tyreke Evans scored 23 points in a 100-92 win over the Orlando Magic.
Orlando swingman Arron Afflalo was the game's top scorer with 25 points.
The Brooklyn Nets eased to a fifth-consecutive win as they beat the Boston Celtics 85-79.
Kevin Garnett and Paul Pierce scored just six points apiece on their first return to Massachusetts since being traded by the Celtics in the summer.
The Portland Trail Blazers slipped two games behind the Oklahoma City Thunder in the Northwest Division as they lost 103-88 to the Golden State Warriors.
Stephen Curry recorded 38 points, eight assists and seven rebounds for the Warriors who trail the Los Angeles Clippers by 3.5 games in the Pacific Division.
In the day's other games, the Denver Nuggets beat the Sacramento Kings 125-117 while the Dallas Mavericks were 116-106 victors over the Detroit Pistons.