With the Reds trailing 4-3 in the seventh, Joey Votto and Jay Bruce singled off Tim Byrdak (2-1).
Josh Stinson came in to relieve and Heisey (3-for-5, two runs scored) greeted him with a homer into the left field stands, handing the Reds a win in the opener of a season-ending three-game series.
Lyle Ondrusek (5-5) earned the victory after recording the final out of the sixth and Francisco Cordero racked up his 35th save.
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