Wimbledon champions and French Open finalists Heliovaara and Patten were playing in the last four in New York for the first time, and a two-hour 20-minute quarter-final a matter of hours earlier was not the best preparation to face the fifth seeds, who were yet to drop a set all tournament.
So it appeared to be proving early in the first set, when Harrison and Skupski broke serve in the third game, but after holding off two more break point chances in the fifth, the top seeds broke back to level at 4-4, which eventually sent the set to a tiebreak.
However, two losses of serve did the damage for the Finnish-British pair, as the American-British duo took the tiebreak 7-4 for a 7-6 first-set win.
That tiebreak loss seemed to break Heliovaara and Patten's resistance, as they dropped another game early in the fourth set to find themselves 4-1 down, and despite saving two match points in game eight, Harrison and Skupski broke through at the third time of asking to wrap up a 6-2 win and end the match in one hour and 23 minutes.
"It wasn't exactly the best day for us," said Heliovaara after the match. "All credit to our opponents, they played really well. It's just that at this level, sometimes someone can beat us and others can play too."
The US Open remains the only Grand Slam where the Finn and Brit have never made the final, and at this year's, Harrison and Skupski will take on the German sixth seeds. All four players have reached the final at Flushing Meadows before, but none have ever won the trophy before.