The current Australian Open champions were expected to be strong challengers despite only reaching the Third Round 12 months ago, but it was clear they were in for a tough opener when they were forced to save break point as early as the third game of the match.
But neither duo could force a break of serve in the first set, setting up a tiebreak in which Heliovaara and Patten came into their own, breaking twice to go 4-0 ahead. Though Frantzen and Haase broke twice, the Finn and Brit had done enough for a 7-5 win in the tiebreak and 7-6 in the set.
The second set was equally as close as the first, with both pairs needing to save just one break point each as they headed rapidly towards 6-6 and another tiebreak.
As in the first set, the tiebreak was much more frenetic than the regular games, as both pairs dropped three points each before Heliovaara and Patten went 6-5 up to set up match point. On their own serve, the German and Dutchman defended well and went 7-6 ahead.
That gave them set point, but the former Wimbledon champions took the next two points to give themselves a second match point, but again they failed to break at the most crucial time.
It looked to be all over for Frantzen and Haase when a loss of serve put their opponents 9-8 ahead and serving for the match, but not only did they deny them again, they won three points in succession to take the set and stay in the match by the skin of their teeth.
Heliovaara and Patten did not seem to be rocked by that as the first 10 games of the third set all went with serve, but when serving in game 11, everything fell apart for the men from Helsinki and Essex, as they lost serve without taking a point.
That one game was in stark contrast to every one that had come before, but Frantzen and Haase did not care - they required three match points of their own in the next game, but they got over the line to win 7-5, completing an upset with a 6-7, 7-6, 7-5 victory.
Heliovaara's compatriot Emil Ruusuvuori has followed his First Round exit in the men's singles by doing the same in the men's doubles, as he and his French partner Adrian Mannarino were beaten in three sets by Orlando Luz of Brazil and France's Albano Olivetti (5-7, 7-5, 6-2).
Taking the inaugural set on the very first break point of the match put Ruusuvuori and Mannarino in the driving seat as the Finn continued his return to tennis following a long layoff due to injuries and mental health issues.
The pair survived two break points early in the second set, but their resistance was broken in the 11th game as Luz and Olivetti took break point before wrapping up the set in the next game.
That seemed to give the Brazilian and Frenchman real belief, as they broke serve on Ruusuvuori and Mannarino's first two service games in the final set, which allowed them to race into a 4-0 lead. With a fightback failing to materialise, they took the set 6-2 to win the match.