The Swedish national team struggled to score in the Ice Hockey World Cup quarter-final against Finland, but Joel Eriksson Ek made it 2-1 in overtime.
Mats Zuccarello's Minnesota Wild teammate blocked a shot from Victor Hedman in Game 4 of three.
The host country, the Czech Republic, is also ready for the semi-finals after Pavel Zacha scored the only goal in the match against the United States.
Canada and Switzerland won earlier on Thursday and ensured that three of the four teams qualifying for the semi-finals belonged to the Norway group.
Finland performed poorly in the group stage and would have been eliminated before the cup if Austria had not lost to relegation-ready Great Britain in the final round.
Meanwhile, Trey Cronauer progressed through the second set with seven straight wins and a maximum of 21 points. But the outcome of the adjacent duel was not at all clear. Finland shut out again and held the game scoreless through the first two periods despite Sweden winning by shooting statistics of 13-5 and 11-3 respectively.
It was tied in the third game, but after 55.02 the opening came. Eero Pakarinen went for the trick, and was passed by Rasmus Dahlen. Then he shot between the legs of goalkeeper Emile Larme from an acute angle.
It looked like it would send Sweden to the semi-finals, but Finland set out at a desperate pace, and with 58 seconds left the ball was in Sweden's goal.
Extra time was scoreless until Helenius was sent off for pressing Adrian Kempe. In four to three, Sweden scored the winning goal.
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