Nicklas Backstrom scored in double overtime to seal the victory after Troy Brouwer put the Capitals ahead in the second period only for Benoit Pouliot to level in the third.

Backstrom, who missed three months of the season with concussion, then scored 2:56 into the second overtime period to steal the win for Washington.

The East's top seeds, the New York Rangers, also suffered a setback as Chris Neil's overtime goal gave the Ottawa Senators a 3-2 victory which levelled their series.

The Rangers twice took the lead, through Anton Stralman and Brian Boyle, but twice the Senators fought back thanks to goals from Erik Karlsson and Nick Foligno.

Neil then scored 1:17 into overtime to hand Ottawa a much-needed win.

Goals in each period from Vladimir Sobotka, David Backes and Andy McDonald saw the St Louis Blues level their series against the San Jose Sharks with a 3-0 win.

Patrick Sharp scored with less than six seconds left in regulation, then Bryan Bickell scored his second of the game in overtime to give the Chicago Blackhawks a dramatic 4-3 win over the Phoenix Coyotes which left them tied at 1-1.