The first threat by the Baggies came from Salomón Rondón who tried to beat Adrián with a cheeky chip but his attempt went above the cross bar.
McClean tested Adrian moments later at the other end with a dipping strike, but there was nothing the Brazilian could do to prevent the Irishman from breaking the deadlock on 30 minutes after his shot deflected off Pedro Obiang and looped in just under the crossbar. They found it harder to stop the attacks and Manuel Lanzini slid a pass through to Arnautovic who should have won the game.
After trailing to a James McClean goal, the Hammers bounced back with a majestic header from the 1.93m Carroll, whose leap left West Brom defenders Jonny Evans and Kieran Gibbs grounded.
West Ham United are set to damage the survival hopes of another relegation rival with a bid for Joe Allen, reports Sky Sports. Aaron Cresswell fired in a cross and Andy Carroll rose highest to head past Ben Foster.
But West Brom hasn't won a game since their 3-1 loss against the newly promoted team Brighton and Hove Albion in the fourth fixture.
He's a former West Ham player of the year but fans - who once warmed to the Kiwi - turned on him on social media and in fans' forum with some suggesting he lacks pace, is too easily turned and has been "abysmal all season".
Seven of Albion's tired starters against the Gunners kept their places, with Jake Livermore a late replacement for Matty Phillips who felt his hamstring during the warm-up.
It was the Irish midfielder's first goal of the season, and in fact the first he had scored since a 4-2 win over the same opposition in September 2016. "And you have to give him great credit for the finish for the second goal as well". The entire bottom half of the Premier League could all go down as there are only a few points separating all the teams.
"And actually if we got through to the next round our next two games are on the Tuesday against Crystal Palace and Brighton on the Saturday after the fourth round".
"Do you not think the position you are in now the focus would only be on your Premier League status?"