While getting a pair of 20-point games was an offensive boost for the ninth-seeded Shockers, it was their stingy defense that pushed them into the next round.
Wichita State held eighth-seeded Pittsburgh scoreless for nearly six minutes spanning the end of the first half and the beginning of the second half.
The Shockers went on an 11-0 run in that period and then sealed the win with a dominating 15-5 surge, which included a Tekele Cotton steal and slam and five points from Armstead.
Pittsburgh didn't look like a team that led the Big East in field goal percentage. The Panthers shot 35.2 percent from the field and hit only 1 of 17 3-pointers.
Pittsburgh guard Tray Woodall fouled out with 4:05 remaining, but the usually reliable senior guard didn't have much of an impact in this game. He went 1-for-12 from the field, missing all five 3-point attempts, and finished with just two points.
Freshman center Steven Adams topped Pittsburgh (24-9) with 13 points and 11 rebounds, but he was the lone bright spot for a Panther team that missed out on NCAA action last spring after 11 straight appearances.
Adams put Pittsburgh ahead 21-19 in the first half on a dunk, when Wichita State took over for good.
Early and Chadrack Lufile scored consecutive baskets on the inside to begin a half-ending 7-0 run that helped the Shockers take a 26-21 lead at the break.
Early began the second half with another inside hoop and Armstead hit a pair of free throws at the 18:46 mark to cap Wichita State's 11-0 run.
Adams' putback basket temporarily snapped Pittsburgh's cold spell, and Durand Johnson hit a 3-pointer to bring the Panthers to within 30-26. Pittsburgh had missed its first 10 treys before that long shot.
Carl Hall (11 points, six rebounds) got Wichita State back in the groove with a big dunk right after that, and the rout was on.
The Shockers (27-8) will take No. 1 Gonzaga.
NOTES: In an interesting coincidence, both teams had a starter from Nigeria. Pittsburgh's Talib Zanna is from the city of Kaduna, while Wichita State's Ehimen Orukpe hails from Lagos. ... Pittsburgh's Lamar Patterson was called for a Flagrant-1 foul for hitting Shockers' Ron Baker in the head with an elbow while driving. ... Shocker forward Carl Hall turns 24 on March 29. He is older than five NBA players from the Utah Jazz, who play at EnergySolutions Arena.