The 39-year-old rapper cut short his song "Heartless" to announce the news to the crowd, reported People magazine.
West had gone on stage at 8:45 PM He was initially scheduled to perform until 10 PM, but ended his set at 9:40.
The singer performed "Father Stretch My Hands Pt. 1", "Famous" and an abbreviated set of his recent featured verses, including Drake's "Pop Style", ScHoolboy Q's "That Part", "Mercy", Chief Keef's "Don't Like" and his own "All Day".
"Wolves" was the last full song he got through, before his brief performance of "Heartless".
The emergency due to which he left is still not known.