Lady Gaga performed before fans on Oprah Winfrey's show just hours after she was declared unfit for a gig.
The "Poker Face" singer was slated to croon at Purdue University in Indiana on Thursday night but the performance had to be cancelled at the last minute after paramedics found Gaga had an irregular heartbeat.
She later apologised to fans through her Twitter page.
"I''ve been crying for hours, I feel like I let my fans down 2nite. An hour before the show, I was feeling dizzy and having trouble breathing," the Daily Star quoted her as stating on Twitter.
She added: "Paramedics came to take care of me, and told me my heart-rate was irregular - a result of exhaustion and dehydration. I can''t apologise enough for how sorry I am. I could hear my fans cheering from my dressing room, I begged everyone to let me go onstage."
And soon she was in Chicago singing live on Winfrey''s show.
Dressed in a spiked black outfit she gave her usual power packed performance.