American Idol contestant David Cook was taken to the hospital last night following his performance on the show, after he experienced heart palpitations, a source told People.com. He looked and sounded confident during his rendition of Dolly Parton’s “Little Sparrow” and smiled during the judge’s comments, though he’d been feeling ill earlier in the day. He was examined by the show’s medics, who urged him to go to the hospital immediately, but he was determined to wait until the show was off the air. He was escorted to the hospital, treated for high blood pressure and released several hours later. An “A.I.” exec told TMZ.com that Cook has been under a lot of stress because his brother, who has cancer, had a setback. Earlier in the season, just before a performance, David collapsed and said he could not go on — but pulled it together at the last minute and went on to perform.