LOS ANGELES - A top American Idol contestant was rushed to a hospital emergency room after Tuesday night's show suffering from heart palpitations and high blood pressure, a source close to the show said on Wednesday.

David Cook, who performed country legend Dolly Parton's ballad Little Sparrow on Tuesday's broadcast as one of the nine Idol finalists, was driven to a local hospital on the recommendation of a staff medic, the source said.

Cook, a rocker who sports a 'soul patch' on his chin and has been pegged by the judges as a possible dark horse to win the massively popular Fox television talent competition this year, was treated at the hospital and released.

The source said Cook, 25, had already returned to the set of Idol, which will eliminate another would-be star during the live Wednesday night broadcast.

No further details were available on Cook's condition, but the celebrity news website TMZ.com reported that he had been under stress in recent weeks due to an illness in his family.

People magazine reported on its website that Cook, who won praise from the judges by reworking pop hits such as Michael Jackson's Billie Jean into slow-burning rock songs, was noticeably absent from a gathering of fellow contestants just after Tuesday's broadcast.

Other finalists include: Brooke White, 24; early fan favourite David Archuleta, 17; Kristy Lee Cook, 24; Michael Johns, 29; and Ramiele Malubay, 20.

The winner of the show's seventh season will be announced during a live finale in May.