Dec. 31, 2009— -- Rush Limbaugh is undergoing a battery of tests today as doctors try to determine the source of the chest pains that sent the popular talk-radio host to the hospital overnight while on vacation in Hawaii.
Limbaugh "continues to rest comfortably in a hospital in Honolulu," guest announcer Walter E. Williams said on Limbaugh's radio program today. "He had a comfortable night and he is getting good medical attention."
During his opening monologue, Williams said Limbaugh was undergoing a multitude of tests today.
"Those pains were the kind of pains that make one feel like he has a heart attack coming on but it has not been confirmed that is a heart attack," he said. "Today, Thursday, he will have a complete examination and we will know more."
Limbaugh had been scheduled to return to his talk show Jan. 4 but a spokesman told ABC News that it is unclear whether he will be back by then.
"Rush is in good and stable condition … comfortable -- as comfortable as can be in a hospital on vacation," Williams said. "And he is in good hands."
According to a statement from "The Rush Limbaugh Program," "Rush appreciates your prayers and well wishes, and he will keep you updated via RushLimbaugh.com."
Sources say Limbaugh told emergency workers he was taking medication for a back problem. He was treated at the hotel before being transferred to the hospital.
While in Hawaii on vacation over the holidays, Limbaugh had been seen golfing at the Waialae Country Club, according to KITV.
Limbaugh has been a polarizing figure in U.S. politics, once asking, "What is so wrong with saying I want Barack Obama to fail?"
But he made headlines in 2003 by admitted an addiction to painkillers after reports claimed he was illegally obtaining narcotics. He settled the charges against him in a plea deal that included a $30,000 fine. He entered a drug rehabilitation program.
Yet in recent years he has seemed to have a renewed commitment to healthy living, even announcing in the fall that he'd lost about 90 pounds since March.
Rush Limbaugh: Career of Controversy
The enormously popular conservative radio host has been expressing his political views three hours a day, five days a week for more than two decades.
With only rare appearances by guests or interviews, Limbaugh's program is a monologue, with occasional pre-screened callers. His brand of conservative talk radio has spawned many imitators, although none has reached his level of influence on political discourse.
He boasts an audience of about 14 million listeners and gets most of his headlines from his controversial statements.
Earlier this year, he generated controversy when he expressed interest in becoming a part-owner of the St. Louis Rams. The deal never came to fruition but several players came forward in October to say they would not take the field if Limbaugh won his bid.