"The story on clean coronaries is a little more complicated, as some people can have ischemic heart disease -- decreased blood flow to the heart muscle -- even with no blockages in the arteries that are seen on the angiogram," he said.
Both the hospital and Limbaugh's camp had remained mum on his condition throughout the day on Friday, one day after a spate of statements and press releases said he was "resting comfortably" and undergoing a battery of tests.
Many fans called into his show today to wish Limbaugh well, according to The Associated Press. They were asked simply to say "ditto," a favorite Limbaugh phrase, to keep the show moving.
As of Thursday, doctors were still trying to determine the source chest pains that sent Limbaugh to the hospital while on vacation in Hawaii.
Walter E. Williams substituted for Limbaugh on Thursday and said Limbaugh went to the hospital because of chest pains.
"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," Williams said.
Cardiologists said that there are many other possible culprits for the chest pains that sent him to the hospital.
"There are ... dozens of other potential causes of chest pain, most of which are not life-threatening," Bhatt said. "Common masqueraders include musculoskeletal pains, acid reflux and other digestive disorders like ulcers, and stress."
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.
Paramedics arrived at the Kahala Hotel and Resort at 2:41 p.m. Wednesday and found Limbaugh, 58, sitting in a chair in his ninth-floor hotel room, according to ABC's Honolulu affiliate KITV.
Limbaugh told emergency workers he was taking medication for a back problem, sources said. However, at Friday's press conference Limbaugh denied that he had been taking the medications. He declined to answer further questions.
Limbaugh 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.
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.