On Tuesday night's "Late Show with David Letterman," Emmy-winning "Entourage" star Jeremy Piven opens up to Dave about the controversy surrounding his exit from the Broadway play Speed the Plow last year.

Last week an arbitrator ruled in Piven's favor after he was sued by the producers of David Mamet's Speed the Plow after he left the show citing mercury poisoning, "which sounds like a rich man's disease," Piven tells Dave, "sounds like something you might get from the leather seats in your Lamborghini, like a rash, like a rash that hurts."

Piven says the doctors who tested him said, "'You've got elevated levels of mercury we've never seen before, basically almost a 60. We should not have anything above a 3.'" He added that he "also had Epstein-Barr, which is, you know, mono. … There were so many different variables that were contributing to my situation."

But "Entourage"'s Ari Gold finds the humorous side of the situation when Dave asks him how he got both mercury poisoning and Epstein-Barr: "Just from being a coward," Piven jokes.

Piven says he "brought the test results to the company, to the Speed the Plow people and I told them what was going on with me. They knew what was happening," he says, adding a doctor helped him through the production. But he says his health took a turn for the worse and resulted in a three-day stay at the hospital, where doctors told him he could suffer a heart attack if returned to the show.

He continues, "at a certain point, you're brought to your knees and you realize, 'I gotta find balance.' It happened to me, I'm so sorry that it happened because I wanted to continue the [Broadway] run. It was the time of my life."

For the whole interview, plus actress Rumer Willis and musical guests The Black Crowes, tune in to Tuesday night's "Late Show" at 11:35 p.m. on CBS.