Chapman was hospitalized Monday for what was described at the time as a heart emergency.
He spoke Wednesday with Denver station KDVR, saying his chest pain has lessened since the incident.
"It feels much better now. And I'm going through some psychological things right now too, so that doesn't help," Chapman said. "I think, basically, I had a broken heart. And of course, it's going to heal."
The reality star said his assistant took him to a hospital in Castle Rock for treatment Monday.
"I couldn't breathe. It was like I had ran a 3- or 4-mile run," Chapman said.
He said he's unsure exactly what caused the episode. But he has more tests scheduled Thursday and Friday.
"There's something haywire or it's psychologically. I don't know," Chapman said. "I guess things happen like that. I've never... I don't do drugs."
He said three of his children are in Colorado to accompany him during his recovery.
Chapman became known to television audiences via "Dog the Bounty Hunter," a reality TV series that aired from 2004-2012. His current series, "Dog's Most Wanted," airs on WGN America.
His late wife, Beth Chapman, starred alongside him on both his current and former series until her death in June after battling throat cancer.
They had been married since 2006 and raised 12 children together, some from previous relationships. Both Dog and Beth were born in Denver.
In August, an official Dog and Beth merchandise store in Edgewater was burglarized. The family said thousands of dollars in merchandise along with personal items were stolen and photos showed the damage.