Coroner Mike Murphy said an autopsy, toxicology and microscopic samples showed the 52-year-old Gans' death was not an issue of drug abuse.
Murphy said Gans had toxic levels of hydromorphone in his system when he died. The opiate drug is used to treat chronic pain, which Gans suffered from, Murphy said.
Gans had a toxic reaction to the drug because of an existing heart condition and a blood condition.
"Mr. Gans' health conditions placed him at greater risk for heart irregularities, and the hydromorphone was a factor in exacerbating those risks," Murphy said.
Murphy said Gans had hypertensive cardiovascular disease, a condition that causes increased blood pressure and makes the heart work overtime, which left him more susceptible to heart irregularities.
Gans also had a condition that caused his red blood cell count to go up, Murphy said. Polycythemia is the opposite of anemia.
Police say Gans was found dead in bed at home in Henderson early May 1 after his wife, Julie, reported she couldn't rouse him.
At his death, his manager Chip Lightman described Gans as an energetic health nut who watched his diet, loved to perform, and relished his involvement in Las Vegas-area fundraisers and philanthropic causes.
"I managed him 18 years and health was never an issue," Lightman told The Associated Press at the time. "Danny lived a good, clean Christian life. He was not a drug user. He would have a glass of wine because they say red wine is good for you. He didn't smoke."
Gans was a singer, actor and impressionist who spent more than a decade working his way to top billing on the Las Vegas Strip.
He was a one-time minor league baseball player who left a one-man Broadway show in the 1990s to spend more than a decade working his way to top billing at the Encore Theater at Wynn Las Vegas on the Las Vegas Strip.
His show brought impressions in rapid-fire succession — Tony Bennett, Al Pacino, Sarah Vaughan, Clint Eastwood, Rodney Dangerfield, Woody Allen, Bill Cosby, Kermit the Frog, Jimmy Stewart.
He was mourned when he died as a "great entertainer and Las Vegas icon," by Las Vegas entertainment legends Siegfried Fischbacher and Roy Horn. Donny and Marie Osmond paid tribute to Gans the day he died with a video of Gans performing songs from his act at the end of their show at the Flamingo Las Vegas. Gans was a co-producer of the Osmonds' show.
A May 21 memorial drew about 1,000 guests at the Encore Theater, including casino mogul Steve and Elaine Wynn. Steve Wynn made Gans a headliner when he owned The Mirage and hired him again to perform at the Encore, a sister property to the Wynn Las Vegas, beginning Feb. 10.