Clark County Coroner Mike Murphy said an autopsy, toxicology and microscopic samples showed the 52-year-old Gans died from toxic levels of hydromorphone. The opiate drug is used to treat chronic pain, which Gans suffered from, Murphy said.
Murphy said Gans had heart disease caused by high blood pressure _ which makes the heart work overtime and left him more susceptible to heart irregularities. Gans also had a condition (polycythemia) that results in too many red blood cells, Murphy said.
"Mr. Gans' health conditions placed him at greater risk for heart irregularities, and the hydromorphone was a factor in exacerbating those risks," Murphy said.
Gans was found dead in bed at home in Henderson early May 1 after his wife, Julie, reported she couldn't rouse him.
Upon Gans' death, his manager Chip Lightman described Gans as someone 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."
On Tuesday, Lightman said: "Everyone knew he had two shoulder surgeries and excruciating back problems."
He attributed Gans' pain to injuries dating back to his years playing baseball.
A one-time minor league baseball player, Gans was a singer-actor-impressionist who spent 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.
A May 21 memorial drew about 1,000 guests at the Encore.