Doctors confirmed on Friday that US Senator Bernie Sanders suffered a heart attack three days ago, as they announced that he had been released from the hospital in Las Vegas.

Sanders, 78, said he felt "great," according to a statement from his campaign for the 2020 Democratic presidential nomination.

"Sen. Sanders was diagnosed with a myocardial infarction," his doctors said in the statement, using the medical term for a heart attack.

"Two stents were placed in a blocked coronary artery in a timely fashion. All other arteries were normal.

"His hospital course was uneventful with good expected progress."

Sanders put his bid for the White House on hold after experiencing chest discomfort while on the stump in Las Vegas on Tuesday.

"After two and a half days in the hospital, I feel great, and after taking a short time off, I look forward to getting back to work," Sanders said.

The far-left senator from Vermont is expected to participate in the fourth Democratic debate scheduled for October 15 in Ohio.

Sanders is the oldest candidate vying to take on President Donald Trump, 73, and is third in the Democratic nominee polls behind Joe Biden, 76, and Elizabeth Warren, 70.

Sanders' health has generally been good and it has been Biden who has had to bat away questions about his stamina and mental sharpness. 

In March, Sanders gashed his head on a shower door and had seven stitches, but quickly returned to the campaign trail.

Last month, he canceled three events in South Carolina to rest his voice, which had become hoarse.

Sanders, a self-described Democratic socialist, wants to tax the rich more and introduce universal health care.

He pushed Hillary Clinton to the wire for the nomination in 2016.