Sen. Bernie Sanders, I-Vt., a 2020 candidate, was hospitalized Tuesday in Las Vegas and underwent a significant medical procedure after a blockage was found in one of his arteries, his campaign said Wednesday.

Sanders, who is 78, has canceled all of his campaign events "until further notice."

"During a campaign event yesterday evening, Sen. Sanders experienced some chest discomfort. Following medical evaluation and testing he was found to have a blockage in one artery and two stents were successfully inserted," Jeff Weaver, a senior adviser to the Sanders campaign, said in a statement."

"Sen. Sanders is conversing and in good spirits. He will be resting up over the next few days. We are canceling his events and appearances until further notice, and we will continue to provide appropriate updates," Weaver added.

Later Wednesday, Sanders tweeted that he was "feeling good" and used the situation to tout his "Medicare for All" health care proposal.

Sanders had been in Las Vegas for a candidates' forum on gun safety co-hosted by MSNBC. Sanders will no longer participate in the forum, the campaign said.

Wednesday morning, the Sanders campaign canceled $1.3 million in television ad buys in Iowa, according to ad-tracking firm Advertising Analytics LLC. The campaign, following a massive fundraising quarter, had revealed the big buy just a day earlier. The first ad had been scheduled to begin running Thursday morning.

A Sanders campaign spokesperson told NBC News the ads will not air as planned, calling the development a “just a postponement.”

The news regarding Sanders' health comes just weeks after he had canceled three campaign events in South Carolina so he could rest his hoarse voice.

Aides to Sanders said at that time he was not feeling ill. Sanders also told NBC News at that time he would release medical records before the Democratic primaries get underway.

But Sanders' age (he turned 78 last month) has been a frequent issue on the campaign trail — although his two most prominent competitors, fellow septuagenarians Joe Biden (76) and Sen. Elizabeth Warren (70), also face similar questions. If elected president, Sanders would be the oldest commander-in-chief to ever be elected.

Nonetheless, his campaign announced Tuesday that it had raised a whopping $25.3 million during the past three months — an increase of more than $7 million from his second-quarter haul and more than any of the other Democratic presidential candidates who have so far released their fundraising numbers for the latest quarter.

But Sanders has dropped in polls in recent weeks. He trailed both Biden and Warren, D-Mass., in six of the last eight polls used by the Democratic National Committee to determine debate qualification.

Several of Sanders' competitors for the Democratic nomination wished him well.

Warren tweeted that she was wishing him a "speedy recovery," while Sen. Kamala Harris, D-Calif., called him a "fighter."

Sanders' procedure is a common one, with more than a million performed each year in the U.S.

It's not unusual for people in their 70s and 80s to have a stent — a tiny wire mesh tube that’s used to prop open a clogged artery so blood can flow more freely to the heart — placed, according to cardiologists. Age is one of the biggest risk factors for heart disease.

"People are generally out of bed and moving around within a day or two,” said Dr. Daniel Munoz, director of the cardiac intensive care unit at Vanderbilt University Medical Center. Munoz was not involved in treating Sanders.

"We tell people to take it easy for about a week before returning to a full schedule," Munoz told NBC News. But, he added, each patient is different, and some require longer recovery periods.