WASHINGTON (AP) — Bernie Sanders’ campaign said Wednesday that the Democratic presidential candidate had a heart procedure for a blocked artery and was canceling events and appearances “until further notice.”

The 78-year-old Sanders was in Las Vegas when, according to a campaign statement, he experienced chest discomfort during a campaign event Tuesday and sought medical evaluation. Two stents were “successfully inserted” and that Sanders “is conversing and in good spirits,” according to the campaign.

Sanders’ wife, Jane O’Meara Sanders, was en route to Las Vegas on Wednesday and said in an email to The Associated Press that her husband was “doing really well.”

Tick Segerblom, a Clark County, Nevada, commissioner who was at Sanders’ fundraiser Tuesday said Sanders seemed fine at the time. “He spoke well. He jumped up on the stage. There was just nothing visible,” Segerblom said.

The Democratic field’s oldest candidate, Sanders sometimes jokingly refers to his age at town halls and other events, especially when interacting with younger participants. His aides have tried to project him as a candidate with energy levels that surpassed his 2016 presidential campaign.

He is one of three candidates over age 70 in the Democratic primary, which has spurred debate over whether the party should rally behind a new generation of political leaders, and President Donald Trump is 73. Sanders’ health issue is certain to revive that discussion in the weeks before the next presidential debate this month.

Sanders’ campaign manager, Faiz Shakir, was on a telephone call with supporters Tuesday night but didn’t mention any health concerns about the candidate. Shakir said the “state of the campaign is strong” and he played up Sanders’ strong fundraising total for the third quarter. The Vermont Senator’s campaign raised $25 million, the highest among the candidates who have reported so far, and scheduled its first television ads in Iowa. On Wednesday, it suspended those spots, too.

Sanders had been among 10 Democratic candidates scheduled to appear later Wednesday at a forum on gun control in Las Vegas. He recently canceled some appearances in South Carolina because he lost his voice. The campaign said at the time he felt fine.

During the first debate in June, Sanders heatedly defended his 76-year-old rival, Joe Biden, after California Rep. Eric Swalwell, 38, said it was time to step aside for a new generation. Sanders told reporters later the question smacked of “ageism.”

“The issue is, who has the guts to take on Wall Street, to take on the fossil fuel industry, to take on the big money interests who have unbelievable influence over the economic and political life of this country?” Sanders said on the stage that night.

The health issue comes as Sanders’ campaign has been trying to turn a corner after a summer that saw him eclipsed as the leading liberal in the field by Massachusetts Sen. Elizabeth Warren, 70. Sander has dropped well behind Warren and Biden in most polls and recently reshuffled his staffing in early states to become more competitive.

“Given his recent stalls in the polls, the timing is pretty bad here,” Democratic strategist Jim Manley said of Sanders’ heart procedure.

Sanders’ rivals were quick to wish him well. “We want to send our best wishes for a quick recovery to @BernieSanders today,” tweeted Julian Castro, an Obama administration housing chief. Added Sen. Kamala Harris of California: “If there’s one thing I know about him, he’s a fighter and I look forward to seeing him on the campaign trail soon.”

Sanders mounted an insurgent campaign against Hillary Clinton for the party’s nomination in 2016. He is a top contender in the 2020 primary, and announced Tuesday that he raised more than $25 million over the past three months. But he is facing stiff competition from former Vice President Joe Biden and Massachusetts Sen. Elizabeth Warren, who have overtaken him in many polls.

Sanders is not the first candidate to face health issues in recent years while seeking the presidency. Clinton had to take time off from campaigning in 2016 after being treated for pneumonia.

In 2000, former New Jersey Sen. Bill Bradley, the leading Democratic challenger to then-Vice President Al Gore, had to cut short a campaign swing for treatment of an atrial fibrillation, an irregular heartbeat that is treatable but potentially serious. Bradley later resumed his campaign.

In Sanders’ case, when doctors insert a stent, they first thread a tiny balloon inside a blocked artery to widen it. The stent is a small wire mesh tube that then is propped inside to keep the artery open. The number of stents needed depends on the size of the clog.

The treatment can immediately improve symptoms such as chest pain or shortness of breath. The stents are threaded into place through blood vessels in the groin or wrist, requiring only a tiny incision. Most are coated with medication to prevent the targeted artery from reclosing. That is still a risk, requiring monitoring, and patients also often are prescribed blood thinners to prevent clots from forming in the stents.

A letter released by Sanders’ physician in 2016 cited a history of mildly elevated cholesterol but no heart disease.