Senator Bernie Sanders had a heart attack this week, his presidential campaign said on Friday as he left a Las Vegas hospital, following three days of near-silence from the candidate and his advisers about his health.
Mr. Sanders, 78, had entered the hospital on Tuesday night after experiencing chest pain at a campaign event, and doctors had inserted two stents in a blocked artery, a relatively common procedure. But the campaign did not confirm he had had a heart attack until Friday, leaving open questions about Mr. Sanders’s condition as he remained off the campaign trail this week.
Television cameras filmed Mr. Sanders as he left the hospital Friday, waving to onlookers and pumping a fist, then driving off in a sport utility vehicle. He will remain in Las Vegas on Friday night and return to his home in Burlington, Vt., on Saturday, campaign officials said.
“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,” Mr. Sanders said in a statement.
While much of the conversation in the Democratic race has centered on issues like health care and student debt, Mr. Sanders’s heart attack is likely to heighten scrutiny on age in a primary where the top candidates are all in their 70s. In addition to Mr. Sanders, former Vice President Joseph R. Biden Jr. is 76 and Senator Elizabeth Warren is 70. President Trump is 73.
But if Mr. Sanders has until this week largely avoided questions about his health — he has projected an image of fitness as a candidate and has maintained a blistering schedule on the campaign trail — the spotlight is now squarely on him. The ages of the current leaders notwithstanding, many Democratic voters have expressed discomfort with nominating a septuagenarian candidate, a notion that some political strategists say Mr. Sanders’s heart attack is unlikely to dispel.
“Running for president is a physical and emotional trial, and the presidency itself is even more demanding,” said David Axelrod, a former top adviser to President Barack Obama. “While we all wish Senator Sanders well, this has to be a big flashing light for him. And given his age, it may be for some voters, as well.”
Mr. Sanders began experiencing chest discomfort on Tuesday evening during a grass-roots fund-raiser he was hosting at a Las Vegas restaurant. As he began taking questions from the audience, he asked a campaign aide for a chair. He did not stay much longer at the event, and became visibly uncomfortable in a car afterward, according to two campaign officials, who spoke on the condition of anonymity to discuss a sensitive topic.
At that point, Mr. Sanders was taken to an urgent care facility, where doctors determined he should be transferred to a hospital. He was then taken by ambulance to Desert Springs Hospital Medical Center.
At the hospital, he was taken immediately to the cardiac catheterization laboratory, where doctors inserted two stents into a blocked artery. By Wednesday, he was talking to his campaign manager, Faiz Shakir, about the campaign. By Thursday, he was walking laps around the hospital hallway, the officials said.
His doctors in Las Vegas, Arturo E. Marchand Jr. and Arjun Gururaj, said in a statement that Mr. Sanders’s “hospital course was uneventful with good expected progress.” He spent three nights at the hospital.
Mr. Sanders canceled his events and appearances for the week, though his campaign has said he will participate in the next Democratic debate, to be held near Columbus, Ohio, on Oct. 15.
A heart attack means that a portion of the heart muscle died, starved of blood when a vessel was blocked, said Dr. Gilbert Tang, a heart surgeon at Mount Sinai Hospital in New York.
“The first question is, how serious was the heart attack? What muscle was damaged and how will that affect the heart’s function?” Dr. Tang said. “If it was a significant portion of the heart, will that affect the heart’s ability to pump?”
If only a small portion of heart muscle was damaged, he said, Mr. Sanders should make a full recovery — even at 78. These days recovery does not depend on age so much as other medical issues, like lung problems, he said.
That does not mean that Mr. Sanders can simply continue as if nothing happened, though. Doctors usually recommend a cardiac rehabilitation program, which is essentially an exercise program in which patients are closely monitored. Such a program, Dr. Tang said, “conditions the heart to work harder.”
Mr. Sanders will also most likely take a cocktail of drugs to reduce his risk of another heart attack, including powerful anti-clotting drugs that require close monitoring for a month.
In the 2016 presidential campaign, Mr. Sanders’s doctor said that the senator was “in overall very good health.” His ailments included gout; a mild elevation of cholesterol; an inflammation of out-pouches in the bowel known as diverticulitis; and hormone replacement therapy for an underactive thyroid gland. He had no reported history of heart disease.
Among the other candidates, Mr. Biden underwent emergency surgery in 1988 for a near-fatal ruptured berry aneurysm of an artery in his brain. He also underwent surgery to remove a second berry aneurysm. In 2008, Mr. Biden’s doctor said that he had recovered fully.
Mr. Trump has not had a medical emergency while running for or serving in office, though he has not released as much medical information to the public as other recent presidents have. This year, the White House physician pronounced Mr. Trump in “very good health,” although the president had gained weight and is now officially obese.
Before his heart attack pulled him from the campaign trail, Mr. Sanders was polling in the top tier of the Democratic primary race with Mr. Biden and Ms. Warren, and his staff has been trying to project optimism about his candidacy. But the episode has cast a shadow over his campaign just as he was attempting to reinvigorate it after a summer slump that saw his standing in some polls slip.
Hoping to reverse course, he had recently begun to focus more on his electability, arguing that he is the candidate best positioned to beat President Trump in the general election.
The Sanders campaign announced this week that it had raised $25.3 million in the third quarter, placing him ahead of Ms. Warren, his chief ideological rival, by a hair and at the top of the field in fund-raising.
In a show of force, the campaign announced a $1.3 million ad buy in Iowa that it then postponed as it waited to assess the situation; the ad will now begin airing next Tuesday, and will run for two weeks as planned.
Campaign officials said they would determine when he would return to the trail as he recovers at his home, and it is possible that his first public appearance will be at the debate. His demeanor then will likely be watched closely by both voters and the news media.
Already, Mr. Sanders is working against a built-in bias. When asked about age, voters show a clear preference for younger presidential candidates, with an overwhelming majority saying they prefer candidates in their 40s through 60s, according to surveys. When asked about the ideal age for a president, just 3 percent said the 70s, according to polling released by Pew Research Center in May. Other polls have shown that Americans express more discomfort with a candidate in his or her 70s than one who is gay, Muslim or an independent.
Bryce Smith, 27, the Democratic Party chair in Dallas County, Iowa, said Mr. Sanders’s health scare could hurt his chances — particularly against Ms. Warren.
“I do see that as something that is going to deter people that were maybe on the fence,” he said. “If anyone was teetering between Elizabeth Warren and Bernie Sanders, this probably showed them that Elizabeth Warren has the stamina and the health and little bit younger age to see it through eight years.”
Jill Alper, a Democratic strategist in Michigan and a veteran of Bill Clinton’s and John Kerry’s presidential bids, said voters will be watching Mr. Sanders closely in the next debate.
“Does his energy level change? Does he campaign differently?” she said. “If he maintains a reasonable energy level, it may not change anything for him.”
On Friday evening, after Mr. Sanders was released from the hospital, he dropped off his bags at his hotel and went for a walk in a park with his wife, Jane Sanders.
The two were seen holding hands.
Lawrence K. Altman, Gina Kolata, Lisa Lerer and Jonathan Martin contributed reporting.