Democratic presidential candidate Bernie Sanders underwent emergency surgery after suffering a heart attack, his campaign has confirmed.
The senator was taken to hospital on Tuesday after complaining of chest pain at a campaign event in Nevada.
Doctors operated on Mr Sanders, 78, to remove a blockage in one of his arteries.
Mr Sanders said he was feeling "great" after leaving hospital on Friday.
His doctors said "two stents were placed in a blocked coronary artery in a timely fashion".
A stent is a small mesh tube used to help keep arteries open. Receiving stents is "a minimally invasive procedure", typically with a short recovery time, the US National Heart, Lung and Blood Institute says.
The doctors, Arturo Marchand and Arjun Gururaj, said Mr Sanders's other arteries were "normal".
On Friday, Mr Sanders was well enough to be discharged from Desert Springs Hospital Medical Center in Las Vegas, the doctors said.
The two doctors said that, while Mr Sanders has made "good progress", he has been advised "to follow up with his personal physician".
In an upbeat statement, Mr Sanders said: "After taking a short time off, I look forward to getting back to work."
Later on Friday, he told followers he was "feeling so much better" in a video filmed outside hospital.
Hello everybody! We’re in Las Vegas. I’m feeling so much better.— Bernie Sanders (@BernieSanders) October 5, 2019
Thank you for all of the love and warm wishes that you sent me.
See you soon on the campaign trail. pic.twitter.com/nk3wWIAuE7
With the Democratic presidential contest in full swing, Mr Sanders has vowed to take part in the next live televised Democratic National Committee debate, on 15 October.
As the oldest candidate in the field, Mr Sanders may face questions from his rivals about his fitness to challenge US President Donald Trump for the White House in 2020.
If Mr Sanders were to win the US presidency, he would become the oldest person to hold the office.
When the 2020 US presidential election takes place on 3 November 2020, Mr Sanders will be 79.
Who is Bernie Sanders?
Mr Sanders labels himself a Democratic socialist, which he has defined as someone who seeks to "create an economy that works for all, not just the very wealthy".
He is the longest-serving independent in congressional history, but competes for the Democratic nomination as he says standing as a third-party candidate would diminish his chances of winning the presidency.
When he ran for the Democratic nomination in 2016, he was Hillary Clinton's closest rival.
His 2020 platform has focused largely on his universal health coverage plan, Medicare for All. The policy has also become a key point of contention between Democrats during the last debates, with moderates like Joe Biden criticising it as unfeasible and too expensive.