Presidential hopeful Bernie Sanders on Wednesday canceled all appearances and events until further notice after the 78-year-old senator underwent a procedure for an artery blockage.

In a statement Wednesday, the senator’s adviser Jeff Weaver said Sanders “experienced some chest discomfort” during a Tuesday event. Testing found a “blockage in one artery,” and Sanders had two stents inserted, he said.

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

A guide to the Democratic contenders who want to face Trump

Sanders is the oldest presidential candidate seeking to challenge President Donald Trump in 2020. The Vermont independent is three years older than former Vice President Joe Biden, who has led most national and state primary polls despite concerns about his mental sharpness.

Sanders is five years older than the 73-year-old Trump, who is the oldest person to be elected as a first-term president.

The senator had committed to releasing his medical records before the primary voting contests started. During his 2016 presidential campaign, Sanders released a letter from his doctor saying the senator was in good health and did not have a history of heart disease.

Slideshow by Tribune News Service

The senator’s Democratic primary competitors sent him messages of support after his campaign announced the procedure. In a tweet, Sen. Kamala Harris, D-Calif., wished Sanders a “speedy recovery.” She called him a “fighter” and said she looked forward to “seeing him on the campaign trail soon.”

Sen. Cory Booker, D-N.J., also wished his rival a “speedy recovery.”

This is breaking news. Please check back for updates.

CNBC’s Kevin Breuninger contributed to this report.