Sen. Bernie Sanders (I-VT) underwent emergency heart surgery, installing two stents in an artery, and has canceled all campaign events “until further notice,” his campaign announced Wednesday morning.

Sanders’ Senior Advisor Jeff Weaver said in an emailed statement that Sanders, 78, “experienced some chest discomfort” during a campaign event on Tuesday. A medical evaluation determined that he had a blockage in an artery, and two stents were “successfully inserted.”

Weaver said Sanders conversing and “in good spirits.” However, they are canceling all of his campaign activities until further notice.

The statement reads:

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. 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.

According to the doctor’s note Sanders released in 2016, Sanders has no history of heart disease.