U.S. Senator Bernie Sanders’ campaign announced the presidential candidate experienced some “chest discomfort” on Tuesday and was hospitalized and underwent surgery. He has canceled events until further notice.

Senior Advisor Jeff Weaver in a statement says Sanders, 78, “was found to have a blockage in one artery and two stents were successfully inserted.”

He describes the Vermont Senator as “conversing,” “in good spirits,” and says he will be “resting up over the next few days.”