The head coach was taken to hospital yesterday after becoming light-headed during a round of golf in Charlotte.
A statement from the team said: "Our focus at this time is Coach Fox's health and well-being. We extend our thoughts and well-wishes to him for a full and speedy recovery.
"Coach Fox was advised by doctors months ago that his defective aortic valve would require this procedure following the 2013 season. As part of his trip to North Carolina over the bye week, he had a preoperative appointment on Thursday with his doctor, who informed him to seek medical attention immediately if he felt any discomfort.
"On Saturday, Coach Fox began feeling light-headed while golfing with friends. He was taken to a hospital, where testing revealed he needed to have this procedure as soon as possible. The club will announce its interim head coach as soon as that decision is finalised."
The Broncos face the San Diego Chargers next weekend.