WWE.com has learned that WWE Hall of Famer Pat Patterson, 65, underwent emergency heart surgery on Sunday night to remove a cyst from his main artery. Following a successful four hour surgery in Montreal, Patterson was in critical condition but remained stable.

Patterson's close friend and WWE Superstar Sylvan visited Patterson after the surgery and said that the Hall of Famer looked well in bed. Patterson's doctors were really positive about his condition, though he will need to be under close supervision for the next few days.

According to Sylvan, Patterson had been experiencing some pain in his back leading up to his surgery that led him to the hospital.

"I met him on Friday for dinner and [Patterson] was complaining about back problems," Sylvan said. "The next day, he spent the day with his sister in Montreal and the pain was worse and getting worse to the point where he couldn't sit down straight and couldn't walk straight; his sister convinced him to go to the hospital. They went to the hospital and the doctors found a big cyst on the main artery [of his heart] inside of his abdomen the size of a baseball, rarely seen that big," he said.

Making his WWE debut in 1979, Pat Patterson was the first-ever Intercontintental Champion. One of the most respected grapplers in sports-entertainment history, Patterson retired from full-time competition in 1984. After transitioning to announcer, Patterson went on to play a significant role in the transformation of WWE from a wrestling company into an international entertainment sensation. Patterson currently works behind the scenes with young talent as both a producer and mentor.

Check back to WWE.com for updates on Patterson's condition.