The Sabres didn't know Thursday when Numminen will have the procedure. He did not report for team physicals on Thursday and is consulting with team physicians.
"After undergoing examination in connection with his pre-season evaluation, the Buffalo Sabres medical team has determined that (Numminen) requires surgery to correct a cardiac condition," general manager Darcy Regier said in a statement.
Numminen's agent, Don Baizley, was not immediately available for comment.
Numminen, 39, has already had two heart surgeries for an irregular heartbeat, including one in the summer of 2006 after the condition forced him to miss one game and part of another during that year's first-round playoff series against Philadelphia. Regier said the current surgery will be different from the two previous.
"It's early in the process," Regier said. "We'll move along at his schedule and see where he goes with it and what he wants to do."
Regier didn't know how much time Numminen will miss.
Numminen was the team's alternate captain this past season, and finished with 29 points in 79 games.
The native of Finland has had a heart murmur since childhood, and was diagnosed with a dilated aorta in March 2004 when he was with the Dallas Stars. He missed five games because of the condition before being cleared to play.