New York Yankees manager Aaron Boone is taking an immediate medical leave of absence to have surgery to get a pacemaker, the team announced Wednesday.

Boone, 47, who had open-heart surgery in 2009, said in a statement that he's had mild symptoms of lightheadedness, low energy and shortness of breath over the past six to eight weeks. He said further tests in New York prior to spring training indicated he had a low heart rate, necessitating the surgery, which will be performed Wednesday at St. Joseph's Hospital in Tampa, Florida.

"My faith is strong, and my spirits are high," Boone said in a statement released by the team. "I'm in a great frame of mind because I know I'm in good hands with the doctors and medical staff here. ... They are confident that today's surgery will allow me to resume all of my usual professional and personal activities and afford me a positive long-term health prognosis without having to change anything about my way of life."

Boone, entering his fourth season as manager of the Yankees, said he looks forward "to getting back to work in the next several days."

Bench coach Carlos Mendoza took over as acting manager for Wednesday night's exhibition against Toronto in Tampa.

"It's a necessary step,'' general manager Brian Cashman said of Boone's surgery. "It's something that's not avoidable and needs to be taken care of, but he has no fear and I know he's just in great hands and it's just a temporary timeout. He looks forward to getting back to doing what he does best and doing what he loves, which is baseball.''

Cashman said that, at first, he was alarmed by the news, but was "comfortable" upon talking to Boone about the surgery.

"When you hear 'pacemaker,' it kind of sets off a lot of alarms of concern," Cashman said. "... No one's going to do more research than the person that's going to be going through this, and I felt so comforted by the way he communicated with me on it that he put me at ease."

Yankees owner Hal Steinbrenner said "the thoughts of the entire organization are with Aaron and his family" in a statement released by the team.

"Aaron leads our players, coaches and staff with a rare combination of work ethic, intelligence and a genuine concern for others," Steinbrenner said. "Our only priority at this time is Aaron's health and well-being, and we will support him in every way throughout his recovery."

Boone played in the major leagues from 1997 to 2009 and was an All-Star for the Yankees in 2003, the year his 11th-inning home run off Boston's Tim Wakefield in Game 7 of the AL Championship Series won the pennant for New York. He is a third-generation major leaguer; his grandfather Gus, father Bob and brother Bret also played in the big leagues, and his nephew Jake is a minor leaguer in the Washington organization.

ESPN's Marly Rivera and The Associated Press contributed to this report.