A source close to Williams' family, speaking on condition of anonymity, confirmed the 82-year-old former Red Sox star had been hospitalized and would undergo the surgery.
"All I know is that he's having a procedure tomorrow, and it's a serious procedure," Red Sox spokesman Kevin Shea said.
"He had a little bit of a situation the other day," Williams' son, John Henry, said in Sunday's Boston Globe, which first reported the story. "The doctors think this is the way to go, and Dad's OK with it. He said, 'If that's the right thing to do, let's do it.'"
Williams had a pacemaker implanted Nov. 6 at Shands Hospital in Gainesville, Fla.
He has been experiencing shortness of breath, and doctors at Shands, after consultation with colleagues around the country, recommended Monday's procedure, the Globe reported.
"It's high-risk surgery because of his age," said Dr. Rick Kerensky, Williams' Florida cardiologist. "It's certainly a surgery with significant risk, but we are hopeful it's going to be successful and we'll see improvement in his condition."
Williams, who had two strokes in the 1990s, was moved from Citrus Memorial in Inverness, Fla., to Shands on Thursday. It was not known at which hospital Williams was hospitalized.
"This is a mechanical problem with a valve, and it needs surgical treatment," Kerensky said. "We measured the reward-risk benefit ratio and agreed this is the way to go."
Williams, who lives in the Crystal River area on Florida's west coast, outside Gainesville, made his last public appearance in Boston when he threw out the first ball at the 1999 All-Star game at Fenway Park.
He was the last major leaguer to bat .400, hitting .406 in 1941.
"I see Ted as a friend, I've come to know him so well, and I just like any friend I'm concerned," said current Red Sox shortstop Nomar Garciaparra. "My prayers are with him."
"Obviously we're very concerned about Ted and wish him the best," Shea said. "We'll be keeping him in our hearts and prayers."
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