The scar tissue and fluid reduced Clinton's lung capacity, doctors said after the surgery. They said they expect a full recovery.

Clinton is expected to be in the hospital three to 10 days, the doctors said.

Hospital officials said Clinton was awake and his wife, Sen. Hillary Rodham Clinton of New York, and daughter Chelsea were with him after the four-hour operation.

Clinton, 58, arrived at New York-Presbyterian Hospital/Columbia University Medical Center shortly after 5 a.m. for the procedure to fix the condition physicians described as "quite uncommon."

The former president underwent a quadruple bypass operation in September after doctors said they found extensive heart disease. Some arteries were more than 90 percent blocked.

The low-risk operation was needed as a result of Clinton's open heart surgery. (Full story)

Sen. Clinton said in a written statement that her husband "is doing very well." She praised the doctors and hospital staff and thanked well-wishers for their support.

"This was not a life threatening situation, but of course that didn't stop Chelsea and me from worrying together and praying together," she said. "However, everything went fine, and we're relieved and looking forward to having him come home in the coming days."

Clinton told reporters earlier this week his condition was not serious and he is "doing great."

"There's nothing wrong with me except I have fluid buildup between my ribs and my lung, and it affects my breathing," he said.

"It's not a dangerous procedure unless something totally unpredictable happens," he said. "It's not useful to sit around and worry about things you have no control over. I want to be able to breathe again fully."

"This is a relatively low-risk procedure, and we expect full functional recovery in a limited amount of time," Dr. Joshua Sonett said before he performed the surgery Thursday.

"What has happened here is an extremely unusual result of a common process," said Dr. Craig Smith, who performed Clinton's bypass operation. Smith said that in more than 6,000 bypass surgeries he has seen less than 10 who developed Clinton's condition.

Recently, Clinton traveled with former President George H.W. Bush to South Asia to survey damaged caused by Indian Ocean tsunamis.

Dr. Alan Schwartz, a cardiologist who treated Clinton after his bypass surgery, said Clinton's trip to Asia neither caused nor worsened his condition.

Schwartz said the former president has embarked on a vigorous exercise program, walking four miles a day when he is at home in Chappaqua, New York.

He said that Clinton passed a stress test recently with "flying colors" but that he had begun to feel some discomfort.

"He had noticed over the past month or so that on steep hills he was getting winded a bit more easily," the doctor said. "At the same time he was beginning to feel a bit of discomfort."

Source: Agencies