Former US President Bill Clinton has had another operation, six months after his quadruple heart bypass surgery.
Doctors say Mr Clinton is expected to make a full recovery
Mr Clinton, 58, had fluid and scar tissue removed under general anaesthetic at a New York hospital.
"Bill Clinton is out of surgery and resting comfortably," a hospital statement said. Mr Clinton's office said the surgery was "successful".
The procedure is sometimes necessary after heart surgery, but is rare. Doctors say it is low-risk.
Mr Clinton is expected to spend between three and 10 days at New York Presbyterian Hospital/Columbia University Medical Center.
A news conference on Mr Clinton's condition is expected later.
On Wednesday, Mr Clinton was in Florida at a charity golf tournament to raise money for victims of the Asian tsunami.
"I'm just grateful for every day when the sun comes up. But it is not a dangerous procedure, unless something totally unpredictable happens," he said.
The scar tissue had formed as a result of fluid build-up, causing a compression of the left lung and some discomfort to Mr Clinton.
Doctors at the hospital said before the surgery that the procedure was not "medically urgent" and Mr Clinton's activities had not contributed to his condition.
Mr Clinton's doctors have described the procedure as routine and say he should make a full recovery.
The former president underwent surgery in September after complaining of suffering pains in his chest and breathing difficulties.
Doctors said he had been in imminent danger of a major heart attack before that operation.