Evangelist Billy Graham, 89, underwent an elective procedure earlier in the week to update the valve for a shunt which was implanted in 2000 to regulate pressure within his brain.

The procedure, called an aproximal shunt revision, took 28 minutes and was completed without incident, said Asheville neurosurgeon Ralph C Loomis, MD, who replaced the former valve with an externally programmable computer valve.

"He was bright and alert and conscious immediately after surgery and called me by name," Dr. Loomis said of the evangelist's initial recovery.

Mr Graham's procedure was performed at Mission Hospitals near his home in nearby Montreat, North Carolina. He asked the hospital to release information about the procedure and his condition.

Mr Graham has the condition hydrocephalus, a buildup of fluid within the brain which can cause symptoms similar to Parkinson's Disease.

He had been treated at the Mayo Clinic Rochester in 2000 with implantation of the shunt system, which drains excessive fluid from the brain through a small tube down the head and neck and into the abdominal cavity, where it is absorbed by the body.

The rate of flow is controlled by a valve implanted just under the scalp. A recent overall check-up at the Mayo Clinic Jacksonville revealed that the shunt system implanted in 2000 was no longer adequately controlling fluid levels in Mr Graham's brain.

Wednesday's revision involved replacing the valve of the shunt with a new model not available at the time of the original surgery that allows it to be programmed externally to maintain desired fluid levels and pressure.

Mr Graham is listed in fair condition. No date has been given for his release. Barring complication, he is expected to remain at Mission Hospital for a minimum of several days so that the shunt valve can be programmed and regulated before he returns home.

Some of Mr Graham's children - including daughters Anne and Ruth and eldest son, Franklin, and his wife Jane Austin Graham - came to Asheville to visit and were in his room to greet him when he returned from surgery.