WASHINGTON (AP) – Vice President Dick Cheney had successful surgery on Saturday to repair aneurysms on the back of both knees and was alert and comfortable after the six-hour procedure, his spokesman said.

Cheney, who has a history of heart problems, was under local anesthesia during the surgery at George Washington University Hospital.

“He will remain in the hospital for up to 48 hours to monitor his recovery. He is expected to resume a regular schedule when he is released to home,” said Steve Schmidt, counselor to the vice president.

After the operation, Cheney was “awake, alert, comfortable,” Schmidt said.

An aneurysm is a ballooning weak spot in an artery that, as blood pulses through, eventually can burst if left untreated. Cheney’s aneurysms, known as popliteal aneurysms, were discovered during his annual physical in July.

Cheney had been scheduled to have only the right knee operated on Saturday but during the surgery his doctors decided to do both at once, Schmidt said. There were no complications.

Cheney had flexible stent grafts put in his knee arteries. During the procedure, the stent graft is threaded through a catheter inserted in the femoral artery at the groin down to the aneurysm site. Fully opened, it’s like a little tube inside the artery, keeping the rushing blood from touching the weakened artery walls.

This is a newer technique for patching aneurysms, and an alternative to rerouting blood flow around the weak spot with a vein bypass.

Dr. Bernadette Aulivola, assistant professor of surgery at Loyola University Medical Center in Maywood, Ill., said about 60 percent of patients with this type of aneurysm in one knee also have it in the other. She said the surgery usually is performed on one knee at a time to avoid complications but that if both procedures went smoothly Cheney should recover quickly.

“When he goes home he should be back to normal, basically back to his baseline activity,” Aulivola said, adding that crutches and wheelchairs are usually not required after this kind of procedure.

Cheney, 64, has had four heart attacks, quadruple bypass surgery, two artery-clearing angioplasties and an operation to implant a special pacemaker in his chest. The pacemaker starts automatically if needed to regulate his heartbeat.

A vascular exam, part of a two-part annual physical Cheney completed in July, identified “small, dilated segments of the arteries behind both knees.”

Cheney’s overall cardio health was judged as good after the first part of the exam, which included a general physical exam, an electrocardiogram and a stress test. The checkup determined that the pacemaker was working well and never had to be activated.

AP-ES-09-24-05 1634EDT