A procedure to restore Vice President Dick Cheney's heart to a normal rhythm is being declared a success.

Cheney has been discharged from a George Washington University Hospital Monday night after doctors administered an electrical shock to his heart.

The vice president spent more than two hours at the hospital after experiencing an irregular heartbeat early in the day.

The condition was detected when Cheney was seen by doctors at the White House Monday morning for a lingering cough from a cold. He remained at work throughout the day, joining President George W. Bush in meetings with Mideast leaders.

"During examination he was incidentally found to have an irregular heartbeat, which on further testing was determined to be atrial fibrillation, an abnormal rhythm involving the upper chambers of the heart," said spokeswoman Megan Mitchell.

About 2.8 million Americans have the condition. It occurs when the heart's top chambers, called the atria, get out of sync with the bottom chambers' pumping action. It is not immediately life-threatening, and the heart sometimes gets back into rhythm on its own. Many times, patients aren't aware of an episode of atrial fibrillation.

However, if the irregular heartbeat continues, it eventually can cause a life-threatening complication -- the formation of blood clots that can shoot to the brain and cause a stroke.

Cheney, 66, has a history of heart ailments. He has had four heart attacks, quadruple bypass surgery, two artery-clearing angioplasties and an operation to implant a defibrillator six years ago. In March, he was treated for a blood clot in his left leg. In July he had surgery Saturday to replace the defibrillator which monitors his heartbeat.