Washington, D.C. ? Vice President Dick Cheney was treated “without complication” Wednesday for an abnormal heartbeat, his office said, making a short visit to a hospital to restore his normal rhythm with an electric shock.

It was the second time in less than a year that Cheney, a 67-year-old with a history of four heart attacks, had experienced and been treated for an atrial fibrillation, an abnormal rhythm involving the upper chambers of the heart. The episode caused the vice president to cancel his attendance at a political campaign event in Illinois.

Sensing a problem early Wednesday, Cheney saw the White House physician, who discovered the vice president was experiencing a recurrence of the irregular heartbeat. Cheney participated in regular morning briefings with President Bush, among other duties, and remained working at the White House until he went to George Washington University Hospital in the afternoon for treatment.

The process took nearly two hours, after which Cheney went home, said Megan Mitchell, a Cheney spokeswoman.

“An electrical impulse was delivered to restore the heart to normal rhythm,” she said. “The procedure went smoothly and without complication.”