President Bush returned to work at the White House Monday after doctors agreed they could stabilize his heartbeat with medication rather than an electric shock procedure. "It's great to be back," Bush told cheering aides in the Rose Garden.

The president's heartbeat had not returned to normal at his release from Bethesda Naval Hospital, but his physician, Dr. Burton Lee, said it did return to normal at midmorning as monitored in the Oval Office."He is in good spirits and anxious to get back to work," said spokesman Marlin Fitzwater. To punctuate Bush's resolve, Fitzwater said the president would meet as scheduled with former Soviet Foreign Minister Eduard Shevardnadze.

Bush said he was not concerned about his condition and did not anticipate changes in his hectic lifestyle or working pace - and his doctors agreed.

"It's not a major league rhythm disturbance," said Dr. Bruce Lloyd, chief of cardiology at Bethesda. He had no qualms about Bush resuming his normal schedule.

"This is a man with a perfectly normal cardiac function and anatomy," added Dr. Allan Ross of George Washington University, who participated in treating Bush for atrial fibrillation. He said the condition inconvenienced Bush "only in the sense that he could not perform at his quite incredible physical peak for his age."

The doctors said they did not know the cause of the irregular heartbeat. "If we knew what triggered it, it would be an easy solution," Lloyd said.

Bush, 66, suffered the irregular heartbeat over the weekend while jogging at Camp David and was evacuated to Bethesda Naval Hospital where the condition persisted despite the prescription of the drugs digoxin and procainamide. Lloyd said there had been no side effects to the medication.

Atrial fibrillation, an irregular heart rhythm, is suffered by an estimated 1.5 million to 2 million Americans.

Fitzwater said Bush's heartbeat had returned to normal at 10:45 p.m. Sunday night but that irregularities returned at 4:45 a.m. Monday. Nonetheless, doctors determined that Bush would not need to undergo an electric shock treatment. Bush had been prepared to briefly relinquish the powers of his office to Vice President Dan Quayle if a shock had been administered.

Bush met with reporters briefly as he left Bethesda. Asked if he needed to change his lifestyle, he replied, "Ask the doctors that, but not as far as I'm concerned." Concerning physical activity, he added, "They said to gradually get back into athletics, but not overdo it."

Lloyd said once the medication is properly adjusted, Bush could resume his exercise regimen "at full speed."

First lady Barbara Bush kept to her schedule Monday, flying to Jupiter, Fla., for an event to promote literacy. The vice president also kept to his schedule.

Bush wore a dark business suit, with a large bandage visible on his wrist, and was walking normally when he arrived at the White House. About 150 staffers gathered in the rain in the Rose Garden to welcome him back.

Fitzwater said Bush's condition would be monitored closely in the White House medical unit.

"We want to assure the American people that the president is in a healthy condition," Fitzwater said on Sunday. "He has not suffered a heart attack."

The irregular heartbeat condition can be caused by factors ranging from a heart attack to simple stress and fatigue. It does not necessarily pose a serious medical threat but can increase the risk of a stroke.