Former secretary of state Henry A. Kissinger, 58, was in "excellent condition" yesterday after a 4 1/2-hour heart operation, his Boston surgeons said.

A Massachusetts General Hospital team performed a triple-bypass heart operation on Kissinger to treat diseased arteries that threatened his health. The surgeons said they expected him to make a complete recovery.

The globe-traveling diplomat, who served in the Nixon and Ford administrations, remained heavily sedated late yesterday, and was not expected to be fully awake until this morning.

"We're all very pleased thus far," Dr. W. Gerald Austen, the hospital's chief of surgery and Kissinger's personal physician, said at a news conference. "I think that we all agree that the major risk is over with the surgery being completed. There is still some risk over the next 24 hours, but a very small risk."

Hospital spokesman Martin Bander said by telephone that Kissinger is likely to be hospitalized for about two weeks. Kissinger told reporters beforehand that he expected to restrict his normally busy schedule over at least the next six weeks.

Among the well-wishers calling him before the operation were President Reagan and former president Gerald R. Ford.

Kissinger joins more than 100,000 other Americans who have coronary artery bypass surgery each year, at a cost of about $15,000 each. Massachusetts General is a major center, with 650 such operations annually, Bander said.

The surgery has become an increasingly common operation, as the estimated risk of dying from the surgery has fallen nationwide to less than 2 percent. But within the medical commmunity there has been an ongoing controversy about the long-term benefits in terms of improved survival and whether other medical treatment should be attempted instead of surgery.

Bander said that physicians at the hospital decided the operation was required after tests Monday. The surgery confirmed that one major coronary artery was "totally blocked" and two others were "significantly narrowed."

Dr. Mortimer J. Buckley Jr., chief of the hospital's cardiac-surgical unit, said this created the equivalent of a "dangerous situation." The restricted blood flow can significantly increase the risk of a heart attack and sudden death.

In yesterday's surgery, Bander said about 18 inches of the saphenous vein in Kissinger's right leg were removed and used to "construct detours" around the blocked portions of the coronary arteries.

Dr. Peter Frommer, acting director of the National Heart, Lung and Blood Institute, said yesterday that the triple-bypass surgery had become "very common" and that "many physicians would consider three-vessel disease a clear indication" for surgery.

Frommer emphasized that he was not speaking about the specifics of Kissinger's case, but noted that a federally sponsored conference showed that there is some scientific evidence "suggesting improved life expectancy." He added, however, that researchers still say that there should be confirmation from further studies that this is so.

Kissinger sought medical help last week after complaining of a pain in his shoulder, and was apparently unaware of any hidden heart disease.

He joked with reporters on Tuesday that it would not affect his life style. But Buckley said yesterday that the 5-foot-8, 203-pound Kissinger needs to lose weight, a prospect that he acknowledged would need to be "negotiated."