President Clinton lay recuperating at New York-Presbyterian Hospital late yesterday following a quadruple heart bypass surgery that doctors described as routine and apparently successful.

“He is recovering normally,” said Dr. Craig Smith, the chief surgeon on the operation performed. “Right now everything looks straightforward.”

Mr. Clinton had complained of shortness of breath and tightness in his chest but had not suffered a heart attack when he was admitted to the hospital on Friday, doctors said.

A test had revealed a dangerous blockage in key blood vessels that, without the bypass operation, likely would have triggered “a substantial heart attack in the near future,” said Dr. Allan Schwartz, the hospital’s chief of cardiology.

“In several of the vessels, the blockage was well over 90%,” Dr. Schwartz said.

Doctors said that Mr. Clinton, 58, could leave the hospital by week’s end and that a full recovery could take two to three months. They said that Mr. Clinton’s heart was undamaged and that he could expect “normal longevity.”

“He is generally extremely healthy,” Dr. Schwartz said.

Senator Clinton and the Clintons’ daughter, Chelsea, said in a statement yesterday that they were grateful to hospital staff and to well-wishers around the country.

“These past few days have been quite an emotional roller-coaster for us,” they said in the statement. “The president’s optimism and faith will carry him through the difficult weeks and months ahead – of that we have no doubt.”

The Clintons had stayed up late together on Saturday talking and playing games. Just before the surgery, Mr. Clinton had seemed “in a good mood and ready to proceed,” Dr. Smith said.

Dr. Smith said that, as with most bypass surgeries, there were “anxious moments,” but added that there had been nothing “outside the realm of routine.”

A bypass, a relatively common operation, involves taking blood vessels from different areas of the body and using them to circumvent blocked arteries connected to the heart. For Mr. Clinton, a team of three surgeons took blood vessels from his chest and his leg.

During the operation, doctors stopped Mr. Clinton’s heart for 73 minutes.

For several months Mr. Clinton had experienced shortness of breath but didn’t take it “seriously,” his doctors said. The doctors said that he attributed the condition to an intermittent exercise routine and acid reflux.

Mr. Clinton then felt an episode of “discomfort” last week, the doctors said, leading him to visit a Westchester hospital.

Doctors said that they delayed operating on Mr. Clinton, who also had been treated for high cholesterol, only because he was taking a blood thinning medication. The doctors said they waited for the drug to clear his system in order to avoid a risk of excess bleeding.

Mr. Clinton’s surgery came just as he had planned to campaign for Senator Kerry in the two months remaining before the presidential election. Mr. Clinton reportedly had an in-depth phone conversation Saturday from his hospital room with Mr. Kerry about campaign strategy.

Doctors yesterday shied away from saying when Mr. Clinton would be ready to resume making political appearances.

“I would encourage him to resume all activities, including campaigning, as we both deem appropriate,” Dr. Schwartz said. “He will gradually resume an entirely normal exercise and work schedule.”

Dr. Smith also hesitated from making predictions, noting that “after all, this is not the average person.”

After his release, Mr. Clinton will be placed on a regimen of exercises and a new diet, the doctors said. A diet of restricted salt and low saturated fats will “play a major role in preventing recurrence,” Dr. Schwartz said.

Comedians used to mock Mr. Clinton for devouring fast food, but he looked trim at the Democratic convention in July.

The Clintons directed well-wishers to the Clintonfoundation.org Web site, which last night was full of postings from fans of the president wishing him a speedy recovery.