Vice President Cheney, who has had four heart attacks, underwent three hours of tests at George Washington University Medical Center yesterday after he experienced shortness of breath and was coughing up phlegm.

Doctors said the tests did not show any heart abnormalities, just a bad cold. He spent last night at his official residence in Washington.

"I feel fine," Cheney, 63, said as he walked out of the hospital and into his black Suburban.

Mary Matalin, Cheney's former counselor, said the battery of tests was done "out of an abundance of caution."

"His work has not been and will not be interrupted," she said.

Cheney and his wife, Lynne, who accompanied him to the hospital, planned to go ahead with a social engagement yesterday evening.

The vice president spent much of the past year on the road as a fundraiser and campaigner for the Bush-Cheney ticket and for Republican congressional candidates.

The White House released a statement by Cheney's longtime cardiologist, Jonathan S. Reiner, saying that the tests had ruled out "any cardiac cause for the vice president's symptoms," and had ruled out pneumonia.

"The vice president likely has a viral, upper respiratory infection," the statement said.

In other words, an infection of the nose and throat -- a cold. Nevertheless, the episode drew attention to Cheney's health as he and an apparently vigorous President Bush prepare for their second term.

Bush skipped the physical that he usually undergoes each August. A knee condition has prevented Bush from running, and he has had several spills while mountain biking, a sport he took up after his jogging was curtailed.

Asked by The Washington Post last week why Bush still has not undergone a physical, White House press secretary Scott McClellan said: "Like other Americans, the president discussed the timing of his physical with his doctor, and they felt it was perfectly fine to do it sometime after early November. He had a busier travel schedule the last few months than the previous three years. The president is physically fit and in great health. If his doctor felt he needed to do it sooner, he would have."

Aides said Cheney uses an elliptical trainer and kept up his regimen on the campaign trail. Sometimes the exercise machine was seen being unloaded from Air Force Two, and sometimes it was ready for the vice president in his hotel room. Cheney maintains a diet that emphasizes fish, buffalo and salad, aides said.

Cheney's aides said he developed his cold last week during an annual pheasant-hunting trip to South Dakota. Among those he hunted with were Sen.-elect John Thune (R-S.D.), who unseated Senate Minority Leader Thomas A. Daschle (D-S.D.) in the Nov. 2 election. Cheney's chief of staff, I. Lewis Libby, also went along on the trip.

On Friday, Cheney sat in the front row during Bush's joint news conference with British Prime Minister Tony Blair in the East Room of the White House. Matalin spoke with Cheney yesterday morning, and he "wanted to talk about the campaign," she said.

After having breathing problems in the morning, Cheney consulted Reiner, director of George Washington's cardiac catheterization laboratory. According to Matalin, Reiner told Cheney to "come in and get the tests." Cheney did not go in an ambulance but left from his residence -- at the Naval Observatory on upper Massachusetts Avenue NW -- in his customary motorcade. One of his daughters, Liz Cheney, joined her parents at the hospital. She told Matalin that Cheney was in his street clothes and walking from room to room for the tests, which included blood work and an electrocardiogram.

In June 2001, doctors at GWU Medical Center inserted a special pacemaker, known as an implantable cardioverter defibrillator into Cheney's chest to help regulate his heartbeat. The pager-size device would administer a shock to the heart if abnormal rhythms occurred; the heart then would resume a normal pace.

Matalin said doctors read the device yesterday and found no abnormal activity over the previous 90 days, the period it records.

Medical experts said the concern was warranted because -- given Cheney's history of heart disease -- a possible cause of his breathlessness was congestive heart failure. In that condition, the heart cannot pump forcefully enough to keep up with the amount of blood returning to it from the rest of the body. When that happens, blood backs up in the lungs, causing a sensation of shortness of breath.

Cheney has had a long history of heart problems, dating to 1978, when he suffered his first heart attack. Since then, he has had three more. The most recent was a mild one in November 2000, when the outcome of the presidential election was hanging on a few hundred votes in Florida.

Over the years, Cheney has undergone a series of treatments to clear his clogged arteries. He had a quadruple bypass in 1988 after suffering his third heart attack and had a springlike wire tube known as a stent implanted in an artery in November 2000 to hold it open. He returned to the hospital for further treatment to the same artery in March 2001.

After Cheney's last annual checkup, in May 2004, doctors reported that the pacemaker was working fine and had never been activated, indicating that he had not suffered from arrhythmia.

If Cheney were to die in office or become incapacitated, Bush would have the right to nominate a new vice president, in accordance with the 25th Amendment, which went into effect in February 1967. The only stipulation is that the president's candidate be confirmed "by a majority vote of both houses of Congress."

The amendment was last invoked in August 1974, when President Gerald R. Ford, after President Richard M. Nixon's resignation, nominated Nelson A. Rockefeller for vice president.

Staff writer David Brown contributed to this report.

Vice President Cheney and his wife, Lynne, leave George Washington University Medical Center yesterday after he had three hours of tests.