President Bush briefly lost consciousness Sunday after he choked on a pretzel while watching a football game on television in his living quarters, the White House said.
After fainting, the president tumbled to the floor from a couch, bruising his lower lip and suffering an abrasion the size of a half dollar on his left cheek, White House physician Dr. Richard Tubb said.
Tubb, an Air Force colonel, said Bush recovered quickly.
"I do not find any reason that this would happen again," Tubb told news agencies in an interview arranged by the White House. "He fainted due to a temporary decrease in heart rate brought on by swallowing a pretzel."
Bush, 55, was found to be in good health during a full physical exam in August.
Aides say he conscientiously adheres to an exercise regimen, running on a treadmill in the White House residence, and while at his Texas ranch or Camp David, routinely racing through three-mile jogs in 21 minutes.
The result of his aerobic workout routine has been a resting pulse rate of 35 to 45 beats per minute, which medical personnel consider extremely low even for a well-trained athlete. A typical resting pulse rate is about 70 beats per minute.
Tubb said Bush's slower heart rate made him more prone to fainting when a nerve was stimulated by the pretzel caught in his throat. The medical term for such an episode is vasovagal syncope, or vasovagal fainting, Tubb said. In such cases, the body sends a signal to the heart via the vagus nerve. This causes a sudden drop in heart rate, which is restored when the person falls.
Such fainting is a common and harmless event that does not signify any underlying illness or have any lasting effects, said Dr. Marshall Morgan, head of the emergency department at UCLA.
"If food goes down the wrong pipe, the natural response is to cough," he said. "It is pretty common for people who are coughing to have a syncope," a brief fainting spell.
It remained unclear Sunday night whether the episode was accompanied by any seizure-like activity that could be a symptom of a more serious matter. Both cardiac rhythm aberrations and seizures are among the transient medical problems that can cause someone to lose consciousness.
Sunday's incident occurred while Bush was alone, watching the National Football League playoff game between the Miami Dolphins and the Baltimore Ravens, the White House said. His wife, Laura, was using the telephone in a nearby room at the time.
"He said it [the pretzel] didn't seem to go down right," Tubb said. "The next thing he knew, he was on the floor."
Bush believes he blacked out for only a few seconds because, as he revived, his two dogs were sitting in the same positions they had been in when he lost consciousness, the doctor said.
"But the dogs were looking at him funny," White House Press Secretary Ari Fleischer told Associated Press.
According to the White House, Bush fainted about 5:35 p.m. EST. About five minutes later, he contacted a nurse on duty at the White House; Tubb was summoned eight minutes later and hurried to the White House to examine the president.
The White House said Bush used an elevator to go from his residence on the second floor of the White House to the ground-floor doctor's office. The medical examination that was conducted there included the use of a heart monitor.
Tubb said Bush's blood pressure and pulse were normal and that he was not taking any medication as a result of the incident.
The doctor said the president had complained Saturday and Sunday that he was "a little off his game" and thought he was coming down with a head cold.
"He had not been feeling well the last couple of days," Tubb said, adding that Bush had exercised rigorously Saturday but had a lighter workout Sunday.
The White House disclosed the incident about 2 1/2 hours after it occurred.
The episode is the second medical incident involving the president in about a month. In early December, the White House acknowledged that Bush had several benign skin lesions removed from his face. The announcement came several days after the procedure, in response to questions from reporters who noticed red marks on the president's face.
Today, Bush is scheduled to leave the White House for a two-day trip to the Midwest and New Orleans to promote trade and its role in stimulating the economy. Tubb said he would examine the president this morning before he left on the trip.
Fleischer said Bush did not plan to alter his schedule: "At this point, he intends to travel."
Gerstenzang reported from Washington and Maugh from Los Angeles.