Harry Whittington, the 78-year-old lawyer shot by Cheney, suffered a mild heart attack after a shotgun pellet in his chest traveled to his heart, hospital officials said.
Whittington was immediately moved back to an intensive care unit and will be watched for a week to make sure more of the metal pellets do not move to other vital organs. He was reported in stable condition.
Cheney, an experienced hunter, has not spoken publicly about the accident, which took place Saturday night while the vice president was aiming for a quail. Critics of the Bush administration called for more answers from the Cheney himself.
The furor over the accident and the White House delay in making it public are "part of the secretive nature of this administration," said Senate Democratic Leader Harry Reid of Nevada. "I think it's time the American people heard from the vice president."
Whittington suffered a "silent heart attack" — obstructed blood flow, but without the classic heart-attack symptoms of pain and pressure, according to doctors at Christus Spohn Hospital Corpus Christi-Memorial.
The doctors said they decided to treat the situation conservatively and leave the pellet alone rather than operate to remove it. They said they are highly optimistic Whittington will recover and live a healthy life with the pellet left in place.
Asked whether the pellet could move farther into his heart and become fatal, hospital officials said that was a hypothetical question they could not answer.
Check out the Texas Parks and Wildlife Department's report on Cheney shooting Whittington (.pdf).
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Hospital officials said they were not concerned about the six to 200 other pieces of birdshot that might still be lodged in Whittington's body. Cheney was using 7½ shot from a 28-gauge shotgun. Shotgun pellets are typically made of steel or lead; the pellets in 7½ shot are just under a tenth of an inch in diameter.
The single BB that is lodged in Whittington's heart is minuscule compared to even a penny, reports CBS News correspondent Lee Cowan, but judging from the accident report from Texas Parks and Wildlife officials, the greatest concentration of the blast was right over Whittington's chest.
Cheney watched the news conference where doctors described Whittington's complications. Then the vice president called him, wished him well and asked if there was anything that he needed.
"The vice president said that he stood ready to assist. Mr. Whittington's spirits were good, but obviously his situation deserves the careful monitoring that his doctors are providing," the vice president's office said in a statement.
Whittington has said through hospital officials that he does not want to comment on the shooting. A young man at Whittington's Austin home who identified himself as his grandson said Tuesday he did not have time to talk to a reporter and closed the door.