Harry Whittington, 78, was recovering and will be monitored for seven days to make sure more bird shot doesn't move to other organs or move to other part of his body, hospital officials said.
"However some of the bird shot appears to have moved and lodged into part of his heart in what we would say is a minor heart attack," said Peter Banko, administrator at Christus Spohn Hospital Corpus Christi-Memorial.
Banko said there was an irregularity in the heartbeat caused by a pellet, and doctors performed a cardiac catheterization. Whittington expressed a desire to leave the hospital, but Banko said he would probably stay for another week to make sure more shot doesn't move to other organs or to other part of his body.
David Blanchard, chief of emergency care, called it "a silent heart attack, an asymptomatic heart attack. He's not had a heart attack in the traditional sense."
Doctors left the birdshot in place and said he could live a healthy life with it there.
Check out the Texas Parks and Wildlife Department's report on Cheney shooting Whittington (.pdf).
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White House physicians who attended to Whittington at the scene after Cheney accidentally shot him were involved in the treatment, the officials said.
The vice president's office said in a statement that Cheney spoke with Whittington on Tuesday afternoon and said he "stood ready to assist." The statement said Whittington's "spirits were good."
Whittington had initially been placed in intensive care after the accident Saturday evening. He had been moved to a "step-down unit" Monday after doctors decided to leave several birdshot pellets lodged in his skin rather than try to remove them.
A Texas Parks and Wildlife Department report issued Monday said Whittington was retrieving a downed bird and stepped out of the hunting line he was sharing with Cheney. "Another covey was flushed and Cheney swung on a bird and fired, striking Whittington in the face, neck and chest at approximately 30 yards," the report said.
The department found the main factor contributing to the accident was a "hunter's judgment factor." No other secondary factors were found to have played a role.
The department gave Cheney and Whittington warning citations for breaking Texas hunting law by failing to buy a $7 stamp allowing them to shoot upland game birds. A department spokesman said warnings are being issued in most cases because the stamp requirement only went into effect five months ago and many hunters weren't aware of it.
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.
"There are no plans at this time for any public events where the vice president might speak publicly" about the accident, the vice president's office said Tuesday, CBS News correspondent Peter Maer reports.
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."
Democratic Sen. Chuck Schumer called on Cheney to hold a press conference to discuss the shooting incident.
"Though no one doubts that the hunting mishap was an accident, it is astonishing that you have let three days go by without speaking directly to the public about it," Schumer, D-N.Y., said in a letter to Cheney.
The accident wasand even at the White House early Tuesday, before news surfaced about problems with Whittington's heart.
Later Tuesday, White House spokesman Scott McClellan, facing more questions about Cheney from reporters, served notice that he intends to move on.
"If you all want to continue to focus on this you can spend your time on it. We're going to keep focusing on the pressing priorities of the American people," he said.
Hospital officials said they notified the White House of the change in Whittington's condition late in the morning. McClellan's mood was much more serious in an afternoon press briefing shortly before the hospital publicly updated Whittington's condition.
Katharine Armstrong, owner of the ranch where the shooting occurred, said Whittington made a mistake by not announcing that he had walked up to rejoin the hunting line after going to retrieve his bird, and Cheney didn't see him as he tried to down a bird.
But the accident raised questions about Cheney's adherence to hunting safety practices and the White House's failure to disclose the accident in a timely way.
While some hunting experts said Whittington should have made his presence known, Cheney apparently broke the number one rule of hunting: always know what you're firing at.
"We always stress to anybody that before you make any kind of a shot, it's incumbent upon the shooter to assess the situation and make sure it's a safe shot," said Mark Birkhauser, president-elect of the International Hunter Education Association and hunter education coordinator in New Mexico.
"Once you squeeze that trigger, you can't bring that shot back."
Mr. Bush was told about Cheney's involvement in the accident shortly before 8 p.m. Saturday — about an hour after it occurred — but the White House did not disclose the accident until Sunday afternoon, and then only in response to press questions.