Vice President Dick Cheney, 60, checked himself into the hospital in Washington on Monday to clear a partly blocked artery after he complained of chest pains. And out he walked on Tuesday. Asked by a reporter how he felt, Cheney replied "Good." Wednesday, it was announced, he is returning to work. Doctors at George Washington University said that a coronary artery that was opened last November had narrowed again by 90% because of scar tissue and that Cheney's tube was reopened with a balloon angioplasty. They added that he did not suffer a new heart attack (he has had four in the past). Cheney awoke at about 7 a.m. Tuesday and was "antsy" to leave the hospital, senior aide Mary Matalin told the Associated Press. Various cardiac enzyme tests showed no damage to his heart muscle, and "multiple EKGs have been unchanged," she said.