Former first lady Barbara Bush was released from a Houston hospital Friday, saying she was "feeling healthy and strong" nine days after undergoing heart surgery. Bush, 83, thanked the doctors and staff at Methodist Hospital as she left with her husband, former President George H. W. Bush. Doctors termed Mrs. Bush's condition, a severe narrowing of the main heart valve, as common in people of her age. The March 4 operation, in which the aortic valve was replaced with a valve from a pig, took about 2 1/2 hours. "This Friday the 13th turned out to be a very lucky one for me, because I was able to go home with George feeling healthy and strong," Mrs. Bush said in a statement.