Vanguard Health Systems, two-thirds owned by the Blackstone Group, filed to sell $600 million worth of shares in an initial public offering. No underwriters were listed in the IPO filing with the U.S. Securities and Exchange Commission. The company said in the filing that it will trade under the symbol VHS on the New York Stock Exchange. Vanguard, based in Nashville, Tennessee, owns 26 hospitals in five states, as well as health insurance plans. It had $3.38 billion in revenue during the year ending June 30, 2010, according to the filing. The IPO would be the 10th in the healthcare industry in the past three months, according to Bloomberg data.