Massachusetts U.S. Sens. Edward Markey and Elizabeth Warren are among several political leaders who are attacking the leader of a troubled health care system for refusing to comply with a subpoena to appear before a Senate committee. Lawyers for Steward Health Care CEO Ralph de la Torre said Wednesday that a federal court order prohibits him from discussing anything during an ongoing reorganization and settlement effort. The Senate committee is investigating the Dallas-based hospital company's bankruptcy. Warren and Markey said Thursday that de la Torre is trying to avoid accountability. The company has been trying to sell its Massachusetts hospitals, but two closed on Saturday.