UnitedHealth Group Inc. and Amedisys Inc. representatives are slated to meet with top Justice Department antitrust enforcers in a last-ditch effort to persuade the agency not to challenge their proposed tie-up, according to people familiar with the matter. The high-stakes meeting between the companies and DOJ antitrust leadership, including Assistant Attorney General Jonathan Kanter, is typically the last step before officials decide whether to file a lawsuit. It's often referred to as a 'last-rites' meeting.