The U.S. government said it wants to intervene in a lawsuit against St. Jude Medical Inc. in which a former worker accused the heart-device maker of using medical studies to pay kickbacks and boost product usage. The U.S. Attorney's office in Boston launched an industry-wide probe nearly five years ago into whether makers of pacemakers and defibrillators were making improper doctor payments, and had declined in December to get involved in the purported whistleblower suit against St. Jude. In a motion filed in federal court Thursday, however, the government said it now "has good cause to intervene." St. Jude said Friday it objects to the government's motion "and will vigorously defend against the allegations in the lawsuit." The motion was filed in the U.S. District Court for the District of Massachusetts, which must issue an order allowing the government to intervene.