Boston Scientific Corp., the world's biggest maker of heart stents, has agreed to pay $22 million to settle allegations the company's Guidant unit reportedly used clinical studies to pay kickbacks to doctors for using its products. Guidant paid physicians $1,000 to $1,500 each to participate in one of four studies it said were designed to assess the performance of pacemakers and defibrillators, the US Department of Justice said in a prepared statement. In reality, the company was paying doctors to select Guidant devices over competing products, the government said. Boston Scientific will enter into a corporate integrity agreement, which requires its cardiac rhythm management unit to disclose payments to doctors on its Web site.