The University of Pennsylvania Health System agreed to pay $845,000 to settle allegations that it improperly billed Medicare for unnecessary stent procedures at Pennsylvania Hospital between 2008 and 2012, the U.S. Attorney's Office for the Eastern District of Pennsylvania said Thursday.

Federal officials investigated after Penn voluntarily reported the actions by  two interventional cardiologists who no longer work at Pennsylvania Hospital. After Penn discovered the problems, the health system implemented a new quality assurance program in the Pennsylvania Hospital cardiac catheterization lab, the U.S. Attorney said.