A U.S. government program meant to improve medical care and cut costs by penalizing hospitals that repeatedly readmit people with heart failure may have instead increased the risk that the patients would die, a new study suggests.

The policy, called the Hospital Readmissions Reduction Program, was created in 2010 under Obamacare as one of several ways to use Medicare's immense buying power to improve care. Under the program, hospitals were reimbursed less when heart failure patients were readmitted within a month.

It did reduce the number of costly readmissions, according to the study, which was published Sunday by JAMA Cardiology. Yet the number of patients who died rose as well. The findings could indicate an additional 5,000 to 10,000 deaths annually across the U.S., said Gregg Fonarow, the senior author of the paper and professor of cardiovascular medicine at the University of California, Los Angeles.