Many patients treated for a heart attack will undergo an angioplasty and receive a coronary artery stent.

Currently, some states are required to publicly report the outcome of those procedures in given hospitals. Now, a new study examines if patients in states with mandatory reporting were less likely to receive these procedures than patients in states which do not have mandatory reporting.

Interventions like angioplasty and placing a stent to open blocked arteries are potentially lifesaving. Massachusetts, New York and Pennsylvania are required to publicly report the outcomes of these procedures.

"That makes hospitals incented to improve and it also gives consumers a chance to look at that information and try to go to the best possible hospital," said Dr. Karen E. Joynt, M.D., of the Harvard School of Public Health.

However, some say making this information public could cause hospitals to avoid taking care of the sickest patients.

"These procedures can sometimes be lifesaving and we really don't want there to be any incentive for a hospital to not provide one of these procedures if it's necessary," said Joynt.

Joynt studied almost 50,000 Medicare patients in Massachusetts, New York and Pennsylvania treated for heart attacks and compared them to similar patients in seven other regional, non-reporting states.

"Patients having heart attacks in public reporting states had about 20 percent lower odds of receiving one of these procedures than patients in other states," said Joynt.

That is because hospitals might not want to do the procedures on sicker patients if it will make their numbers look bad.

"We didn't see any big changes in mortality across these groups suggesting that some of the procedures that were forgone were probably futile but some of the procedures were probably necessary," she said.

Massachusetts started public reporting in 2005.

"In Massachusetts, prior to public reporting rates of this procedure were about the same as they were in the rest of the country but after public reporting kicked in we saw that that rate started to fall," said Joynt. "Massachusetts in particular has done a lot of work to try to mitigate that risk and try to help physicians and hospitals feel comfortable taking care of sick patients."

Michigan hospitals collect their outcomes for internal quality improvement but are not required to report it publicly. Medicare does publicly report outcomes for pneumonia, heart attacks and some surgeries for most hospitals that information is available online.