Seven years ago, Massachusetts mandated that hospitals report on a public database how often they perform minimally invasive heart procedures to open blocked arteries—like angioplasty and stenting—and their death rates from these procedures. That was meant to reduce unnecessary procedures and to lower death rates, but new research from the Harvard School of Public Health and two Boston hospitals indicates that the public reporting system might also be leading to fewer angioplasties in patients who need them the most: those in the throes of a heart attack.