In-hospital mortality rates for coronary artery bypass patients in Pennsylvania declined in 2009 to just over 1.5 percent of patients. That's the lowest rate since the Pennsylvania Healthcare Cost Containment Council began reporting the numbers in 1994.

The downward trend in mortality rates has slowed since about 2002. Andrew J. Epstein, from the Perelman School of Medicine at the University of Pennsylvania, said the half a percentage point drop from 2008 is still significant because bypass procedures have been under the microscope of these outcome "report cards" for so long.

"There's been interest in other surgeries and other medical conditions," Epstein said, "but I perceive (bypass) as being one of the, in a sense, grandfathers of this report card effort."

Martin Ciccocioppo, vice president of research with the Hospital & Healthsystem Association of Pennsylvania, said the drop is significant because the patients undergoing bypass surgery have gotten sicker over the years.

"There are fewer of these surgeries being done because the patients who are not as sick are undergoing different types of medical interventions, as well as less invasive surgical interventions, such as the placement of stents," Ciccocioppo said.

According to experts, better post-operative care and surgical techniques, as well as better screening efforts and more alternatives to bypass, are leading to the improved rates.

Of the more than 15,325 patients who had bypass or valve-replacement surgeries in Pennsylvania in 2009, about 5 percent acquired an infection in the hospital and about 15 percent were readmitted to the hospital within 30 days.