A good hospital will get heart attack victims into an operating room and get their clogged artery open within 90 minutes. But a new study shows that shortening that time even further does not significantly lower the risk of dying in the hospital.

The analysis, which measured the so-called door-to-balloon time now widely used to assess the quality of heart attack care, found that shaving additional minutes off the 90-minute goal produced diminishing returns.

The results suggest that more attention should be devoted to getting heart attack victims to the hospital sooner for the treatment, usually with a balloon or stent, known as percutaneous coronary intervention (PCI).

“Door-to-balloon time is a core measure by which hospitals that do PCI treatment are measured. That core metric is not going to go away based on this study, nor should it,” said Dr. Joseph Fredi, an interventional cardiologist at Vanderbilt University Medical Center’s Heart and Vascular Institute in Nashville, Tennessee, who was not involved in the study.

“I hope people don’t take away from it that we can start relaxing and not have to move heaven and earth to not achieve that metric they way hospitals do now,” he told Reuters Health in a telephone interview.

In fact, patients who could not get a PCI within 90 minutes died at a rate that was roughly double that of patients who received treatment in 90 minutes or less, according to the report published in the New England Journal of Medicine.

Coauthor of the new study Dr. Hitinder Gurm of the University of Michigan and the Veterans Affairs Ann Arbor Healthcare System told Reuters Health in a telephone interview, “I don’t think there is anything more we can do at the hospital level.”

Reducing the time in the hospital “is an effort that has been successful, but now we have to look beyond that” and get people to the hospital faster, he said.

“We need to focus on the total ischemic time,” he said, referring to the time the heart muscle is starved of oxygen. “When the patient takes three hours to get to the hospital, the 60 minutes or 90 minutes it takes for treatment doesn’t make as much of a difference.”

“Most of the benefit is in the first two to three hours,” Gurm said. “If we can push the whole effort upstream, that’s where I think we can see the reduction.”

But that’s only a theory, Fredi cautioned. “It may be more complicated than saying if we just restore blood flow, everything will be okay.”

Based on earlier studies showing fewer deaths with faster treatment, doctors and regulators have been pushing for years to treat heart attack patients faster - particularly those with the most damaging type of heart attack, caused by a major coronary artery blockage and called ST-segment elevation for a telltale pattern it produces on a heart monitor.

Gurm said an earlier study of patients across Michigan produced the then-surprising finding that lower door-to-balloon times didn’t lower death rates.

To confirm that finding, Gurm’s team analyzed 96,738 cases of ST-segment elevation collected from 515 U.S. hospitals. They measured the rate of death after 30 days.

During the first year of the study, the typical door-to-balloon time was 83 minutes and the death rate, adjusted for the patient’s risk factors, was five percent. Three years later, the median time had dropped significantly, to 67 minutes, but the death rate was 4.7 percent, an insignificant decline.

“The door-to-balloon time was the low-hanging fruit,” Gurm said. “From the patient’s viewpoint, the heart muscle starts to die the moment the symptoms start, and it keeps dying until the artery’s opened. And most of the delay happens before the patient comes to the hospital.”

If nothing else, “Our findings raise questions about the role of door-to-balloon time as a principal focus for performance measurement and public reporting,” the researchers said.

The study did not include patients who were transferred from a hospital without PCI capabilities or whose treatments were delayed to three hours or longer.

When the researchers repeated their analysis for high risk patients, such as those over 75 or with so much heart damage they were in cardiogenic shock, they found the same pattern - no reduction in the death rate even though the time it took to get treatment declined over the years.

Among the patients who were not getting treatment within 90 minutes, mortality rates showed a slow rise over time, from 6.5 percent during the first full year of the study to 8.9 percent during the fourth year.

“The sicker the patients, the longer the door-to-balloon time. That may be why there was this belief” that reducing the time would produce improvement, Gurm said. “Maybe door-to-balloon time was just a marker of how sick you are.”

SOURCE: New England Journal of Medicine, online September 4, 2013.

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