"There is a belief among some clinicians that patients presenting late will not benefit from faster door-to-balloon time (a "cow is already out of the barn" philosophy). We were able to show that door-to-balloon time matters for all patients regardless of time to presentation. Furthermore, we were able to show that door-to-balloon time mattered for both low and high risk patients. In summary, all patients can benefit from shorter door-to-balloon times," said Robert L. McNamara, M.D., M.H.S. from the Yale University School of Medicine in New Haven, Connecticut.
Dr. McNamara noted that it is already well-documented and widely accepted that patients benefit from reducing the overall time between the onset of heart attack symptoms and effective treatment to restore blood flow in coronary arteries. As a result, most hospitals have taken steps to reduce the amount of time it takes to diagnose patients arriving through their emergency departments, activate treatment teams, and begin angioplasty procedures.
However, when patients have been feeling symptoms for a few hours before reaching the hospital, it has not been as clear whether zipping them from the emergency department into a catheterization lab still improves survival.
The researchers used data from a national registry in which hospitals voluntarily enter information about heart attack patients they have treated. The National Registry of Myocardial Infarction (NRMI) is sponsored by Genentech Inc. of South San Francisco, California. In particular, they looked at data on 29,222 heart attack patients treated with angioplasty (percutaneous coronary intervention (PCI)) from 1999 to 2002 at 395 hospitals within 6 hours of alerting health care providers to their symptoms.
Overall, when patients underwent angioplasty (in which a tiny balloon is threaded into a narrowed coronary artery and inflated to reopen blood flow) within 90 minutes of arriving at a hospital, 3 percent died in the hospital. That in-hospital mortality rate rose to 7.4 percent for patients who were in the hospital for more than three hours before being treated.
When the researchers analyzed subgroups of patients who had arrived at a hospital within an hour of reporting symptoms, between one and two hours, or longer than two hours, they still saw the same pattern: within each subgroup, faster action in the hospital meant lower death rates. The same benefits of swift hospital response were seen regardless of whether patients had high-risk factors or not.
The results of this study indicate that while getting to the hospital as quickly as possible is vital, rapid action by the hospital makes just as much of a difference for patients who come in late as it does for those who arrive right away.
"I think the most surprising finding is that mortality decreases with shorter door-to-balloon time to a similar degree for each group, regardless of time to presentation. Many clinicians think that time matters much more for early presenters than for late ones," Dr. McNamara said.
Co-author Harlan M. Krumholz, M.D., S.M., said the nature of heart attacks and how patients perceive symptoms may help explain why quick work in the hospital is important for all patients.
"From my perspective, the reason that time of onset to hospital presentation is not so important is because many patients may not completely occlude their arteries at the time they first recognize symptoms -- and so the actual time of artery occlusion may not be easily predicted from the time it takes them to present to the hospital. Also, some people have waxing and waning symptoms and only present when the symptoms become worse, complicating the determination of the time the heart has been deprived of blood," Dr. Krumholz said.
"The key thing about this study is that it reinforces the value of the increasing national focus on reducing door-to-balloon times and suggests that improving our speed will likely result in many lives being saved," he emphasized.
Dr. McNamara noted that this study looked only at whether patients left the hospital alive. He said it is likely the same benefit would be seen with longer-term survival, but other studies will be needed to document the long-term effects.
Jeffrey J. Cavendish, M.D., F.A.C.C. from the Naval Medical Center in San Diego, California, who was not connected with this study, said the results emphasize the importance of streamlining hospital procedures.
"The main message that this study re-enforces is, not only the concept of "time is muscle," but that "time is life." The sooner we can get patients into the cardiac catheterization lab and unclog the blocked artery causing the heart attack, the lower the likelihood that that patient will die from the heart attack. The National Registry of Myocardial Infarction provides us with an enormous amount of real world data. Dr. McNamara and his colleagues are commended for their vigorous work educating us about where we can and need to do better in treating patients with myocardial infarctions," Dr. Cavendish said.
"Emergency Medical Services and hospitals throughout this country must do better to create a more seamless system to get patients into the catheterization lab in the shortest amount of time. We need a collaborative effort with EMS, Emergency Departments, Nursing, Cardiac Catheterization lab staff and Cardiologists all working together in order to shorten door to balloon times to less than 90 minutes for all patients 24 hours a day, seven days a week," he added.
David A. Halon, M.B., Ch.B., F.A.C.C. from the Lady Davis Carmel Medical Center in Haifa, Israel, who also was not connected with this study, said the results "should spur individual hospitals to examine how each can reduce door-to-balloon time in their own institutional setting."
Dr. Halon noted that patients with at least one risk factor for an adverse outcome of their heart attack appeared to gain the most absolute benefit from rapid angioplasty (PCI) once they reached the hospital. He also noted that each hospital will need to determine how to speed treatment for these patients.
"As pointed out by the authors in the limitations section of the manuscript, although every effort should be made to shorten door-to-balloon time, a registry study does not necessarily point to cause and effect relationships. There are many important factors, both procedural and related to subsequent hospital care, influencing the outcome of primary PCI for acute heart attack. A shorter door-to-balloon time might imply better overall hospital care and benefit correlating with shorter door-to-balloon times may relate to better overall care in those hospitals more efficient at bringing their heart attack patients to rapid PCI," Dr. Halon said.
Earlier studies by this group of researchers found that less than half the hospitals in the United States meet the goal of providing angioplasty within 90 minutes after the arrival of an appropriate heart attack patient. The researchers also outlined the common features of hospitals that successfully reduced door-to-balloon times, including good coordination with ambulance crews to make preliminary diagnoses and a willingness to scramble angioplasty teams early.
Sources quoted in this news release do not report any potential conflicts of interest regarding this topic.
This research was supported by the National Heart, Lung, and Blood Institute
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