Delays in heart attack care erode the difference between two emergency therapies
Angioplasty surpasses clotbuster drugs only when treatment comes quickly
In a perfect world, heart attack patients would get to the hospital within minutes after their symptoms start.
And most would immediately get sent for an emergency angioplasty, which uses a tiny balloon to clear blood clots that are clogging arteries. Study after study has shown that quick access to this life-saving treatment, also called percutaneous coronary intervention, surpasses fibrinolytic (clot-busting) drugs in emergency heart attack care.
But in the real world, the difference between the two therapies may not be so simple.
According to a new analysis by researchers from the University of Michigan Cardiovascular Center, angioplasty only beats clot-busters if theres less than a one-hour difference between the time it takes to get patients from the emergency room door to the angioplasty suite, and the time it takes to start clot-busting drugs.
And in the real world, that swift access to angioplasty doesnt happen nearly as often as it should, says Eric R. Bates, M.D., professor of cardiovascular medicine at the U-M and senior author of the new study published in the October American Journal of Cardiology. Most hospitals still dont have the staff and equipment needed to do angioplasty, and it can take over an hour to transfer a patient to a hospital that does.
The result? "A delay to get an angioplasty means it may not get you all the benefits you read about," says Bates. "If you cant get angioplasty right away, get medical therapy with clot-busting drugs, and then transfer for angioplasty afterward."
Of course, he says, patients can also boost their chances of survival by getting to a hospital promptly after symptoms begin. The biggest delay is often the delay in getting any sort of medical attention, either because patients dont seek help or they dont call for emergency transportation. Half of heart attack patients get to the hospital by car, rather than by ambulance.
Bates, who performs angioplasties on hundreds of patients a year, conducted the meta-analysis of 21 heart attack treatment studies with U-M cardiovascular fellow Brahmajee Nallamothu, M.D., MPH. It is the largest analysis of its kind ever done.
The authors looked at the risk of death, second heart attack and stroke in the six weeks after a heart attack, for patients who received either PCI or thrombolytic therapy. It cross-analyzed that risk with the time delay associated with PCI.
"As the PCI-related time delay increased, the mortality reduction associated with PCI decreased significantly," says Nallamothu. "Overall, the two strategies appeared to become equivalent after a PCI-related delay of 62 minutes."
The results, Bates and Nallamothu write, may explain why the life-saving benefits of angioplasty seen in prospective studies at major medical centers havent always been seen in observational studies in the "real world" where longer delays frequently occur.
Recent data show that it takes about 108 minutes for angioplasty to begin on patients who go directly to a hospital that can do the procedure, and 185 minutes for it to begin when patients first go to a non-angioplasty hospital and are transferred.
By looking at "door-to-needle" time for clot-busting drugs and "door-to-balloon" time for angioplasty, using data from 21 randomized prospective clinical trials, the U-M authors were able to see clearly the effect of time delay on patient outcome.
The bottom line, they say, is that no matter what treatment patients get, they should get it fast.
However, they add that high-risk patients, and those who cannot tolerate clot-busting drugs because of other medical conditions or medications, should still get angioplasty even if the delay is slightly longer. The current study does not adjust for individual patients risk factors, but rather looks at patients in groups based on the results from the particular study they were in.
The new U-M analysis adds fuel to the controversy over how and when hospitals treat heart attack victims, and where patients get sent for treatment.
"Balloon versus drug, and transferring versus treating in house, are big issues for hospitals," Bates notes. "We wanted to step back and get past the hype thats moving everyone toward putting the emphasis on angioplasty and transfer. The momentum is there to give more patients access to angioplasty. But when you look at it, the studies that have shown the big benefits from angioplasty have been somewhat artificial, in comparison with the way things really work."
Hospitals that dont do angioplasty may be reluctant to decide that they should give up a patient and transfer him or her to another hospital. Even when that decision is made, it takes time to get an ambulance ready to go to the receiving hospital, and to get both the angioplasty team and a backup operating room team assembled at the receiving hospital.
Recently, national guidelines and state policies (including in Michigan) have relaxed the requirement for a hospital to have an operating room and cardiac surgeon standing by every time an angioplasty is done. And, Bates says, improved equipment and more experience among angioplasty teams have meant those backups are rarely used.
But compared with Europe, where centralized ambulance and angioplasty services streamline emergency heart attack care, the competitive American system means big delays still happen.
It will take public policy shifts, as well as emergency care protocols based on the best evidence, to correct the problem, Bates says. Thats what Europe has done; a new goal calls for angioplasty patients to begin treatment no later than 90 minutes after they first call for an ambulance.
The American Heart Association and American College of Cardiology are actually working on revising national heart attack care guidelines, and will include goals for reducing the time to treatment of any kind. Bates, along with U-M family medicine associate professor Lee Green, M.D., MPH, serves on the AHA/ACC panel that is developing the guidelines.
"If you want to reproduce the benefits seen in angioplasty studies, then you have to reproduce the times to treatment," Bates notes. "If theres a delay, there may not be a mortality benefit." But, he adds, "The most important message for patients is get to the hospital quickly, because both therapies have been shown to help. The biggest crime is to not get either."
Reference: American Journal of Cardiology, Vol. 92, No. 7, pp. 824-826, October 1, 2003
Kara Gavin | EurekAlert!