Prehospital administration of the thrombolytic (clot-dissolving) drug reteplase (trade name Retavase®) decreased treatment time by more than 30 minutes at hospitals with average transport times and in-hospital treatment times, compared with patients who received the first dose of the drug at a hospital. Timesavings exceeded 45 minutes at hospitals that had slower treatment times with in-hospital therapy.
Interest in prehospital administration of clot-dissolving drugs has increased with the development of newer agents that can be given as simple injections. Older drugs require lengthy infusion times that make prehospital therapy impractical. Reteplase is given in two injections 30 minutes apart. Some patients in the ER Thrombolysis in Myocardial Infarction 19 (ER TIMI-19) study received both injections before arriving at a hospital, and others received one dose in the field and the other after arriving at a hospital.
“Up to this point, most studies of prehospital thrombolysis have been conducted outside the United States, where patterns of medical care are very different,” says David Morrow, M.D., a cardiologist at Brigham and Women’s Hospital and Harvard Medical School in Boston. “The major prior U.S. trial was conducted in the Seattle area, where there are particularly experienced emergency medical systems (EMS). Our study took into account contemporary patterns of care and current treatment times for heart attack patients in a diverse group of EMS.” The results add to findings from previous studies that indicate earlier treatment improves outcomes after a heart attack, says Morrow. Morrow reported findings from ER TIMI-19, which involved more than 300 patients from 20 geographic areas of North America. After confirmation of the heart attack by paramedics and physicians, each patient received reteplase before or during the trip to a hospital.
Their times to treatment were compared with those from 598 individuals treated in the conventional manner, receiving clot-busters after arrival at a hospital.
When the clot-dissolving drug was given in the field, the time to initial treatment averaged 31 minutes, compared with 64 minutes for patients who started treatment at a hospital. The savings varied according to the time normally required to transport patients to a given hospital (transport time) and the usual delay in treatment after a patient arrives at the hospital (door-to-drug time).
When transport time averaged 20 minutes or less, prehospital thrombolysis saved 23 minutes. The savings increased to an average of 31 minutes for transport times of 20 to 30 minutes, and 48 minutes at hospitals that had transport times longer than 30 minutes.
A similar pattern was observed when door-to-drug time decreased. The savings with pre-hospital administration ranged from 3.5 minutes at hospitals that had a door-to-drug time of 20 minutes or less to a savings of 47.5 minutes at centers that had door-to-drug times longer than 40 minutes.
“Even in areas that are meeting current target door-to-drug times of 20 to 30 minutes, giving the thrombolytic in the field still led to a savings on the order of a half hour,” says Morrow.
The impact of prehospital thrombolytic therapy on patient outcomes requires testing in a larger study, he says. ER TIMI-19 did not include enough patients to determine whether treatment in the field reduces the risk of death or other bad outcomes after a heart attack. Communities interested in prehospital thrombolytic therapy should first carefully evaluate EMS transport times and door-to-drug times at hospitals in the community.
“Cities and hospitals need to look at their infrastructure to see whether they have the resources, training, and experience to offer prehospital treatment,” says Morrow. “We trained the EMS personnel in the majority of systems that participated in ER TIMI-19. With a relatively straightforward training program, we were able to train paramedics and physicians to act in concert to begin treatment earlier than the current standard heart attack treatment in the emergency department. We were also able to treat patients with a very high success rate in terms of correctly identifying patients who are having heart attacks.”
The American Heart Association recommends that anyone experiencing a heart attack call 9-1-1 immediately to access EMS. In addition to providing advanced treatment en route to the hospital, EMS personnel are trained to treat heart attack victims who go into cardiac arrest. Heart attack victims who get to the hospital by ambulance will be treated much faster than those who get a ride or drive themselves.
Co-authors are: Elliott M. Antman, M.D.; Kristin C. Schuhwerk, B.S.; Carolyn H. McCabe, B.S.; Ron M. Walls, M.D.; Eugene Braunwald, M.D.; Assaad Sayah, M.D.; and Michael Waller, M.D.
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Abstract 3428 (Poster)
NR01 – 1364 (SS01/Morrow)