Early administration of clot-buster drugs may improve outcome for heart attack patients

Tuesday, July 2, 2002

Researchers at Brigham and Women’s Hospital (BWH) have found that emergency medical personnel could accelerate the treatment of heart attack patients by administering the clot-buster drug reteplase (rPA) in the ambulance rather than waiting until the patient reaches the hospital. The findings of The Early Retevase-Thrombolysis In Myocardial Infarction (ER-TIMI) 19 trial are published in the July 3rd issue of the Journal of the American College of Cardiology.

"Most heart attacks are caused by the sudden formation of a clot that blocks the flow of blood to part of the heart muscle," explained the study’s lead author David A. Morrow, MD, of BWH. "Its vitally important to heart attack patients that the blocked artery is reopened as soon as possible to restore blood flow to the heart. The pre-hospital administration of clot-buster drugs by emergency medical system personnel can accelerate this process and may provide these patients with a better chance of recovery."

Specifically, blood clots are composed of a protein called fibrin and platelets from the circulating blood. Clot-busting drugs, called fibrinolytics, aid in dissolving the fibrin component of blood clots, thereby restoring blood flow to the heart muscle. Although fibrinolytics are an important option for treatment of heart attacks, some patients, primarily because of increased risk of bleeding, are not eligible for fibrinolytic therapy.

The immediate goal of the treatment of heart attack patients is reperfusion, or the swift opening of the blocked artery and the restoration of blood flow to the heart muscle. Early reperfusion minimizes the extent of heart muscle damage and preserves the pumping function of the heart. Optimal benefit is obtained if reperfusion can be established in the first four to six hours of a heart attack.

In this study, researchers enrolled more than 300 patients suffering from a heart attack in 20 emergency medical systems (EMS) in North America between May 1999 and July 2001. The time from EMS arrival to the administration of a fibrinolytic was compared between study patients receiving pre-hospital rPA and sequential control patients who received a fibrinolytic in the hospital six to twelve months before the study.

Among study participants, the median time from arrival of EMS to the initiation of the first rPA treatment was approximately 31 minutes. In contrast, the time from EMS arrival to the in-hospital administration of a fibrinolytic for control patients was approximately 63 minutes.

"Although there was some variation in the time to administration of the first rPA across systems, the impact of introducing pre-hospital rPA remained highly significant, even after adjusting for the variability between systems," said Morrow. "That difference of a half hour could make an important difference in how a heart attack patient will fare."

Researchers found that with a straightforward training program, paramedical personnel can act in conjunction with a medical control physician to effectively screen patients with a suspected heart attack and rapidly initiate treatment with rPA for fibrnolytic-eligible patients suffering from a heart attack.

Moreover, in a geographically diverse set of EMS with a large urban representation and door-to-drug times typical of the current experience in North America, administration of pre-hospital rPA reduced the time by approximately 30 minutes, compared with historical performance, and resulted in a 10-fold increase in the proportion of patients treated within 30 minutes after first medical contact.

"Our findings regarding the feasibility of and time savings with pre-hospital administration of rPA are likely to be applicable to a broad range of emergency medical systems in North America," said Morrow.

BWH is a 716-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare System, an integrated health care delivery network. Internationally recognized as a leading academic health care institution, BWH is committed to excellence in patient care, medical research, and the training and education of health care professionals. The hospital’s preeminence in all aspects of clinical care is coupled with its strength in medical research. A leading recipient of research grants from the National Institutes of Health, BWH conducts internationally acclaimed clinical, basic and epidemiological studies.

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