Prehospital-Initiated vs Hospital-Initiated Thrombolytic Therapy
The Myocardial Infarction Triage and Intervention Trial
- W. Douglas Weaver, MD;
- Manuel Cerqueira, MD;
- Alfred P. Hallstrom, PhD;
- Paul E. Litwin, MS;
- Jenny S. Martin, RN;
- Peter J. Kudenchuk, MD;
- Mickey Eisenberg, MD;
- the Myocardial Infarction Triage and Intervention Project Group
Abstract
Objective. —To determine the effect of prehospital-initiated vs hospital-initiated treatment of myocardial infarction on clinical outcome.
Design. —Randomized, controlled clinical trial.
Setting. —Multicenter study involving 19 hospitals and all paramedic systems in the Seattle, Wash, metropolitan area.
Patients. —A total of 360 patients with symptoms for 6 hours or less, no risk factors for serious bleeding, and ST-segment elevation were selected by paramedics and a remote physician for inclusion into the trial. They represented 4% of patients with chest pain who were screened and 21% of those with acute infarction.
Interventions. —Patients were allocated to have aspirin and alteplase treatment initiated before or after hospital arrival. Intravenous sodium heparin was administered to both groups in the hospital.
Main Outcome Measure. —The primary endpoint was a ranked composite score (combining death, stroke, serious bleeding, and infarct size). The relation between time to treatment and outcome (composite score, infarct size, ejection fraction, and mortality) was also assessed.
Results. — Initiating treatment before hospital arrival decreased the interval from symptom onset to treatment from 110 to 77 minutes (P<.001). Although more patients whose therapy was initiated before hospital arrival had resolution of pain by admission (23% vs 7%; P<.001), there were no significant differences in the composite score (P=.64), mortality (5.7% vs 8.1%), ejection fraction (53% vs 54%), or infarct size (6.1% vs 6.5%). A secondary analysis of time to treatment and outcome showed that treatment initiated within 70 minutes of symptom onset was associated with better outcome (composite score, P=.009; mortality, 1.2% vs 8.7%, P=.04; infarct size, 4.9% vs 11.2%, P<.001; and ejection fraction, 53% vs 49%, P=.03) than later treatment. Identification of patients eligible for thrombolysis by paramedics reduced the hospital treatment time from 60 minutes (for patients not in the study) to 20 minutes (for study patients allocated to begin treatment in the hospital).
Conclusion. —There was no improvement in outcome associated with initiating treatment before hospital arrival; however, treatment within 70 minutes of symptom onset—whether in the hospital or in the field—minimized the infarct process and its complications.
(JAMA. 1993;270:1211-1216)
Footnotes
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A complete list of the organizational committee members and individual investigators may be found in Weaver WD, Eisenberg MS, Martin JS, et al. Myocardial Infarction Triage and Intervention Project—phase I: patient characteristics and feasibility of prehospital initiation of thrombolytic therapy. J Am Coll Cardiol. 1990;15:925-931.
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Presented in part at the scientific sessions of the American College of Cardiology annual meeting, Dallas, Tex, April 15, 1992.
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Reprint requests to Myocardial Infarction Triage and Intervention Trial Project Coordinating Center, 1910 Fair-view Ave E, Suite 205, Seattle, WA 98102 (Dr Weaver).
