PREHOSPITAL-INITIATED VS HOSPITAL-INITIATED THROMBOLYTIC THERAPY - THE MYOCARDIAL-INFARCTION TRIAGE AND INTERVENTION TRIAL

Objective.- To determine the effect of prehospital-initiated vs hospit al-initiated treatment of myocardial infarction on clinical outcome. D esign.- Randomized, controlled clinical trial. Setting.- Multicenter s tudy involving 19 hospitals and all paramedic systems in the Seattle, Wash, metropolitan area. Patients.- A total of 360 patients with sympt oms for 6 hours or less, no risk factors for serious bleeding, and ST- segment elevation were selected by paramedics and a remote physician f or inclusion into the trial. They represented 4% of patients with ches t pain who were screened and 21% of those with acute infarction. Inter ventions.- Patients were allocated to have aspirin and alteplase treat ment initiated before or after hospital arrival. Intravenous sodium he parin was administered to both groups in the hospital. Main Outcome Me asure.- The primary endpoint was a ranked composite score (combining d eath, stroke, serious bleeding, and infarct size). The relation betwee n time to treatment and outcome (composite score, infarct size, ejecti on fraction, and mortality) was also assessed. Results.- Initiating tr eatment before hospital arrival decreased the interval from symptom on set to treatment from 110 to 77 minutes (P<.001). Although more patien ts whose therapy was initiated before hospital arrival had resolution of pain by admission (23% vs 7%; P<.001), there were no significant di fferences in the composite score (P=.64), mortality (5.7% vs 8.1%), ej ection fraction (53% vs 54%), or infarct size (6.1% vs 6.5%). A second ary analysis of time to treatment and outcome showed that treatment in itiated within 70 minutes of symptom onset was associated with better outcome (composite score, P=.009; mortality, 1.2% vs 8.7%, P=.04; infa rct size, 4.9% vs 11.2%, P<.001; and ejection fraction, 53% vs 49%, P= .03) than later treatment. Identification of patients eligible for thr ombolysis by paramedics reduced the hospital treatment time from 60 mi nutes (for patients not in the study) to 20 minutes (for study patient s allocated to begin treatment in the hospital). Conclusion.- There wa s no improvement in outcome associated with initiating treatment befor e hospital arrival; however, treatment within 70 minutes of symptom on set-whether in the hospital or in the field-minimized the infarct proc ess and its complications.