The impact of time to thrombolytic treatment on outcome in patients with acute myocardial infarction

Objectives-To examine the impact of time to thrombolytic treatment on multiple acute outcome variables in a single trial of thrombolysis in acute myocardial infarction. Design and patients-Mortality and reinfarction rate were measured in 2770 patients with acute myocardial infarction international, dose ranging trial of poloxamer 188. Tc-99m sestamibi infarct size and radionuclide angiographic ejection fraction substudies included 1099 and 1074 patients, respectively. Results-Time to thrombolysis, subgrouped by intervals (< 2, 2-4, greater than or equal to 4-6, and greater than or equal to 6 hours), was significantly associated with infarct size (median 15.0% 18.5%, 22.0%, 18.5% of left ventricle; p = 0.033), mean (Sa) ejection fraction (51.5 (12.0)%, 48.3 (13.9)%, 48.2 (13.3)%, 48.2 (15.0)%: p = 0.006), 35 day mortality (5.7%, 7.1%, 7.9%, 12.5%; p = 0.0004), six month mortality (7.3%, 8.6%, 10.4%, 15.5%; p < 0.0001), and 35 day reinfarction rate (6.1%, 3.2%, 4.0%, 0.9%; p = 0.0001). Conclusions-In this single large trial, the beneficial effect of time to thrombolysis on infarct size and ejection fraction was restricted to treatment given within two hours of symptom onset, while the effect on mortality was evident over ail time intervals. Reinfarction rate was higher in patients treated with earlier thrombolysis.