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 multi ple acute outcome variables in a single trial of thrombolysis in acute myoc ardial infarction. Design and patients-Mortality and reinfarction rate were measured in 2770 p atients with acute myocardial infarction international, dose ranging trial of poloxamer 188. Tc-99m sestamibi infarct size and radionuclide angiograph ic ejection fraction substudies included 1099 and 1074 patients, respective ly. Results-Time to thrombolysis, subgrouped by intervals (< 2, 2-4, greater th an or equal to 4-6, and greater than or equal to 6 hours), was significantl y associated with infarct size (median 15.0% 18.5%, 22.0%, 18.5% of left ve ntricle; 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 th rombolysis on infarct size and ejection fraction was restricted to treatmen t given within two hours of symptom onset, while the effect on mortality wa s evident over ail time intervals. Reinfarction rate was higher in patients treated with earlier thrombolysis.