Impact of time to treatment with tissue plasminogen activator on morbidity and mortality following acute myocardial infarction (the second National Registry of Myocardial Infarction)

Abstract

This study examines the association between time to treatment with thrombolytic therapy and hospital outcomes in patients with acute myocardial infarction (AMI) enrolled in a national registry. A total of 71,253 patients hospitalized with AMI from June 1994 to July 1996 who received tissue plasminogen activator (t-PA) therapy in 1,474 United States hospitals were studied. In this study sample, approximately 39% of patients presented to participating hospitals within 2 hours of acute symptom onset and received t-PA; 36% were treated within 2.1 to 4 hours, 12% between 4.1 to 6 hours, and the remaining 13% thereafter. After controlling for potentially confounding factors, in-hospital death rates increased progressively with increasing delays in time of administration of t-PA. The lowest risk for dying during acute hospitalization was seen for those treated with t-PA within 2 hours of acute symptoms. No significant association was seen between time of administration of t-PA and in-hospital risk of recurrent AMI, myocardial ischemia, cardiogenic shock, major bleeding episodes, or stroke and/or intracranial bleeding. The incidence of sustained ventricular arrhythmias declined with progressively longer time to administration of t-PA. The results of this multihospital observational study suggest that patients with AMI treated earlier with t-PA are significantly more likely to survive the acute hospitalization than patients treated later. These data reinforce the benefits to be gained by treatment with t-PA as soon as possible following the onset of acute ischemic symptoms, and for community-wide efforts to reduce the duration of prehospital delay in patients with acute coronary disease.