Patients with acute myocardial infarction who are treated with tissue plasminogen activator (t-PA) or streptokinase have decreased rates of morbidity and mortality when therapy is given between five and 12 hours after acute symptom presentation. Less benefit or even questionable benefit is seen in patients treated with either thrombolytic regimen more than 12 hours after the onset of acute coronary symptoms. Goldberg and associates used an observational database derived from the second National Registry of Myocardial Infarction (NRMI) to investigate the use and timing of thrombolytic therapy after acute myocardial infarction.

The NRMI database was used because published randomized trials have become increasingly generalized to patients treated with thrombolytic therapy in the community rather than a selected controlled trial population. The registry is a voluntary database of patients hospitalized with documented acute myocardial infarction since 1990; data from NRMI-2, which studied patients from June 1994 to April 1996, were used for this study. Twenty-six percent of all acute medical-surgical hospitals in the United States participated in the database.

Of the 71,253 patients with acute myocardial infarction who were treated with t-PA, 7 percent received treatment within one hour of acute pain onset; 32 percent were treated within one to two hours; and 36 percent were treated within two to four hours. Treatment was administered within four to six hours of acute pain onset in 12 percent of patients and within six to 12 hours in 9 percent of patients; nearly 4 percent of patients received treatment sometime thereafter. Those patients who presented to the hospital sooner were more likely to receive t-PA treatment earlier. A clear association was noted between earlier treatment with t-PA and a lower risk of dying during the acute hospitalization.

The authors conclude that early administration of thrombolytic therapy after acute myocardial infarction improves outcome, and that patient delay in seeking medical care is a major impediment to the receipt of thrombolytic therapy. Patients should be educated not to delay seeking treatment so that early use of thrombolytic therapy can be ensured in appropriate patients.