Prehospital diagnosis and treatment of acute myocardial infarction: A critical review

Abstract

Early lysis of an occluding thrombus in the setting of an acute myocardial infarction (AMI) results in improved left ventricular function,1‘4 reduction in mortality,5* 6 and enhancement of survival.7,8 The Intravenous Streptokinase in Acute Myocardial infarction (ISAM) study group9 found that patients treated within 1.5 hours of the onset of chest pain had significantly shorter time to peak creatinine kinase interval, a smaller area under the creatine kinase (CK)-MB curve, and higher global or infarct-related regional ejection fractions compared with patients treated 1.5 to 4 hours after AMI. Fine et al.1° found significantly smaller infarct size when patients with anterior wall AMIs were treated within 2 hours compared with 2 to 4 hours from time of symptom onset. In a placebocontrolled, randomized trial using intravenous streptokinase (SK), the Gruppo Italian0 per lo studio della Streptochinasi nell’ Infarto Miocardico (GISSI) group” found an 18 % reduction in overall mortality in SK treated patients. Although patients treated within 3 hours had a reduction in hospital mortality of 23 o/O, the most striking benefit was observed in patients who received intravenous SK within 1 hour of AMI symptom onset. These patients with very early treatment had a reduction in hospital mortality of 47 Scl and a survival advantage that persisted at the l-year follow-up. Thus maximum benefit from intravenous thrombolytic therapy appears to be obtained in those patients treated within 1 to 2 hours of symptom onset. Unfortunately, only a small proportion of patients receive thrombolytic therapy within this time