Patency and Reinfarction in Late-Entry Myocardial Infarct Patients Treated with Reperfusion Therapy

Abstract

Patency of the infarct-related vessel is associated with a more favorable long-term prognosis after acute myocardial infarction (AMI). High infarct vessel patency is reported for early reperfusion therapy, but data on patency and its possible effect on clinical outcome are less abundant for patients presenting late after the acute event. The aim of this study was to investigate whether time to reperfusion is related to infarct-vessel patency and clinical outcome. This study compares 268 patients who presented with symptoms of AMI within six hours after the onset of symptoms (Early) with 33 patients who had reperfusion therapy for signs of ongoing ischemia more than six hours after the start of chest pain (Late). At follow-up coronary angiography, flow through the infarct- related vessel was assessed according to the thrombolysis in myocardial infarction (TIMI) classification. Vessels were considered occluded if TIMI flow grade 0 or 1 was present. Follow-up angiography was performed in 95% of patients after a mean of forty-eight days. The infarct-related vessel was occluded in 41% of the late-entry patients (13 of 32), and in 17% of those presenting early (44 of 252), (P=0.01; relative risk [RR] : 2.50; 95% confidence interval [CI]: 1.26 to 6.83). This was associated with a higher rate of recurrent myocardial infarction in late-entry patients: 27% (9 of 33), compared with 9% (25 of 268) in the early group (P=0.005; RR: 2.94; 95% CI: 1.50 to 5.81). Thus, in the present study, late reperfusion therapy (after six hours) was associated with a higher recurrent myocardial infarction rate and a lower infarct vessel patency rate, compared with early treatment of patients.