Prediction of left ventricular function in patients after acute myocardial infarction treated with primary angioplasty

Abstract

Background: Despite a substantial reduction in in-hospital mortality, the long-term outcomes of patients with acute ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous transluminal coronary angioplasty (PTCA) remain uncertain. The main causes include progressive left ventricle (LV) remodelling and impaired LV systolic function with a decreased ejection fraction (EF). B-type natriuretic peptide testing has recently emerged as an innovative approach that might enhance the echocardiography-based risk stratification after STEMI. The aims of the study included long-term echocardiographic assessment of LV function and remodelling in patients with STEMI treated with PTCA. Additionally, evaluation of the N-terminal pro-brain natriuretic peptide (NT-proBNP) plasma level utility was performed to identify factors at patient discharge which would enable to predict LV dysfunction and remodelling after STEMI at 6-month follow-up.
Methods: Echocardiography was performed in 98 patients at discharge and at 6-month follow-up. The diameters of the heart chambers and indices of LV systolic and diastolic function were measured. Plasma levels of NT-proBNP were measured before PTCA and at 6 months.
Results: Primary PTCA successfully restored normal epicardial blood flow in the infarctrelated Artery (IRA) in 96 patients. At 6 months preserved LV systolic function (median EF 47.5%), decreased LV diastolic function with relaxation abnormalities (E/A < 1.0 and IVRT > 105 ms) and no significant increase in left ventricular end-diastolic diameter (LVEDD) were observed in study population. Multivariate analysis identified low baseline NT-proBNP level, low peak creatine phosphokinase (CPKmax) activity and high EF at discharge as powerful independent predictors of preserved EF at 6 months. LVEDD at discharge, baseline NT-proBNP level and CPKmax correlated with LVEDD at 6 months in the multiple regression model. In multivariate analysis a high NT-proBNP level on admission and low LVEDD at discharge were independent predictors of LVEDD change. Patient groups with reperfusion obtained < and > 3.2 h from symptom onset (the median delay) did not differ with respect to IRA blood flow, infarct size assessed as CPKmax and LVEDD at 6 months. A significant increase in EF was noted only in patients with chest pain duration < 3.2 h. Time-to-treatment correlated with NT-proBNP level at 6 months.
Conclusions: Successful primary PTCA in STEMI influences LV systolic function improvement and effectively prevents LV remodelling at the 6-month follow-up. Low baseline NT-proBNP, low CPKmax and high EF at discharge are powerful independent predictors of preserved EF after 6 months. A high NT-proBNP level on admission and low LVEDD at discharge predict a propensity for LV remodelling. A prolonged time-to-treatment of STEMI results in a lack of significant long-term improvement in LV systolic function and does not seem to have an impact on the occurrence of LV remodelling.