THE EFFECT OF LOW-MOLECULAR-WEIGHT HEPARIN (FRAGMIN) ON MYOCARDIAL NEUTROPHIL ACCUMULATION AND INFARCT SIZE IN A RAT MODEL OF MYOCARDIAL-INFARCTION

Background: Heparin molecules possess immunomodulating properties, whi ch are thought to complement their established antithrombotic activity . The purpose of this study was to evaluate whether the antiinflammato ry properties of low molecular weight heparin (LMWH) can attenuate pol ymorphonuclear neutrophil accumulation and infarct size in a rat model of myocardial infarction. Methods: Myocardial infarction was induced by ligating the left main coronary artery. LMWH (fragmin 500 anti-FXa u/kg) or vehicle (saline) were administered subcutaneously thirty minu tes prior to coronary artery occlusion. Significant anticoaguIant acti vity was attained with LMWH for more than eight hours. Twenty-four hou rs later, neutrophil accumulation and infarct size were determined by measuring left ventricular free wall myeloperoxidase and residual crea tine kinase activity, respectively. Results: As compared with rats adm inistered vehicle, myeloperoxidase activity was insignificantly decrea sed in rats treated with LMWH (1.24 +/-0.28 u/g vs 1.66 +/-0.15 u/g, P =0.16). Infarct size was also not significantly different between the groups (62.48 +/-3.5% and 50.67 +/-7.2% of left ventricular free wall with vehicle and LMWH, respectively, P=0.1). Conclusion: The authors c onclude that LMWH does not significantly reduce myocardial neutrophil accumulation and infarct size twenty-four hours after myocardial infar ction in the rat.