Optimization of microvascular reperfusion in acute myocardial infarction

Variations in flow within the spectrum of Thrombolysis in Myocardial Infarc tion (TIMI) grade 3 flow determine the recovery of contractile function in the infarct zone after acute myocardial infarction (MI). The limitation of microvascular reperfusion associated with such impairment may be attributab le to a variety of factors, including distal embolization of small platelet aggregates and direct interactions among platelets, leukocytes and the end othelium. Activated platelets adhere to the endothelium and modulate chemot actic and adhesive properties of endothelial cells; they also bind with leu kocytes and induce up-regulation of the Mac-1 integrin, promoting endotheli al adherence and elaboration of inflammatory cytokines. Mac-1 activity and platelet-leukocyte interactions are increased in patients with acute MI. Th e platelet glycoprotein IIb/IIIa receptor inhibitor abciximab may improve m icrocirculatory function by reducing distal embolization of platelet aggreg ates and decreasing platelet-leukocyte interactions. Recent studies in pati ents undergoing coronary stenting for acute MI have demonstrated that abcix imab is associated with significant decreases in platelet-leukocyte interac tions and Mac-1 expression compared with standard heparin. In a randomized trial of abciximab versus standard heparin in acute MI patients undergoing stenting, abciximab treatment was associated with significant improvements in peak flow velocity and measures of contractile function, including wall motion index and numbers of hypokinetic chords in the infarct zone and glob al ejection fraction. These benefits were accompanied by a significant redu ction in early cardiovascular events. In addition to maintaining large-vess el patency, abciximab improves recovery of microcirculatory perfusion and c ontractile function in acute MI.