Administration of abciximab during percutaneous coronary intervention reduces both ex vivo platelet thrombus formation and fibrin deposition: implications for a potential anticoagulant effect of abciximab.

Abciximab (c7E3 Fab, ReoPro), a platelet glycoprotein (GP) IIb/IIIa inhibitor, decreases acute ischemic complications after percutaneous coronary interventions. Recently, abciximab was shown to decrease thrombin generation in vitro in a static system. To assess whether abciximab can decrease fibrin formation in blood from patients, we quantified both platelet thrombi and fibrin deposition by using an ex vivo flow chamber model. We prospectively studied 18 consecutive patients who underwent percutaneous interventions for unstable coronary syndromes. Blood was perfused directly from the patient through an ex vivo perfusion chamber at a high shear rate, thus mimicking mildly stenosed coronary arteries. Perfusion chamber studies were performed when patients were being treated with heparin plus aspirin before the procedure (baseline) and then repeated after the procedure, when patients were on either aspirin plus heparin alone (group 1, no abciximab, control) or aspirin plus heparin plus abciximab (group 2, abciximab treated). Each patient served as his or her own control. Specimens were stained with combined Masson's trichrome-elastin and antibodies specific for fibrinogen, fibrin, and platelet GP IIIa. Total thrombus area and areas occupied by platelet aggregates and fibrin layers were quantified by planimetry. Group 1 demonstrated no significant change in thrombus area before versus after the procedure; in contrast, treatment with abciximab reduced total thrombus area by 48% in group 2 (after the procedure versus baseline, P=0.01). This decline was due to significant reductions in both platelet aggregates (55%, P=0.005) and fibrin layers (45%, P=0.03). The addition of abciximab to heparin and aspirin in patients undergoing coronary interventions significantly decreases ex vivo thrombus formation on an injured vascular surface. Treatment with abciximab appears to reduce both the platelet and the fibrin thrombus components. This finding supports a potential role for GP IIb/IIIa receptor blockade in decreasing fibrin formation in addition to inhibition of platelet aggregation. Thus, potent inhibitors of GP IIb/IIIa may also act as anticoagulants.