Rapid assessment of glycoprotein IIb/IIIa blockade with the platelet function analyzer PFA-100 during percutaneous coronary intervention

Background The platelet function analyzer PFA-100 (Dade Behring, Miami, Fla ) evaluates platelet function by determining the time to occlusion of an ap erture in a membrane coated with collagen and adenosine diphosphate or epin ephrine as whole brood flows under shear stress conditions. Platelet aggreg ation causes aperture occlusion, and results are reported as closure time [ CT). Interindividual variability is observed in the level of platelet inhib ition achieved with use of the current abciximab dosing regimen (0.25-mg/kg bolus + 10-mug/min infusion for 12 hours). The relationships between speci fic levels of platelet inhibition and clinical efficacy and safety have not been fully established. Methods and Results We prospectively studied platelet function in 27 patien ts receiving abciximab during percutaneous coronary intervention. This eval uation included determinations of platelet-rich plasma aggregometry, recept or occupancy studies (D3 assay), and CT measurements at baseline and 10 min utes, 4 hours, 12 hours, and 24 hours after the bolus. All patients receive d abciximab, aspirin, and heparin; patients undergoing coronary stent impla ntation received aspirin and ticlopidine after the procedure. CT results we re reported within 10 minutes after initiation of testing. For 96% of patie nts, CT was 300 seconds (maximum CT) immediately after abciximab bolus and remained so throughout the infusion. At 24 hours we observed variable recov ery From platelet inhibition and in 72% of patients CT returned to normal ( less than or equal to 130 seconds). Conclusions Findings with the PFA-100 were similar to results observed with platelet aggregometry and receptor occupancy measurements. Most patients t reated with abciximab exhibit normalized platelet function at 24 hours desp ite moderate levels of receptor occupancy, suggesting dissociation between occupancy and function.