RAPID ASSESSMENT OF PLATELET-FUNCTION WITH A MODIFIED WHOLE-BLOOD AGGREGOMETER IN PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY PATIENTS RECEIVING ANTI-GP IIB IIIA THERAPY/

Background The glycoprotein (GP) IIb/IIIa receptor antagonist abcixima b (c7E3 Fab, ReoPro) is approved for use in high-risk percutaneous tra nsluminal coronary angioplasty (PTCA). At present, no ''point of care' ' exists for measuring pharmacological GP IIb/IIIa blockade. To addres s this need, the Chrono-log Whole Blood Aggregometer, which measures p latelet aggregation by electrical impedance, was adapted to test plate let function at the bedside. Methods and Results GP IIb/IIIa receptor blockade, impedance (5 mu g/mL collagen), and turbidimetric aggregatio n (5 and 20 mu mol/L ADP) measurements were obtained on 14 PTCA patien ts who received the standard bolus plus a 12-hour infusion of abcixima b. During abciximab administration, mean GP IIb/IIIa receptor blockade was >91%, and both impedance and turbidimetric aggregation were inhib ited by greater than or equal to 90%. At 12 hours after abciximab trea tment, the mean inhibition of turbidimetric platelet aggregation to 5 and 20 mu mol/L ADP was 65+/-20% and 49+/-14%, respectively, and inhib ition of impedance aggregation was 69+/-12%. GP IIb/IIIa receptor bloc kade was 67+/-8%. At 36 hours after abciximab treatment (n=8), the mea n inhibition of turbidimetric platelet aggregation to 5 and 20 mu mol/ L ADP was 44+/-21% and 30+/-14%, respectively, whereas impedance aggre gation was inhibited by 60+/-14%. GP IIb/IIIa receptor blockade was 57 +/-7%. Conclusions During and at 12 hours after abciximab therapy, imp edance and turbidimetric platelet aggregation to 5 mu mol/L ADP were c omparable and closely correlated with GP IIb/IIIa receptor blockade. H owever, at 36 hours after abciximab treatment, impedance platelet aggr egation more closely paralleled GP IIb/IIIa receptor blockade and indi cated a slower recovery of platelet function than turbidimetric aggreg ometry.