Platelet hyperreactivity after coronary artery bypass grafting: the possible relevance to glycoprotein polymorphisms. A preliminary report

Coronary artery bypass grafting (CABG) surgery impairs platelet function an d reactivity to a considerable extent. However, variability in the individu al patients' responses makes any generalised statement uncertain. The obser ved variability is nowadays thought to relate to platelet glycoprotein poly morphisms. Our objective was to investigate the association between platele t reactivity and the restoration of platelet functional response to agonist s during the period following cardiosurgical operation and some genetic pol ymorphisms of selected platelet membrane glycoproteins. Platelet reactivity was monitored in 32 IHD patients (56 +/- 8 years) subjected to CABG surger y by means of whole blood impedance aggregometry and concurrently using the platelet function analyser (PFA-100(TM)) at four time intervals: prior to operation (A), 2 h after administration of protamine sulfate (B), 3 days af ter (C) and 7 days after CABG surgery (D). Three important findings were ma de. First, in all patients platelet reactivity became decreased 2 h postope ratively (aggregation with 20 muM ADP reduced by up to 49%, P < 0.02) and v astly increased 7 days after CABG surgery (CTCADP reduced down to 87% of in itial value, P < 0.05, ADP-induced aggregation enhanced up to 167%, P < 0.0 01, and that with collagen up to 131% of the initial value, P < 0.01). Seco nd, the frequencies of the 'prothrombotic' phenotype variants of platelet m embrane glycoproteins were higher in patients referred to as the carriers o f more reactive platelets compared to those with less reactive platelets (G PIa T-807-positive, 50 vs. 28%; GPIIIa PIA2-positive, 27 vs. 21%; GPIb Met( 145)-positive and GPIb VNTR B-positive, 13 vs. 0%. Lastly, the restoration in platelet hyperreactivity in CABG surgery patients was recorded more ofte n in patients who underwent postoperative myocardial ischaemic episode(s), and was associated with significantly higher frequency of the 'prothromboti c' allele T-807 of the collagen receptor glycoprotein Ia (GPIa) in these su bjects (83 vs. 61%). In conclusion, in patients with ischaemic episodes aft er CABG, we demonstrated a fast postoperative restoration of haemostatic ca pacity and evidence of platelet hyperreactivity at 7 days after CABG surger y. The platelet hyperfunction seems to relate to the occurrence of platelet glycoprotein polymorphisms GPIa C-807/T and GPIIIa PIA(1/A2) and may be im portant in predicting postoperative vascular complications in CABG patients .