Platelet inhibition assessed with VerifyNow, flow cytometry and PlateletMapping in patients undergoing heart surgery

IntroductionA substantial number of patients with coronary artery disease undergo cardiac surgery within five days of discontinuing anti-platelet treatment with aspirin and clopidogrel. The aims of this study were to describe the degree of platelet inhibition in patients with dual anti-platelet treatment scheduled for coronary artery bypass graft (CABG) surgery and to investigate whether the measured platelet inhibition correlated to intra- and postoperative risk for bleeding and transfusion requirements.Material and MethodsSixty patients were included. Platelet inhibition was analysed with flow cytometry including phosphorylation status of the vasodilator-stimulated phosphoprotein (VASP-assay) and two bed-side analyzers, VerifyNow-System and PlateletMapping, a modified thrombelastograph. All 60 patients were analysed with VerifyNow and PlateletMapping, and 48 were analysed with flow cytometry and VASP-assay.ResultsThere was a correlation between the ADP-receptor inhibition as measured by VASP-assay and VerifyNowP2Y12 (r = - 0.29, p < 0.05), and between VASP-assay and the expression of P-selectin (r = 0.29, p < 0.05) as measured by flow cytometry when platelets were stimulated with 5 µM ADP. VerifyNowP2Y12 was the only measurement of platelet inhibition correlated to total blood loss (Spearman r = 0.29, p = 0.03) and red blood cell transfusion (Spearman r = 0.43, p < 0.01) requirements, although this might be confounded by aprotinin treatment.ConclusionWe found a modest agreement between the methods for preoperative platelet inhibition, though not for PlateletMapping-MAADP. There was a correlation between preoperative platelet inhibition measured by VerifyNowP2Y12 and surgical blood loss or transfusion requirements. However, for the individual patient, preoperative use of VerifyNowP2Y12 as an instrument to decide bleeding and transfusion risk does not seem helpful.