Abstract
Viscoelastic tests provide a dynamic assessment of coagulation, by exploring the time to clot formation and the clot strength. Using specific activators or inhibitors, additional factors can be explored, like the fibrinogen contribution to clot strength. Since the early days, various attempts have been done to measure platelet function with viscoelastic test. In general, the difference between the maximum clot strength and the fibrinogen contribution is considered an index of platelet contribution. However, this parameter does not clearly split platelet count from function; additionally, the extensive thrombin generation of standard activated viscoelastic tests activates platelet through the protease activated receptors, bypassing the other pathways. For this reason, standard viscoelastic tests cannot be used to assess platelet reactivity under the effects of aspirin or P2Y12 inhibitors. To overcome this limitation, a specific test was developed (thromboelastography platelet mapping). This test has been compared with the gold standard of light transmission aggregometry and with other point-of-care tests, with conflicting results. In general, the use of viscoelastic tests to assess the effects of antiplatelet agents is still limited. Conversely, platelet contribution to clot strength in the setting of coagulopathic bleeding is considered an important parameter to trigger platelet transfusion or desmopressin.
Highlights
Viscoelastic tests provide a dynamic assessment of coagulation, by exploring the time to clot formation and the clot strength
The MA at standard TEG was directly correlated with whole-blood lumiaggregation after stimulation with collagen, ristocetin, arachidonic acid, and ADP. These results are certainly reflecting the fact that the inhibition of the terminal receptor of platelet aggregation GPIIbIIIa has an effect on viscoelastic tests (VET)-based clot stiffness, and that in absence of anti-platelet agents the MA/MCF correlates with platelet aggregation
The need to provide a measure of platelet aggregation under the effects of P2Y12 inhibitors became more and more important with the wide diffusion of double anti-platelet therapy (DAPT)
Summary
Until the blood remains in the fluid phase, no movement is transmitted to the suspended pin nor the rotating pin is braked in its movement This corresponds to the flat line that is the first part of both the TEG and the TEM tracings, whose normal duration varies from 1 to 8 min depending on the activator used. RAtchteivaPt2ioYn12oAf PDAPR-dmepaesnkdsetnhte rpehcaeprmtoarco(tlhoigeincaolpiynrhidibiniteios naonfdAtDicPag-drelpoern):dtehnet rtehcreopmtobrisn, bgyenpearsastinedg bthyetmh.e aFcotrivtahtiosrrsesatsroonn,gtlhyeinstearnadcatsrdwVitEhTthaerepirnosteansseit-iavcetivtoattehde rpehceaprmtoarsco(lPoAgRic)altheaffteacrtse opfoawseprifruinl ,trtihgigeenrospfyorridpilnateesl,eat nadctitvicaatgiorne.loAr.ctIinvactoionncloufsiPoAnR, ams alsrkesadthyeppohianrtmedacooulot gbiycaoltihnehribaiutitohnorosf, ADP-dependent receptors, bypassing them For this reason, the standard VET are insensitive to the pharmacological effects of aspirin, thienopyridines, and ticagrelor. No study addressed the separate contribution of fibrin (ogen) and platelets to the clot firmness under DOAC effects, and the use of VET in the setting of DOAC treatment remains limited
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