Δοκιμασίες λειτουργικότητας αιμοπεταλίων και PCI Εμμανουήλ Βαβουρανάκης

Transcription

1 Δοκιμασίες λειτουργικότητας αιμοπεταλίων και PCI Εμμανουήλ Βαβουρανάκης Αναπλ. Καθηγητής Καρδιολογίας Ιπποκράτειο ΓΝΑ

2 Haematology Research Laboratory!! Platelets Small anucleate discoid cells Involved in primary haemostasis: " " platelet plug formation occurs at sites of injury within seconds important in stopping blood loss from capillaries, small arterioles, and venules! Internal structure and membrane play central role

3 Haematology Research Laboratory!!! Platelet reactions in haemostasis Adhesion: platelets come into contact with endothelium (blood vessel injury) Shape change: platelets become spherical and extend pseudopodia Secretion: contents of platelet granules released (e.g. ADP, fibrinogen, etc)!! Aggregation: platelets aggregate via specialised receptors Procoagulant activity: negatively charged phospholipid translocated to outer surface of the platelet membrane and involved in coagulation cascade

4 Receptors Involved in Platelet Activation and Aggregation and Binding Sites of Platelet Inhibitors Binding Sites of Platelet Inhibitors at the P2Y12 Receptor JACC Cardiovasc Interv Nov;6(11):

5 PLATELET FUNCTION TESTS Different platelet function tests have been developed, based on the assessment of platelet adhesion and aggregation, on the activation of platelets under high shear conditions, on the analysis of physical properties of the thrombus, on the measurement of platelet compounds

6 Haematology Research Laboratory!!! Assessment of platelet function and activation Platelet count and morphology Bleeding time historical Light transmission aggregometry gold standard! Rapid, point-of-care assays

7 The oldest available method evaluating platelet function. It is still considered as the gold standard to assess both aspirin and clopidogrel response, despite a lack of standarisation. It evaluates luminosity using an optical aggregometer with a fixed wavelength spectrophotometer as aggregation occurs in platelet-rich plasma (PRP) under stirring conditions following stimulation with a platelet agonist

8 Haematology Research Laboratory!! Light transmission aggregometry Measures increase in light transmission through a platelet suspension when platelets are aggregated by an agonist Many variables may affect the results! Accuracy and reproducibility of technique poor! Difficult to interpret results in cases of low platelet count

9 Haematology Research Laboratory Typical aggregation tracing

10 It assesses platelet aggregation in anticoagulated whole blood under high shear forces (5,000 6,000/seconds). It records the closure time (CT) of a 150 μm aperture collagen coated membrane.

11 PFA The use of two different cartridges allows to differentiate intrinsic or severe platelet function abnormalities Prolonged times of C/ADP cartridge alone or with C/EPI cartridge,von Willebrand Disease, Bernard Soulier syndrome, or Glanzmann s thromboasthenia from those due to aspirin treatment (prolonged time of C/EPI cartridge).

12 The test is very sensitive to Mild abnormalities of platelet function as well as to many other variables including platelet count, red blood cells, and haematocrit In patients undergoing different kinds of elective surgery, the PFA-100 may serve a useful pointof-care tool for guiding blood transfusion management (36), particularly in cardiac surgery (37, 38)

13

14 Haematology Research Laboratory Whole blood flow cytometry of platelets Blood Anticoagulant (usually buffered Na Citrate) Dilution Monoclonal antibody/isotype control (labelled with fluorophore) Add agonist Fixation Dilution Analysis

15

16 Haematology Research Laboratory Flow cytometric markers of platelet activation! Platelet vasodilator stimulated phosphoprotein (VASP): " intracellular signalling molecule which is nonphosphorylated at basal state and phosphorylated in PGE1 inhibited platelets " commercial assay available which measures VASP phosphorylation in the presence of PGE1 " clopidogrel responsiveness can be demonstrated by the persistence of VASP phosphorylation induced by PGE1 with simultaneous addition of agonist, ADP

17 Haematology Research Laboratory VASP + PGE1 + PGE1 + ADP ADP Clopidogrel

18

19 VerifyNow P2Y12 assay The agonists used include arachidonic acid (AA) for the aspirin assay, A combination of adenosine diphosphate (ADP) and prostaglandin E1 for the P2Y12 receptor assay A thrombin receptor activating peptide for the glycoprotein IIb/IIIa assay (39, 40). Results are expressed as P2Y12 reaction units (PRU), with higher values reflecting higher platelet reactivity

20

21

22

23

24

25

26 Comparison of three PFTs (LTA, VASP, and VerifyNow) Clopidogrel non responsiveness to be 13%, 39%, and 33%, LTA, VASP, and VerifyNow Poor agreement between assays although P2Y12 receptorspecific tests VASP and VerifyNow P2Y12 assay appear to correlate well.

27 Platelet reactivity and Clopidogrel Tantry et al. JACC 2013

28

29 Clopidogrel Treatment Failure Polymorphism in the gene encoding the cytochrome P450 (CYP) 2C19 enzyme Responsible for converting the pro-drug into its active metabolites.

30 Identifying clopidogrel treatment failure based on CYP genotyping Routinely is not recommended Variation in CYP genotype accounts for only about 10% of individual variability in response to the drug. Its sensitivity and specificity for screening purposes and modification of clinical care requires further evaluation. Whether a combination of platelet function and genetic testing may be superior to either method alone is currently being investigated

31

32

33

34 On Treatment reactivity and clinical events.. Stent thrombosis

35 On Treatment reactivity and clinical events.. Post PCI events

36

37 Randomized trials GRAVITAS trial ARCTIC trial TRIGGER PCI trial

38

39

40

41

42

43

44

45

46

47 TRIGGER-PCI study JACC Vol. 59, No. 24, 2012

48 Successful PCI with DES without major complication and NO GPIIb/IIIa use N ~6500 Post-PCI VerifyNow P2Y12 Assay (PRU) 2-7 hours after MD of clopidogrel 75 mg at day 1 post-pci Non-Responder Yes PRU > 208 No Responder A N = 1075 Prasugrel arm Prasugrel LD 60 mg Prasugrel MD 10 mg QD + Clopidogrel placebo B N = 1075 Clopidogrel arm Placebo LD Clopidogrel MD 75 mg QD + Prasugrel placebo C N = 4350 Standard Therapy Clopidogrel MD 75 mg QD N = 2,150 33% Non-interventional study (Registry) Clinical Follow-up and blinded VerifyNow Assessment at 90 days, 180 days Primary Endpoint: 6 month CV Death or MI

49 JACC Vol. 59, No. 24, 2012

50 Vavuranakis et al. Circulation J. 2011;75(9):

51 Vavuranakis et al. Circulation J. 2011;75(9):

52 Vavuranakis et al. Circulation J. 2011;75(9):

53 Among STEMI patients undergoing primary PCI, those with initial PRU levels above the cutoff point of 251.5, have higher incidence of major adverse cardiac events during long term follow up. Vavuranakis et al. Int J Cardiol Oct 20;176(3):

54 Platelet reactivity and newer antiplatelet agents

55

56 14 studies and 1822 patients included

57