Efficacy of ex vivo autologous and in vivo platelet transfusion in the reversal of P2Y12 inhibition by clopidogrel, prasugrel, and ticagrelor: the APTITUDE study.

BACKGROUND: Allogenic platelet transfusions (PT) are administered to treat excessive bleeding in patients on P2Y12 receptor inhibitors (RI). We assessed the effect of ex vivo and in vivo PT on platelet activation and aggregation in patients on dual antiplatelet therapy. METHODS AND RESULTS: In the Antagonize P2Y12 Treatment Inhibitors by Transfusion of Platelets in an Urgent or Delayed Timing After Acute Coronary Syndrome or Percutaneous Coronary Intervention Presentation-Acute Coronary Syndrome (APTITUDE-ACS) study, patients presenting with acute coronary syndrome or for elective percutaneous coronary intervention, receiving loading doses of clopidogrel (600 mg, n=13 or 900 mg, n=12), prasugrel 60 mg (n=10), or ticagrelor 180 mg (n=10) were included. PT was performed ex vivo by mixing platelet-rich plasma from blood sampling performed at baseline in increasing proportions with platelet-rich plasma sampled 4 hours after loading dose. The percentage restoration of residual platelet aggregation achieved with 80% proportion PT (residual platelet aggregation 80% PT mix/residual platelet aggregation baseline×100) significantly decreased with increasing potency of P2Y12 RI (83.9±11%, 73±14%, 66.3±15%, 40.9±19% for clopidogrel 600 mg, clopidogrel 900 mg, prasugrel, and ticagrelor, respectively; P for trend <0.0001). In the APTITUDE-Coronary Artery Bypass Graft (APTITUDE-CABG) study, vasodilator-stimulated phosphoprotein-platelet reactivity index, a specific marker of the P2Y12 RI drug-effect, was assessed before and after in vivo PT administered for excessive bleeding in patients undergoing cardiac surgery while on a maintenance dose of aspirin and clopidogrel (n=45), prasugrel (n=6), or ticagrelor (n=3). When compared with baseline, there was a significant relative increase of 23.1% in platelet activation after PT transfusion (42.2±23.6% versus 56.6±18.2%; P=0.0008). CONCLUSIONS: PT restores platelet reactivity in patients with acute coronary syndrome/percutaneous coronary intervention and in patients undergoing cardiac surgery on P2Y12 RI while bleeding with a less effect with increasing potency of P2Y12 inhibition. CLINICAL TRIAL REGISTRATION: URL: http://www.recherche-biomedicale.sante.gouv.fr/pro/comites/coordonnees.htm and http://www.cnil.fr/. Unique identifiers: No. 301111 and No. 1547216v0.

Impact of red blood cell transfusion on platelet aggregation and inflammatory response in anemic coronary and noncoronary patients: the TRANSFUSION-2 study (impact of transfusion of red blood cell on platelet activation and aggregation studied with flow cytometry use and light transmission aggregometry).

OBJECTIVES: This study sought to determine whether red blood cell (RBC) transfusion increases in vivo platelet aggregation and inflammation in coronary and noncoronary patients. BACKGROUND: RBC transfusion increases in vitro platelet activation and aggregation in healthy volunteers, providing a possible explanation for the increase in recurrent ischemic events and mortality reported after RBC transfusion in patients with acute coronary syndromes (ACS). METHODS: Platelet reactivity was measured before and after RBC transfusion in 61 patients (33 with ACS patients and 28 without ACS). Relative changes between baseline and post-transfusion measurements of maximal and residual platelet aggregation were considered with different agonists as well as changes in vasodilator-stimulated phosphoprotein platelet reactivity index and P-selectin expression. Inflammatory and thrombotic biomarkers were also measured before and after transfusion. RESULTS: After RBC transfusion, platelet reactivity was increased when measured using adenosine diphosphate-induced light transmission aggregometry (11.6% relative increase in maximal platelet aggregation, p = 0.004; 10.8% increase in residual platelet aggregation, p = 0.005) and vasodilator-stimulated phosphoprotein platelet reactivity index (20.7% relative increase, p = 0.002), and there was a nonsignificant trend toward an increase in P-selectin expression. Similar results were found with the nonspecific agonist thrombin receptor-activated peptide (relative increases of 11.7% for maximal platelet aggregation, p = 0.04, and 12.7% for residual platelet aggregation, p = 0.02) but not with collagen or arachidonic acid agonists. There were no significant differences in inflammatory and thrombotic biomarkers before and after transfusion. CONCLUSIONS: After RBC transfusion, there is an increase in platelet reactivity, especially with tests measuring the adenosine diphosphate-P2Y12 receptor pathway, without significant variations in inflammatory or thrombotic biomarkers. This in vivo effect may account for the excess of ischemic events observed in the context of patients with ACS treated using percutaneous coronary intervention and P2Y12 inhibitors.

Switching acute coronary syndrome patients from prasugrel to clopidogrel.

OBJECTIVES: This study sought to assess the consequences of switching prasugrel to clopidogrel on platelet inhibition and clinical outcomes after an acute coronary syndrome (ACS). BACKGROUND: Many ACS patients are switched from prasugrel to clopidogrel within the recommended 1-year duration of treatment. METHODS: Platelet reactivity was measured with the VerifyNow P2Y(12) assay (Accumetrics, San Diego, California) in 300 ACS patients treated for 15 days with prasugrel 10 mg. Patients displaying low on-treatment platelet reactivity (LPR) and/or at high risk of bleeding were switched to clopidogrel 75 mg and tested again 15 days later. The rate of patients with high on-treatment platelet reactivity (HPR), P2Y(12) reaction units (PRU) >208, and LPR (PRU <0) were evaluated before and after the switch. Bleeding and ischemic events were also recorded. RESULTS: On a regimen of prasugrel 10 mg, the rate of patients with LPR was 45.6% (n = 137), whereas 4.3% (n = 13) had HPR. A group of 31 patients (10.3%) was switched to clopidogrel 75 mg, of whom 29 had LPR (93.5%) on a regimen of prasugrel. On-treatment platelet reactivity (PRU) increased from 14 ± 4 on a regimen of prasugrel to 155 ±15 on a regimen of clopidogrel (p = 0.0001), resulting in a much lower rate of patients with LPR (9.7%). The rate of patients with HPR increased from 0% with prasugrel to 29% (n = 9) with clopidogrel. The rate of minor bleeding decreased after the switch from 32.2% to 9.7%; p = 0.03. CONCLUSIONS: An LPR is frequent in patients treated with prasugrel 10 mg. Early switching from prasugrel 10 mg to clopidogrel 75 mg reduces the number of patients with LPR and minor bleeding events but unmasks a group of nonresponders to clopidogrel with unknown consequences on clinical outcomes.