Selective and rapid monitoring of dual platelet inhibition by aspirin and P2Y(12) antagonists by using multiple electrode aggregometry

Background: Poor platelet inhibition by aspirin or clopidogrel has been associated with adverse outcomes in patients with cardiovascular diseases. A reliable and facile assay to measure platelet inhibition after treatment with aspirin and a P2Y(12) antagonist is lacking. Multiple electrode aggregometry (MEA), which is being increasingly used in clinical studies, is sensitive to platelet inhibition by aspirin and clopidogrel, but a critical evaluation of MEA monitoring of dual antiplatelet therapy with aspirin and P2Y(12) antagonists is missing. Design and Methods: By performing in vitro and ex vivo experiments, we evaluated in healthy subjects the feasibility of using MEA to monitor platelet inhibition of P2Y(12) antagonists (clopidogrel in vivo, cangrelor in vitro) and aspirin (100 mg per day in vivo, and 1 mM or 5.4 mM in vitro) alone, and in combination. Statistical analyses were performed by the Mann-Whitney rank sum test, student' t-test, analysis of variance followed by the Holm-Sidak test, where appropriate. Results: ADP-induced platelet aggregation in hirudin-anticoagulated blood was inhibited by 99.3 +/- 1.4% by in vitro addition of cangrelor (100 nM; p < 0.001) and by 64 +/- 35% by oral clopidogrel (600 mg) intake (p < 0.05; values are means +/- SD). Pre-incubation of blood with aspirin (1 mM) or oral aspirin intake (100 mg/day for 1 week) inhibited arachidonic acid (AA)-stimulated aggregation > 95% and 100 +/- 3.2%, respectively (p < 0.01). Aspirin did not influence ADP-induced platelet aggregation, either in vitro or ex vivo. Oral intake of clopidogrel did not significantly reduce AAinduced aggregation, but P2Y(12) blockade by cangrelor (100 nM) in vitro diminished AA-stimulated aggregation by 53 +/- 26% (p < 0.01). A feasibility study in healthy volunteers showed that dual anti-platelet drug intake (aspirin and clopidogrel) could be selectively monitored by MEA. Conclusions: Selective platelet inhibition by aspirin and P2Y(12) antagonists alone and in combination can be rapidly measured by MEA. We suggest that dual anti-platelet therapy with these two types of anti-platelet drugs can be optimized individually by measuring platelet responsiveness to ADP and AA with MEA before and after drug intake.