The Effect of Cessation of 2^nd Generation P₂Y₁₂ Inhibitor Therapy on Platelet Reactivity in Patients One Year After Acute Myocardial Infarction.

objective: To assess the effect of cessation of dual antiplatelet therapy (DAPT) regimens containing 2^nd generation P₂Y₁₂ inhibitors on platelet reactivity, in patients who completed 12 months of DAPT following an acute myocardial infarction (MI).

Background: Clinical data has shown an increased risk for ischemic events in the 90 days following cessation of DAPT. One possible explanation is a “rebound” effect of DAPT cessation on platelet reactivity. Data from patients treated with 2^nd generation P₂Y₁₂ inhibitors is scarce.

Methods: Patients who completed 12 month of DAPT with Prasugrel/Ticagrelor underwent serial assessment of platelet reactivity (on DAPT and 1,4 and 12 weeks post cessation). The primary outcome was platelet reactivity, expressed as platelet reactivity units (PRU) at each time point.

Results: 41 participants were included in this study, (23 Ticagrelor,18 Prasugrel). There was no difference in baseline characteristics between prasugrel/ticagrelor treated patients.

The pattern of platelet reactivity recovery after DAPT cessation differed between the ticagrelor and prasugrel: with ticagrelor, after the initial PRU increase from baseline , the PRU remained stable, while with prasugrel, there was a further increase in PRU between 1 and 4 weeks, with a return to the 1 week level by 12 weeks (p=0.034 for the time*treatment interaction between ticagrelor and prasugrel).

Conclusions: Our results suggest there is a “rebound” effect in platelet reactivity following DAPT cessation with prasugrel, but not ticagrelor. Further research is required to elucidate the pathophysiologic mechanisms behind these findings and to evaluate potential strategies to prevent or overcome this “rebound” effect.