Variability in Platelet Reactivity among STEMI patients treated with Prasugrel versus Ticagrelor

Introduction: Dual antiplatelet therapy (DAPT) consisting of the combination of aspirin and a P₂Y₁₂ receptor inhibitor is the cornerstone of the treatment protocol in STEMI patients. Recently, the ISAR-REACT 5 trial suggested better outcomes in patients who received Prasugrel in comparison with Ticagrelor. Consequently, the current guidelines were adjusted to favor Prasugrel, though the cause for the observed advantages of Prasugrel was not sufficiently delineated.
Objectives: The current study aims to compare the effectiveness of platelet inhibition(PA) in STEMI patients treated with either Prasugrel or Ticagrelor.
Methods: A prospective study comprising 598 consecutive STEMI patients who were hospitalized in an ICCU at Sheba medical center, and underwent PPCI with subsequent platelet aggregation assay obtained on the 3rd day of hospitalization. Of them,188 were treated with clopidogrel and were excluded. Patients older than 75 years were also excluded. Assessment of the PA was performed using both an ADP and arachidonic acid(AA) aggregation assays.
Results: Of 346 patients, 183 were treated with Ticagrelor compared with 163 treated with Prasugrel. Although both medications are considered reasonable within the ≤ 75 years age group, patients treated with Prasugrel were younger (56.9 ±9 vs 60.8 ±8,p <0.01). No differences were observed pertaining to infarct size or area. In terms of LV function, we did not observed differences in the LVEF on echocardiography nor in the number of culprit coronary arteries on angiography. Similar effectiveness of ADP-based platelet inhibition was found for both agents (Ticagrelor 29 [20-39] vs Prasugerl 27 [21-35], p =0.46). Conversely, Prasugrel was shown to be more efficacious in inhibiting AA platelet activity (13 [7-20] vs 16 [10-24], p <0.01). No differences in all-cause 1-year mortality or in-hospital complications were found.
Conclusions: Real-Life experience among STEMI patients shows that while Prasugrel was equivalent to Ticagrelor in the context of ADP-based platelet inhibition, Prasugrel was superior in AA-based inhibition, suggesting a more comprehensive platelet inhibition which could account for the observed advantages described in the recent trials.