Impact of Clopidogrel Dose Adjustment According to Platelet Reactivity Monitoring in Patients With High on Treatment Platelet Reactivity Undergoing Percutaneous Coronary Intervention

Acute coronary syndromes are related to the development of a platelet derived thrombus on a ruptured coronary atheroma. Use of dual antiplatelet therapy aspirin-thienopyridine a significantly reduced the risk of major adverse cardiovascular events (MACE) after percutaneous coronary intervention (PCI). However despite these therapeutic innovations, the rate of MACE in patients treated using PCI and particularly in those suffering of an acute coronary syndrome is around 5% in randomized trials. Within the factors associated with MACE, high on treatment platelet reactivity following clopidogrel loading dose has been identified as a key factor. In fact it is widely recognized that there is a large inter individual variability in clopidogrel responsiveness. In addition several authors have demonstrated a strong link between high on treatment platelet reactivity following clopidogrel loading dose and the occurrence of post PCI MACE. Vasodilator Phosphoprotein index measurement (VASP index) enables a reproducible, standardized and specific assessment of clopidogrel responsiveness.

The investigators previous works have demonstrated that a VASP index ≥ 50% had a high negative predictive value for post PCI MACE in patients undergoing PCI and that tailored clopidogrel loading dose in order to obtain a VASP index < 50% before PCI resulted in a reduction in the rate of post PCI MACE.

Prasugrel is a new generation thienopyridine with a faster and more powerful anti platelet effect compared to clopidogrel. It was shown to be superior to clopidogrel to reduce post PCI MACE in acute coronary syndromes. However in this randomized trial prasugrel achieved an excessive blockade of platelet reactivity responsible for a significant increase in bleeding events in some patients and an insufficient blockade in up to 325% of the remaining patients.

Therefore the investigators hypothesized that a strategy of individually tailored loading and maintenance dose of clopidogrel may be superior to prasugrel standard therapy in achieving an optimal platelet reactivity inhibition in acute coronary syndrome patients undergoing PCI.