Abstract 10390: Prasugrel Treatment is More Effective in Reducing Platelet Reactivity in PCI Patients with Low Clopidogrel Response Compared to Dose Increase of Clopidogrel

A dual anti-platelet therapy is a routine procedure after PCI. A low response to thienopyridine treatment (LR) as determined by platelet function testing has been shown to be associated with a significantly increased risk for stent thrombosis and other ischemic events. In order to intensify the anti-platelet regimen patients can either be reloaded with clopidogrel with the subsequent increase of its daily dose to 150 mg/d or the treatment can be switched to prasugrel. Few studies are available so far which compare the efficacy of these treatments in patients with a LR to clopidogrel. Methods: Platelet function testing using multiple electrode aggregometry (Multiplate analyzer) was performed in 1028 patients undergoing PCI. Patients with low response to initial clopidogrel loading dose (600mg) and treatment (75mg) were either reloaded with 600 mg clopidogrel and then treated with daily 150mg clopidogrel (Group I, n=64) or were immediately switched to prasugrel loading dose (60mg) and standard daily therapy (10mg) (Group II, n=40). We retrospectively analysed the platelet function in both groups. Aggregation was tested one the first day after PCI in hirudin blood after stimulation of platelets with 6.4 µM ADP and expressed in Units (U). Prospectively a cut-off point > 42U was defined as LR, Results: In group I aggregation was 56±18 U (mean ± sd) before vs 39±19 U after reloading and therapy modification. 22 patients (34%) still showed a LR, while only 4 (6%) fulfilled the criteria of a HR to clopidogrel. In group II aggregation was 64±18 U before vs 29±17 U after switching to prasugrel. 6 patients showed a LR under prasugrel treatment (15%). 13 patients showed a HR to prasugrel treatment (32%). Conclusions: Prasugrel is significantly more effective in achieving sufficient platelet inhibition in low responders to the standard clopidogrel-dose compared to a dose increase of clopidogrel dose (reduction of the average aggregation by 54% vs. 31% for clopidogrel). The effect is achieved at the cost of an increased higher response rate which has been shown to be associated with more major bleeding.