Impact of initial clinical presentation on clopidogrel low response.

Background: Large interindividual variability exists in clopidogrel response. Clopidogrel low response correlates with poor prognosis after percutaneous coronary intervention. Some authors also suggest intraindividual variability over time.

Aim: To assess the impact of initial clinical presentation on clopidogrel low response.

Methods: In this prospective study, clopidogrel response was assessed in 100 patients. Fifty patients presenting with acute coronary syndromes (ACS group) were compared with 50 patients with stable coronary artery disease matched 1:1 for age, sex, body mass index and diabetes (stable group). All patients were tested 18-24h after a 600 mg loading dose of clopidogrel using the VerifyNow-P2Y12 test (results expressed as platelet reaction units [PRUs]). Patients under chronic clopidogrel therapy or treated with glycoprotein IIb/IIIa inhibitors, bivalirudin or thrombolytics were excluded.

Results: Mean age was 61 ± 12 years in each group; 28% of patients in each group were diabetic; mean body mass index was 27.6 ± 5.6 kg/m(2) in the ACS group and 27.9 ± 5.9 kg/m(2) in the stable group (p=0.80). Mean PRU values were 197 ± 81 in the ACS group and 159 ± 94 in the stable group (p=0.03). By multivariable analysis, the ACS group was significantly associated with a higher PRU value (p=0.02). There were significantly more clopidogrel low responders (PRU value>230) in the ACS group (38% vs. 18%; p=0.04).

Conclusion: Our study confirms that initial clinical presentation, especially ACS, is a strong predictor of clopidogrel low response; this suggests that the evolution of coronary artery disease for one patient influences the clopidogrel response over time. These results are in accordance with recent trials showing a benefit for more aggressive antiplatelet therapy in ACS patients.