Title: Clinical Relevance of Clopidogrel Unresponsiveness During Elective Coronary Stenting: Experience With the Point-of-Care Platelet Function Assay-100 C/ADP
Topic: Interventional Cardiology
Date Posted: 4/21/2010
Author(s): Moerenhout CM, Claeys MJ, Haine S, et al.
Citation: Am Heart J 2010;159:434-438.
Clinical Trial: No
Study Question: What is the clinical impact of unresponsiveness to clopidogrel in patients undergoing elective coronary artery stenting?
Methods: The authors evaluated the association between preprocedural platelet inhibition and postprocedural myonecrosis in 250 patients undergoing elective percutaneous coronary intervention (PCI). Platelet aggregation testing was performed at the time of the intervention using a point-of-care assay, the Platelet Function Assay (PFA-100C/ADP; Dade-Behring, Deerfield, IL). Nonresponse to clopidogrel was defined as a PFA closure time of <71 seconds under dual oral antiplatelet therapy. Postprocedural myonecrosis was defined as an elevation in creatine kinase-MB >1x the upper limit of normal 12-24 hours after intervention. The secondary endpoint was a composite endpoint of major adverse cardiac events (MACE) including death, myocardial infarction, and stent thrombosis at 6 months.
Results: Preprocedural PFA closure time was determined in 242 patients and ranged from 31 to 300 seconds, with a mean value of 147 seconds. Seventeen (7%) patients were nonresponders. Post-PCI myonecrosis occurred in 29 patients (12%) and was more common in nonresponders than in normal responders (29% vs. 11%, p = 0.04). This difference remained significant after adjusting for baseline differences. MACE at 6 months occurred in 13 patients and was comprised of one sudden death possibly related to stent thrombosis and 12 post-PCI myocardial infarctions. MACE was nonsignificantly more common in the nonresponder group (12% vs. 5%, respectively; p = 0.2).
Conclusions: The investigators concluded that unresponsiveness to clopidogrel as assessed by PFA-100C/ADP is an independent risk factor for thrombotic complications after coronary intervention.
Perspective: This small underpowered study suggests that patients who are poorly responsive to clopidogrel are more likely to have myonecrosis after elective PCI. While the study did not find a significant difference in postprocedural MI, this was probably related to the small study size. Larger studies are needed to confirm these findings and to assess the utility of using either prasugrel or larger doses of clopidogrel in patients who are nonresponders to clopidogrel. Hitinder S. Gurm, M.B.B.S., F.A.C.C.
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