Patients at high risk of thrombotic events after
percutaneous coronary intervention (PCI) may potentially benefit from intensified antiplatelet
therapy. However, more potent antiplatelet
therapy would be expected to only overcome risk that is mediated by high platelet reactivity (PR). We used mediation analysis to determine the contribution of residual PR to the 2-year risk of
major adverse cardiac events (
MACE; the composite of
cardiac death,
myocardial infarction, or
stent thrombosis) associated with clinical risk factors after PCI with
drug-eluting stents (DES) in 8,374 patients from the prospective, multicenter Assessment of Dual AntiPlatelet
Therapy with
Drug-Eluting Stents (ADAPT-DES) registry. Residual PR on
clopidogrel, as measured by the VerifyNow P2Y12 point-of-care assay, was included as a continuous linear mediator variable in Cox proportional hazards regression. Among 7 factors independently associated with 2-year
MACE, residual PR partly mediated the effect of diabetes (13.4% attributable risk),
anemia (22.9% attributable risk), and
acute coronary syndromes (7.3% attributable risk). A PR-mediated effect inversely affected the
MACE risk associated with smoking (10.4% attributable risk). The increased ischemic risk of
chronic kidney disease, multivessel disease, and previous
myocardial infarction were not mediated by residual PR. In conclusion, high residual PR mediates little or none of the increased 2-year
MACE risk associated with baseline risk factors in patients treated with
clopidogrel after successful PCI with DES. Intensifying antiplatelet
therapy is therefore unlikely to substantially mitigate the excess ischemic risk from these variables.