Impaired response to antiplatelet therapy with acetylsalicylic acid (ASA) and clopidogrel (CLO) has been associated with an increased risk of stent thrombosis and ischemic events after coronary stent implantation. We sought to investigate whether patients with a low response (LR) to ASA or CLO are at increased risk for periprocedural and short-term ischemic events after coronary stent implantation.

A total of 219 patients pretreated with ASA and CLO underwent percutaneous coronary intervention (PCI) with stent implantation. Whole blood impedance platelet aggregometry was performed with the Multiplate analyzer (Dynabyte, Munich, Germany) to test the response to ASA (ASPI test) and CLO (ADP test) within 12 to 18 hours after PCI. Patients were classified as ASA-LR, CLO-LR, dual LR, and controls. Study end points included myocardial infarction, stent thrombosis, and death assessed during the periprocedural period and at 30 days.

Acetylsalicylic acid–LR was present in 34 (16%), CLO-LR in 33 (15%), and dual LR in 19 (9%) patients. Percutaneous coronary intervention–related myocardial infarction was encountered in 19 (9%) patients, with the highest incidence in dual-LR group (26.3%, P = .039). Composite ischemic events at 30 days were significantly more frequent in the dual-LR group than in other groups (36.8% vs 8.8% ASA-LR vs 6.1% CLO-LR vs 6.8% controls, P < .001). In multivariable analysis, dual LR (odds ratio 7.35, 95% CI 2.21-24.42, P < .001) and multivessel PCI (odds ratio 4.56, 95% CI 1.33-15.62, P = .016) were independently associated with ischemic events at 30 days.

Dual LR to ASA and CLO is associated with an increased risk for short-term ischemic events after coronary stent implantation.