Clopidogrel discontinuation after myocardial infarction and risk of thrombosis: a nationwide cohort study

The benefit of extending clopidogrel treatment beyond the 12-month period recommended in current guidelines after myocardial infarction (MI) is debated. We analysed the risk of adverse cardiovascular outcomes after discontinuation of 12 months of clopidogrel treatment. This Danish retrospective nationwide study included all patients treated with clopidogrel after discharge from a first-time MI during 200409. The risk of death or recurrent MI after the discontinuation of clopidogrel was studied by multivariable Poisson regression models. Patients treated with and without percutaneous coronary intervention (PCI) were analysed separately. The follow-up was 18 months. Of the 29 268 patients included, 3214 (11.0) experienced death or recurrent MI. There were 9819 (33.6) patients treated only medically and 19 449 (66.4) patients treated with PCI. Twelve months after the index MI, for patients treated only medically, the risk of death or recurrent MI in the first 90-day period of clopidogrel discontinuation was 1.07 (0.651.76; P 0.79) [adjusted incidence rate ratio (IRR) and 95 confidence interval] compared with the next 90-day period of discontinuation. For patients treated with PCI, the corresponding IRR was 1.59 (1.112.30; P 0.013). The risk of recurrent MI yielded an IRR of 0.77 (0.361.67; P 0.51) for patients treated only medically and 1.87 (1.113.15; P 0.019) for PCI-treated patients. Discontinuation of clopidogrel 12 months after MI is associated with an increased risk of death or recurrent MI in the first 90 days of discontinuation compared with the next 90-day period of discontinuation for patients treated with PCI, but not for patients not treated with PCI.