Single and dual antiplatelet therapy in elderly patients of medically managed myocardial infarction

Backgrounds: To examine the comparative effectiveness between dual and single antiplatelet therapies in real-world, medically managed elderly patients with acute myocardial infarction (AMI). Methods: This retrospective study identified very elderly (> 85 years) patients, who were medically managed, with their first AMI from the Taiwan National Health Insurance claims database from 2007 to 2010. Patients were classified as dual antiplatelet therapy (DAPT) group, aspirin only group and clopidogrel only group. Study outcomes included all-cause death, cardiovascular death and gastrointestinal bleeding. Treating DAPT group as the reference, we employed a multivariable Cox regression model to compare the relative risks of outcomes between 3 groups using pairwise comparison approach. Results: Among 1469 patients with incident ST-elevation myocardial infarction (STEMI, 14%) or non-STEMI (86%), 390 patients were prescribed DAPT, 549 aspirin only, and 530 clopidogrel only. After 9 months of follow-up, aspirin only group had similar risks of all-cause death (adjusted HR 1.21, 95% CI 0.77-1.89, p = 0.41), cardiovascular death (adjusted HR 1.16, 95% CI 0.66-2.04, p = 0.60) and gastrointestinal bleeding (adjusted HR 1.66, 95% CI 0.77-3.57, p = 0.20) in comparison with DAPT group. Clopidogrel users had a higher risk of all-cause death (adjusted HR 1.50, 95% CI 1.00-2.25, p = 0.049) but similar risks of cardiovascular death and gastrointestinal bleeding when compared with DAPT. Conclusions: Among very elderly patients who were medically managed after AMI, single antiplatelet therapy had comparable protective effect as DAPT. But clopidogrel only strategy was associated with a higher risk of all-cause death.