Risks and benefits of antiplatelet therapy in patients with abdominal aortic aneurysm without symptomatic atherosclerotic disease: a nationwide cohort study

Abstract

Abstract Background Patients with abdominal aortic aneurysm (AAA) suffer a high risk of ischemic events associated with concomitant atherosclerotic cardiovascular disease, and current clinical practice guidelines recommend antiplatelet therapies to mitigate this risk. However, in patients with AAA and no symptomatic atherosclerosis, the benefit of antiplatelet is sparsely investigated. Purpose To assess the effectiveness of antiplatelets vs no antiplatelets on the risk of ischemic events (composite of myocardial infarction and ischemic stroke) and bleeding in individuals with AAA who had no concomitant atherosclerotic vascular disease. Methods We designed a target trial to compare outcomes among treatment initiators and non-initiators and emulated the trial contingent on patient eligibility at time of inclusion, utilizing Danish nationwide observational data from January 2010 through August 2021. Confounding was handled by means of inverse probability treatment weighting based on the propensity score. The emulated sequential trial results for all possible trial months were pooled by means of pooled logistic regression models to estimate the intention-to-treat average treatment effects, and the 5-year associated treatment differences were expressed as hazard ratio (HR) with 95% confidence intervals (CI) and estimated event-free survival. Results A total of 6,344 patients provided 131,047 trial participants: 3,363 of these were new initiators of antiplatelet therapy, while 127,684 were non-initiators. During a median follow-up of 24 months, 173 and 369 ischemic events occurred among initiators and non-initiators, respectively. The corresponding HR of 0.91 (CI 95% 0.73 to 1.17) and an estimated absolute event-free survival difference of -0.6% (Figure 1). For bleeding, the HR was 1.26 (CI 0.97 to 1.58) and the event-free survival difference was 1.0%. Conclusion This target trial emulation, using nationwide observational data on all patients with AAA and no record of symptomatic atherosclerotic disease, did not find evidence of antiplatelets to lower the risk of ischemic events, but also no evidence of substantial higher bleeding risk. The observed differences between the treatment groups were minimal, suggesting limited clinically relevance of this treatment.ischemia- and bleeding free survival