Platelet aspirin resistance in ED patients with suspected acute coronary syndrome

The Future of Aspirin Therapy in Cardiovascular Disease

Much has been written about the demise of aspirin (ASA) but reports of its death are premature. The drug remains one of the most widely prescribed by physicians worldwide. It is cheap, familiar, and effective for a variety of uses, including in patients with acute or prior myocardial infarction, ischemic stroke, peripheral artery disease, and percutaneous or surgical revascularization procedures, as well as for use for pain and fever relief. Beyond physician prescription or recommendation, over the counter use of ASA is common, including for primary cardiovascular prevention, though this decision really should involve a discussion of risks and benefits with a physician. ASA is an essential member of the duo that makes up dual antiplatelet therapy (a P2Y₁₂ inhibitor plus ASA) and also dual pathway inhibition (vascular dose rivaroxaban plus ASA), and data for both approaches are growing. Furthermore, research is ongoing as to the optimal dosing frequency (once vs twice daily), potentially safer gastrointestinal delivery, and possibly more effective formulations in terms of platelet inhibition. One goal of ASA research is to try to reduce bleeding complications that are a risk with all anti-thrombotic therapies. Although its exact roles will continue to evolve, the future for ASA remains bright.

Aspirin insensitive thrombophilia: transcript profiling of blood identifies platelet abnormalities and HLA restriction

Aspirin is the most widely used antiplatelet agent because it is safe, efficient, and inexpensive. However, a significant subset of patients does not exhibit a full inhibition of platelet aggregation, termed 'aspirin resistance' (AR). Several major studies have observed that AR patients have a 4-fold increased risk of myocardial infarction (MI), stroke, and other thrombotic events. Arachidonic acid-stimulated whole blood aggregation was tested in 132 adults at risk for ischemic events, and identified an inadequate response to aspirin therapy in 9 patients (6.8%). Expression profiling of blood RNA by microarray was used to generate new hypotheses about the etiology of AR. Among the differentially expressed genes, there were decreases in several known platelet transcripts, including clusterin (CLU), glycoproteins IIb/IIIa (ITGA2B/3), lipocalin (LCN2), lactoferrin (LTF), and the thrombopoetin receptor (MPL), but with increased mRNA for the T-cell Th1 chemokine CXCL10. There was a strong association of AR with expression of HLA-DRB4 and HLA-DQA1. Similar HLA changes have been linked to autoimmune disorders, particularly antiphospholipid syndrome (APS), in which autoantibodies to phospholipid/protein complexes can trigger platelet activation. Consistent with APS, AR patients exhibited a 30% reduction in platelet counts. Follow-up testing for autoimmune antibodies observed only borderline titers in AR patients. Overall, these results suggest that AR may be related to changes in platelet gene expression creating a hyperreactive platelet, despite antiplatelet therapy. Future studies will focus on determining the protein levels of these differential transcripts in platelets, and the possible involvement of HLA restriction as a contributing factor.