The use of antiplatelet therapy in cardiovascular prophylaxis has always been a two-edged sword: on the one hand it inhibits arterial thrombosis and on the other promotes bleeding – a classic pharmacological lesson in benefit versus risk. The more effective the antiplatelet therapy the greater the cardioprotection, but at the same time the higher the propensity for serious bleeding. Thus, dual antiplatelet therapy (DAPT) may be indicated where the ischaemic risk is particularly high and the bleeding risk is normal / low, but contraindicated in other circumstances. Much evidence now supports DAPT use in patients post-acute coronary syndrome, for up to one year, but what has been unclear is whether longer term DAPT is useful, neutral or dangerous. The latest contribution to this debate is provided by the paper by Bonana M. et al. (New Engl J Med 2015;372:1791-1800), who randomly assigned 21,162 patients who had had a myocardial infarction 1 to 3 years earlier to receive (in addition to aspirin) placebo or ticagrelor, the latter at two different doses: 60 mg or 90 mg twice daily. As compared with placebo, either dose of ticagrelor was associated with a 15% decrease in the rate of the primary end point of death from cardiovascular causes, myocardial infarction, or stroke. However, ticagrelor treatment also increased clinically significant bleeding complications by a factor of 2.3 to 2.7 and transfusions by a factor of 3.1 to 3.8. On this basis, the risks and benefits seem to balance each other almost exactly, suggesting that guidelines are unlikely to change as a result of this study, and will continue to suggest 1 year of DAPT as routine post-ACS, unless patients are at particularly high risk for ischemic events (e.g., diabetes, renal disease, multivessel disease, recurrent myocardial infarction).
Dual antiplatelet therapy: A two-edged sword?
Prof Albert Ferro
Professor of Cardiovascular Clinical Pharmacology, Faculty of Life Sciences & Medicine (Cardiovascular Division), King's College London. Lead on Clinical Pharmacology teaching, King's College London. Honorary Consultant Physician, Guy's and St Thomas' Hospitals. Chair, Guy's and St Thomas' Drug & Therapeutics Committee. Reviews Editor, British Journal of Clinical Pharmacology.