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Antithrombotic therapy in atrial fibrillation
1Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA. dsinger@partners.org
Insights
Anticoagulation effectively prevents stroke in atrial fibrillation (AF) patients, though it carries a small bleeding risk. Aspirin is an alternative for lower-risk individuals, but further research is needed for the oldest AF patients.
Area of Science:
- Cardiology
- Neurology
- Geriatrics
Background:
- Atrial fibrillation (AF) affects 10% of individuals over 80.
- AF significantly increases ischemic stroke risk fivefold.
- Anticoagulation is a proven stroke-prevention strategy for AF.
Purpose of the Study:
- To review the efficacy and safety of anticoagulation and aspirin for stroke prevention in AF.
- To identify risk factors for stroke in AF patients.
- To highlight areas for future research in AF stroke prevention.
Main Methods:
- Review of randomized controlled trials on anticoagulation and aspirin in AF.
- Analysis of stroke and hemorrhage risks associated with different treatments.
- Identification of patient subgroups based on stroke risk factors.
Main Results:
- Anticoagulation significantly reduces stroke risk in AF patients with a <0.5% annual intracranial hemorrhage risk.
- Aspirin shows a small stroke-preventive effect.
- Key stroke risk factors include prior stroke, hypertension, diabetes, and older age.
Conclusions:
- Anticoagulation is recommended for high-risk AF patients.
- Aspirin is suitable for lower-risk individuals.
- Further research is crucial for optimizing stroke prevention in the oldest AF patients and improving risk stratification.
Abstract:
Atrial fibrillation is a common condition affecting elderly individuals; as many as 10% of people older than age 80 years have AF. AF is also a potent risk factor for ischemic stroke, raising the risk of stroke fivefold. A set of consistent randomized controlled trials has demonstrated that long-term anticoagulation can largely reverse the risk of stroke attributable to AF. In these trials, anticoagulation generally proved quite safe, raising the risk of intracranial hemorrhage by less than 0.5% per year. The anticoagulation target for AF is INR 2 to 3 with INR 2.5 as the specific goal. The trials were much less consistent about the efficacy of aspirin, although it seems that aspirin has a small stroke-preventive effect. The recommended dose of aspirin is 325 mg per day. Because it raises the risk of hemorrhage and adds the burden of frequent monitoring of INR values, anticoagulation is recommended for those patients with AF at higher risk of stroke. Such higher risk is conferred by the following risk factors: (1) a history of a prior stroke, TIA, or other systemic embolic event; (2) a history of hypertension; (3) diabetes mellitus; (4) left ventricular dysfunction; (5) mitral stenosis; and (6) older age. The exact age threshold conferring sufficiently increased risk is uncertain, with some research indicating the threshold should be age 65 years, and other research indicating the threshold should be age 75 years. For lower-risk patients, aspirin is recommended. Future research should focus on the oldest patients with AF. These individuals face the highest risk of ischemic stroke without anticoagulation and the highest risk of major hemorrhage with anticoagulation. Only small numbers of such elderly patients were included in the randomized trials. Future research should also focus on improved risk stratification, allowing better targeting of anticoagulation. Discoveries of new antithrombotic agents and new drugs and devices for preservation of sinus rhythm could radically improve stroke-preventive strategies for AF.