Anticoagulation therapy for cardioembolic stroke prevention in the elderly: Defining benefits and risks

The number of elderly patients aged 65 years and over has increased over the last 100 years owing to improvements in antisepsis, clean water/sanitation and preventive health strategies. As a result, more people are living longer than in the past and more people require healthcare at an older age. Atrial fibrillation increases with advancing age and is an independent risk factor for cardioembolic stroke. Warfarin anticoagulation has proven to be superior to antiplatelet agents in reducing stroke in high-risk atrial fibrillation patients in several trials. However, owing to potentially harmful or fatal bleeding risks, namely gastrointestinal and intracranial hemorrhage, anticoagulation remains underutilized even in patients in whom the benefit outweighs the risk. The incidence of intracranial hemorrhage during carefully managed warfarin anticoagulation is approximately 0.4-1% annually, but is higher in patients older than 85 years of age, and in patients with supratherapeutic levels of anticoagulation (i.e., international normalized ratio >3.5), whereas gastrointestinal bleeding occurs in approximately 2.5% of patients. Many atrial fibrillation patients aged 75 years or older have an annual ischemic stroke risk between 4 and 18% but remain untreated owing to exaggerated fear of hemorrhagic events, despite a clear benefit-to-risk ratio. We review the literature regarding the assessment of cardioembolic ischemic stroke risk in the aging population and relative benefits of warfarin anticoagulation compared with aspirin therapy, as well as the recent trial comparing warfarin against dabigatran, and relative hemorrhagic risks. We review recent literature providing recommendations about improving outpatient anticoagulation therapy and newer MRI data detecting asymptomatic cerebral microbleeds, which may be clues to why some patients have intracranial bleeding during anticoagulation therapy.