Despite being the most at risk, older people are the least likely to receive preventive treatment for stroke. None of the available stroke risk stratification schemes performed particularly well in older people, a recent study reveals.
Researchers compared the performance of the commonly used stroke risk stratification schemes in a contemporary population of older people. It covered 665 patients aged 75 or over with atrial fibrillation.
AdvertisementAtrial fibrillation is the most common form of irregular heartbeat. It is caused due to an abnormal heart rhythm and is associated with stroke and heart failure. Atrial fibrillation risk increases with age. The prevalence is highest in people aged 85 and over. Deadly outcomes such as stroke are more common in older patients. A stroke results when the blood supply to any part of the brain gets interrupted. People with atrial fibrillation have irregularly beating heart chambers. This results in dislodging blood clots, which travel to the brain and cause strokes.
A number of risk stratification schemes exist so as to assess a person's risk of stroke (CHADS2, revised CHADS2, NICE, ACC/AHA/ESC etc.). The CHADS2 index is the simplest one. CHADS2 is an acronym for Congestive heart failure, Hypertension, Age 75 and older, Diabetes and previous Stroke. Risk stratification schemes compute 'stroke risk scores'. CHADS2, for example, awards a score ranging from 0 to 6. Each risk factor is given points. Previous stroke adds two points to the score. Based on the score, most of the people are stratified into risk categories (low, moderate, high) by most of the risk stratification schemes.
Identifying people with 'high risk' is important since management of the disease is different for them. International guidelines recommend that all patients assessed as high risk are offered warfarin, a drug that prevents blood clot formation. Warfarin belongs to a group of drugs called vitamin K antagonists, since it reduces blood clotting by inhibiting vitamin K. The Birmingham Atrial Fibrillation Treatment of the Aged (BAFTA) trial showed that among elderly patients with atrial fibrillation (AF), anticoagulation with warfarin was superior to aspirin for primary stroke prevention. Dagibatran, rivaroxaban and apixiban are other new drugs found to have superior efficacy.
Though guidelines insist that high-risk atrial fibrillation patients are offered vitamin K antagonists in most circumstances, these drugs remain underused for stroke prevention. Underuse is more marked in the older population. Better prevention of stroke in older patients with atrial fibrillation is therefore a priority.
Researchers concluded that all the schemes studied had a similar limited ability to predict the risk of stroke. The deleterious effects would shed a worse impact on the older population who are at a greater chance to suffer atrial fibrillation and hence stroke.
Based on the study, authors recommend that clinicians classify all patients over 75 as high risk and offer oral anticoagulation for these patients until better tools are available. This would seem more practical than relying on the 'potentially less effective' risk analysis techniques.
Source: Performance of stroke risk scores in older people with atrial fibrillation not taking warfarin: comparative cohort study from BAFTA trial; FDR Hobbs et al; BMJ 2011; 342: d3653