Stroke risk in an elderly population with atrial fibrillation

Abstract

Patients with nonvalvular atrial fibrillation (AF) have an increased risk of stroke, but the absolute rate of stroke varies widely depending on coexistent vascular disease. We assessed the stroke rate and predictive value of two published schemes for stroke risk stratification in a population-derived cohort of 259 elderly people with nonvalvular AF followed for a median of 5.3 years. The rate of ischemic stroke was 2.8% per year (95% confidence interval [CI] 1.9, 3.9). Thirty-one percent were predicted to be at low risk, and their stroke rate was 1.7% per year (95% CI 0.6, 3.8). Many people with AF in this population-derived cohort had relatively low rates of stroke. Further studies to reliably stratify stroke risk in patients with AF are needed. A trial fibrillation (AF) is an independent risk factor for stroke, 1 but the absolute rate of stroke varies widely depending on coexistent vascular disease. Stroke rates range from less than 0.5% per year in patients with AF under age 60 years old without cardiopulmonary disease ("lone AF") 2,3 to 12% per year for those with prior stroke. 4,5 Risk stratification schemes for stroke in patients with AF have been derived from participants in randomized clinical trials. 3,6 However, participants with AF in these trials were, on average, younger and more often men than patients with AF in population-based cohorts. 7 The frequency and predictive value of thromboembolic risk factors in a population-derived cohort have not been examined previously.We determined the stroke rate of participants with AF in the Cardiovascular Health Study (CHS), 8,9 categorized AF participants as being at low, moderate, or high risk of stroke using two published risk stratification schemes, 10,11 and then assessed whether these schemes successfully predicted stroke during follow-up. METHODSThe CHS is a multicenter, longitudinal observational study of a population-based sample of 5,201 adults over age 65 at entry recruited from four communities. Details of study design and recruitment, which commenced in 1989, have been published. 8,9 At CHS entry, 277 participants (5.3%) were identified as having AF on the basis of entry electrocardiograms or through self-report confirmed by review of medical records. Excluding 18 people with prosthetic cardiac valves or mitral stenosis, the remaining 259 participants with nonvalvular AF are considered here. Antithrombotic therapy during follow-up was determined by their personal physicians.We assessed thromboembolic risk factors associated with stroke in two published risk stratification schemes (Table 1). 10,11 Definitions of clinical characteristics of CHS participants have been reported. 12 A history of hypertension was defined as systolic blood pressure of 160 mm Hg or higher, diastolic blood pressure of 90 mm Hg or higher, or self-reported hypertension with current use of antihypertensive medication. Prevalent myocardial infarction, angina pectoris, congestive heart failure, stroke, and transient ischemic attack (TIA) were identified by interview with subseq...

Factors Associated With Ischemic Stroke During Aspirin Therapy in Atrial Fibrillation

“…The overall rate of ischemic stroke in this cohort taking aspirin (3.3%/y) was similar to that in other recent studies of AF patients given aspirin, [17][18][19] suggesting that large fractions of younger AF patients given aspirin have low to moderate rates of stroke. On the other hand, AF patients in general medical practice are, on average, older than participants in this cohort, and consequently the fraction at high risk may be larger.…”

“…8 More research about the application of risk stratification schemes in AF to clinical practice is needed. 19 AF patients with importantly different rates of ischemic stroke can be identified. Selection of antithrombotic therapy for stroke prevention should consider the widely different stroke rates among individual patients with AF.…”

ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation

“…Among 210 patients in the population-based Cardiovascular Health Study (mean age 74 y) followed without anticoagulation, the stroke rate was 2.6% per year. 462 When stratified according to the CHADS 2 stroke risk scheme, 426 patients in the ATRIA cohort with a single stroke risk factor (32% of the cohort) who were not anticoagulated had a rate of stroke and systemic embolism of 1.5% per year (95% CI 1.2% to 1.9%). 458 Of 670 patients treated with aspirin in 6 clinical trials, the stroke rate was 2.2% per year for those with a CHADS 2 score of 1 (95% CI 1.6% to 3.1% per year).…”

2011 ACCF/AHA/HRS Focused Updates Incorporated Into the ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation

“…Among 210 patients in the population-based Cardiovascular Health Study (mean age 74 y) followed without anticoagulation, the stroke rate was 2.6% per year. 462 When stratified according to the CHADS 2 stroke risk scheme, 426 patients in the ATRIA cohort with a single stroke risk factor (32% of the cohort) who were not anticoagulated had a rate of stroke and systemic embolism of 1.5% per year (95% CI 1.2% to 1.9%). 458 Of 670 patients treated with aspirin in 6 clinical trials, the stroke rate was 2.2% per year for those with a CHADS 2 score of 1 (95% CI 1.6% to 3.1% per year).…”