Atrial Fibrillation and Thromboembolism: A Decade of Progress in Stroke Prevention

Abstract

Atrial fibrillation is associated with a sixfold increased risk for stroke. More than a dozen published randomized trials of anticoagulants or antiplatelet agents for stroke prevention provide solid evidence on which to base antithrombotic prophylaxis. Adjusted-dose warfarin reduces risk for stroke by about 60% compared with placebo, aspirin reduces this risk (primarily for nondisabling stroke) by about 20% compared with placebo, and warfarin reduces it by about 40% compared with aspirin. Warfarin provides maximal protection against stroke at international normalized ratios of 2.0 to 3.0. Risk stratification of patients with atrial fibrillation identifies those who potentially benefit most or least from anticoagulation; this is important because a substantial percentage of patients with atrial fibrillation have relatively low rates of stroke if they are given aspirin. Many elderly patients with recurrent intermittent atrial fibrillation experience high rates of stroke and benefit from anticoagulation. The value of precordial or transesophageal echocardiography in addition to clinical risk stratifiers for stratifying stroke risk is controversial. Altered hemostasis favoring thrombosis may contribute to formation of atrial appendage thrombus, but these conditions remain ill defined. The past decade has brought unprecedented progress toward understanding thromboembolism in patients with atrial fibrillation and has changed the clinical perspective of a prevalent cardiac arrhythmia into an important opportunity for stroke prevention. Making the most of this promise calls for appreciation of the epidemiology of atrial fibrillation and the concept of risk specificity in the face of diverse therapeutic options.

Selecting Patients With Atrial Fibrillation for Anticoagulation

“…The ability to characterize low-risk AF patients with confidence allows clinicians to identify patients who can safely be treated with aspirin, sparing them the risk of bleeding, cost, and inconvenience from anticoagulant therapy. 39,40 Although the Framingham scheme identified the largest fraction of low-risk patients (almost half of the primary prevention cohort had a Framingham score of 7 or less), the additional low-risk patients identified had Ϸ2 strokes per 100 patient-years, a rate substantially greater than other low-risk cohorts.…”

Fibrilación auricular: enfoque para el médico no cardiólogo

“…Pinto y cols., reportaron recientemente que solo el 5% de los pacientes con FA que consultaban a urgencias tenían INR en rango terapéutico (15), lo cual está en consonancia con la baja tasa de tiempo en rango terapéutico que se ha demostrado en pacientes participantes de estudios clínicos controlados (66% del tiempo en rango terapéutico) (21,22,28,30,(33)(34)(35)37) y en registros de la comunidad (44%) (11, 19, 23-26, 29, 36, 38, 43, 44). Está claramente demostrado que un tiempo en rango terapéutico menor del 60% para warfarina se asocia a pérdida del beneficio de anticoagulación (1,5,11,12,16,17,20,29), observándose en este grupo de pacientes un aumento tanto del riesgo de eventos tromboembólicos como de sangrado, cuando se compara con pacientes con tiempo en rango terapéutico del 70% o más (1,5,11,12,16,17,20,29). La implementación de clínicas de anticoagulación ha mejorado las tasas de tiempo en rango terapéutico logradas por los pacientes usuarios de warfarina y otros cumarínicos (1,5,6,8,9,10,11,17,18,26,29).…”

Capsule Commentary on Andrade et al., Clinical Benefit of American College of Chest Physicians versus European Society of Cardiology Guidelines for Stroke Prophylaxis in Atrial Fibrillation

“…About 15-20 % of patients suffering from AF develop strokes. 2 In view of an aging population, the higher physiological propensity for bleeding in the elderly and the overwhelming issues of polypharmacy, the decision for the use of anticoagulation is critical.…”