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INTRODUCTION

Atrial fibrillation (AF) is a supraventricular arrhythmia caused by abnormal impulse formation and propagation within the atrial tissue.¹ AF is the most commonly encountered cardiac arrhythmia, affecting more than 30 million individuals around the world.² According to the Centers for Disease Control and Prevention, 2.7 to 6.1 million Americans have AF. The prevalence of AF is significantly higher in elderly patients: it occurs in roughly 2% of people younger than 65 years of age and 9% of people 65 years and older.³ The increasing prevalence of predisposing conditions such as obesity, coronary artery disease, hypertension, heart failure, diabetes mellitus, and chronic kidney disease (CKD), as well as an aging population, will contribute to greater rates of AF in the future.

AF is associated with significant morbidity and mortality. In patients with AF, the risk of all-cause mortality is 1.5- to 2-fold higher than in patients without AF. One of the most devastating complications of AF is stroke, and AF accounts for 20% to 30% of all strokes. Patients with AF are 4 to 5 times more likely to experience stroke than the general population.⁴ The risks of in-hospital mortality, 30-day mortality, and increased length of hospital stay are significantly greater in those with AF than in those without.⁵ 

In addition to AF alone, several additional risk factors for ischemic stroke in this population have been identified. Independent risk factors for stroke include a history of prior stroke or transient ischemic attack (TIA), structural heart disease, hypertension, age, diabetes, female sex, vascular disease, and heart failure. The cornerstone of ischemic stroke prevention in AF is anticoagulation (AC) therapy. For patients at significant risk of stroke, providers must navigate the realm of oral AC, which currently includes warfarin, dabigatran, rivaroxaban, apixaban, and edoxaban.

GUIDELINE RECOMMENDATIONS FOR AC IN AF

In the United States (U.S.), several organizations, including the American College of Chest Physicians (CHEST), the American Heart Association (AHA), and the American College of Cardiology (ACC), have published guidelines on the management of AC in patients with AF. The CHEST guidelines recommend utilizing the CHA₂DS₂-VASc score to determine the risk of stroke in patients with AF. For male patients with a CHA₂DS₂-VASc score of 1 and female patients with a score of 2, the guidelines recommend initiation of AC. For eligible patients, CHEST recommends a direct oral anticoagulant (DOAC) over warfarin. Additionally, for patients with labile international normalized ratios (INRs) while taking warfarin, the guidelines recommend considering changing to DOAC therapy. Lastly, for patients experiencing an episode of bleeding on warfarin who have a history of unprovoked bleeding or are at high risk of bleeding (e.g., elderly, abnormal liver function, alcohol use), providers should consider the use of apixaban or edoxaban.⁴

While many of the recommendations in the joint AHA/ACC guidelines mirror the CHEST guidelines, there are differences worth noting. The AHA/ACC guidelines offer a strong recommendation for AC in men with a CHA₂DS₂-VASc score of 2 or higher and in women with a score of 3 or higher. In alignment with the CHEST guidelines, the AHA and ACC recommend the use of a DOAC over warfarin for non-valvular AF (NVAF) and suggest these agents may also be beneficial in patients with poorly controlled warfarin therapy. NVAF excludes patients with moderate to severe mitral valve stenosis, as well as mechanical heart valves. These guidelines go further than the CHEST guidelines, recommending the use of warfarin or apixaban in patients with end-stage CKD, patients who are on dialysis, and patients who have an estimated creatinine clearance (CrCl) of less than 15 mL/min.⁶