Outpatient Management of Oral A n ti co ag u l at io n in A tr ial Fibrillation Julia A. Manning,

MSN, RN, CCRN, ACNP-BC

KEYWORDS  Atrial fibrillation  Oral anticoagulant  Stroke risk  Treatment  Outpatients KEY POINTS  There are currently no head-to-head trials comparing dabigatran, rivaroxaban, and apixaban, and learning to integrate them into clinical practice safely will require time and experience.  Early follow-up with regular, routine monitoring of compliance, side effects, and renal indices are prudent and are in patients’ best interest.  The results of clinical trials with newer agents have been promising.  The convenience of newer agents is truly appealing, but their full impact on the reduction of stroke risk and systemic embolism in the setting of atrial fibrillation has yet to be fully realized.

Atrial fibrillation is a commonly encountered problem in the outpatient setting, and brings with it numerous challenges including restoration of a sinus mechanism and the prevention of thromboembolism and stroke.1 Until recently, the best option for stroke prevention was the initiation of warfarin, a vitamin K antagonist. This approach presented challenges to patients and caregivers alike in the form of numerous food and drug interactions and the need for regular therapeutic monitoring with frequent dose adjustment.1 Recently, the emergence of target-specific anticoagulants that inhibit either factor Xa or thrombin has given providers safe and effective alternatives to warfarin in the management of patients with new-onset or recurring atrial fibrillation.2 Providers in the setting of primary care, internal medicine, and cardiology should be well versed in the indications, pharmacokinetics, and side effects of these newer agents, as they can provide patients with better safety, efficacy, and convenience over traditional therapy with warfarin.3 Formulating the best plan of care for patients with this very common arrhythmia should take into consideration the advantages and disadvantages of each drug, with the ultimate goal being prevention of atrial fibrillation–related stroke.

Woodlands North Houston Heart Center, 411 Lantern Bend Drive, Suite 100, Houston, TX 77090, USA E-mail address: [email protected] Crit Care Nurs Clin N Am 25 (2013) 481–487 http://dx.doi.org/10.1016/j.ccell.2013.09.002 ccnursing.theclinics.com 0899-5885/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.

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DECIDING TO ANTICOAGULATE

Atrial fibrillation is predicted to affect more than 12 million Americans by the year 2050.4 The primary concern in these patients is the occurrence of ischemic stroke, which occurs in 15% of patients with atrial fibrillation.4 There is a 5-fold increased risk of stroke in patients who have had atrial fibrillation. If a patient has had a previous stroke or transient ischemic attack (TIA), their risk of a thromboembolic event is even higher.4 To help determine stroke-risk stratification many clinicians use the CHADS2 score, a prediction tool that has been previously validated in many clinical trials (Table 1).5 The following risk factors are used: congestive heart failure, hypertension, age 75 years or older, diabetes mellitus, and stroke or TIA. Each of the risk factors counts as 1 point except stroke and TIA, each of which counts as 2 points. A score of 4 or greater is considered high risk, 2 to 3 is considered moderate risk, and less than 2 is considered low risk. In general, anticoagulation with an agent other than aspirin is recommended for patients with a score of 2 or greater.5 Patients who are at low risk may simply be treated with 81 to 325 mg of aspirin daily.5 Previously, warfarin was the mainstay of stroke-prevention therapy in the management of atrial fibrillation. The pharmacokinetics of warfarin is influenced by several factors such as diet, medications, herbal remedies, and genetics.6 The need for frequent monitoring, coupled with a very narrow therapeutic range and risk of bleeding, makes warfarin a less than desirable choice when deciding on a treatment plan for patients with atrial fibrillation.5 A therapeutic International Normalized Ratio (INR) cannot be achieved by as many as half of patients taking warfarin despite frequent monitoring.7 Clinical trial settings have shown patients to be overtreated or undertreated in approximately 4 of 12 months.8 For elderly patients, frequent monitoring of the INR alone can be a significant deterrent to compliance with prescribed therapy, given the mobility and transportation issues that many face. Home INR monitoring is an option for many patients but requires strict compliance with testing and reporting of results, and can also be cost prohibitive, eliminating many patients as candidates. The emergence of several target-specific oral anticoagulants (TSOAs) is revolutionizing the way atrial fibrillation is treated in the outpatient setting. TSOAs have given providers and patients better options for stroke prevention, in some cases resulting in an improvement patients’ quality of life. In patients with atrial fibrillation, dabigatran, rivaroxaban, and apixaban specifically have been shown to be more efficacious than warfarin in the prevention of stroke and systemic embolism.9 Monitoring of these agents is not necessary except in patients with renal or hepatic impairment, patients older than 75 years, the very obese, or those with very low body weight.8 In addition,

Table 1 Calculation of the CHADS2 score5 Condition

Points

Congestive heart failure

1

Hypertension (treated with at least 1 medication or blood pressure consistently >140/90 mm Hg)

1

Age >75 y

1

Diabetes mellitus

1

Prior Stroke or transient ischemic attack

2

Score: 4 5 high risk; 2–3 5 moderate risk; 2 or less 5 low risk.

Outpatient Management of Oral Anticoagulation

TSOAs appear to have a very favorable safety profile and require little or no ongoing monitoring, which makes them an attractive alternative to warfarin.9 DABIGATRAN

Dabigatran is an oral, direct thrombin inhibitor, which prevents the conversion of fibrinogen to fibrin and thrombin-inducing platelet aggregation.3 It is indicated for the treatment of nonvalvular atrial fibrillation. In the noninferiority study Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY), dabigatran was compared at 2 fixed doses with dose-adjusted warfarin (INR range 2–3). The study was a randomized, multicenter, open-label trial. Patients with atrial fibrillation and an increased risk of stroke were assigned to one of the treatment groups. Exclusion criteria included patients with a stroke in the last 14 days, a severe stroke in the previous 6 months, major heart-valve disease, any risk factor for hemorrhage, pregnancy, active hepatic disorder, and creatinine clearance (CrCl) of 30 mL/min.4 Approximately one-third of the patients enrolled had a CHADS2 score of 3 or more. Patients in the warfarin arm were able to achieve therapeutic INR only 64% of the time. In patients randomized to dabigatran 110 mg, the incidence of stroke or systemic embolism was 1.5% per year. For patients randomized to dabigatran 150 mg, the incidence was 1.1% per year compared with 1.7% per year for those in the warfarin group. Occurrence of hemorrhagic stroke was lower with dabigatran (0.12%/y with 110 mg and 0.10%/y with 150 mg vs 0.38%/y with warfarin; P

Outpatient management of oral anticoagulation in atrial fibrillation.

Atrial fibrillation is a commonly encountered problem in the outpatient setting. This article presents an overview of the outpatient management of ora...
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