**1. Introduction**

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice with a strong impact on public health*.* The prevalence in the general population is 0.4% and their incidence increases markedly with age to reach 4-5% in patients over 65 years and 9% in patients older than 80 years [1]. The main complication associated with this disease is the development of an embolic event, peripheral or cerebral, strokes being caused by the AF the most serious and worse prognosis. The risk that a patient suffers a stroke with AF is related to the presence of other cardioembolic risk factors: hypertension, diabetes mellitus, heart failure or left ventricular systolic dysfunction, moderately severe, age over 75 years, female, vascular disease or stroke have shown a previous cerebral (transient or establish‐ ed). These risk factors are reflected in the scales CHADS2 or CHA2DS2-VASC used today to evaluate this type of patient.

In the management of patients with AF, the most important to improve prognosis is correct indication of anticoagulant therapy. For over 60 years using vitamin K antagonists (VKAs), especially warfarin and acenocoumarol, have been shown in several studies a reduction of 70% risk of stroke in AF patients correctly anticoagulated compared with only 22% reduc‐ tion of antiplatelet drugs, or a nonsignificant 19% reduction with acetylsalicylic acid. Thus, oral anticoagulants (OACs) are recommended in AF patients at moderate-high risk for sroke and tromboembolism [2]. The VKAs are drugs with proven efficacy, specific antidote in case of bleeding, possibility of discontinuing medication urgently and low cost. However, VKAs have limitations that affect the quality of life of patients and increase morbidity: narrow therapeutic window (International normalized ratio, INR 2.0-3.0) [3], unpredictable re‐ sponse, systematic control of bleeding, frequent dose adjustments and numerous food and drug interactions. Also, scenarios such as intercurrent infections and other medical condi‐ tions can also modify the values of the INR [4]. These results indicate that it is important to

properly cited.

© 2013 Cid-Conde and López-Castro; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

stratify each patient, both the risk of stroke such as bleeding, to individually assess what the best therapeutic approach in each case.

Given the limitations of CHADS2 scale, a large proportion of patients are classified as inter‐ mediate risk and to the omission of potential risk factors for thromboembolism, there is the scale CHA2DS2-VASc [9,10]. This new scale is more comprehensive as additional risk factors: the presence of vascular disease, a younger age range than the CHADS2 and female category (Table 3). The patients with a grade of 0 are at low risk and should not be treated. The rest should be considered for oral anticoagulation, establishing the risk of bleeding by HAS-BLED scale (Table 4) [11]. In patients with a HAS-BLED score ≥3, caution and regular review are recomended and to correct the potentially reversible risk factors for bleeding. A high

New Oral Anticoagulants in Atrial Fibrillation

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HAS-BLED score per se should not be used to exclude patients from OAC therapy.

**Table 3.** Stroke risk stratification with the CHA2DS2-VASc score

each)

**Table 4.** HAS-BLED risk criteria

**CHA2DS2-VASc acronym Score** CHF or LVEF ≤ 40% 1 Hypertension 1 Aged ≥ 75 years 2 Diabetes mellitus 1 Stroke / TIA / Thromboembolism 2 Vacular disease 1 Aged 65-74 years 1 Sex category (Female) 1 **Maximum score 9**

**HAS-BLED risk criteria Score** Hypertension 1

Stroke 1 Bleeding 1 Labile INRs 1 Elderly (age > 65) 1 Drugs or alcohol (1 point each) 1 or 2

If a patient has a rating of less than 2 on the CHADS2 scale, it also assesses the amendment CHA2DS2-VASc, although this could be applied directly: if the score is zero, who are at low risk, with none of the risk factors, no antithrombotic treatment is indicated and if the score is

1 or 2

Abnormal renal or liver function (1 point

Due to the complexity of the use of VKAs in routine clinical practice in the last decade has developed an extensive research activity and has seen the introduction of new oral anticoa‐ gulants (NOACs): The direct thrombin inhibitors (dabigatran) and factor Xa (rivaroxaban and apixaban) that do not possess the disadvantages of the VKAs. These drugs are charac‐ terized by rapid onset of action, low potential for drug and food interactions and a predicta‐ ble anticoagulant effect that avoids the need to monitor coagulation (Table 1) [5-7].


**Table 1.** Comparative features of VKAs and NOACs
