Atrial fibrillation or on the sleeping enemy

Atrial fibrillation (AF) is the most common arrhythmia in the general population, affecting 4% of patients over 65 and up to 15% of those over 80. It is estimated that nationally it can affect approximately one million people, being a relevant cause of disability, worsening of quality of life in relation to the risk of cerebrovascular disease, as well as cardiac decompensation. Non-valvular AF must be distinguished from that produced by rheumatic mitral stenosis, mechanical prostheses in which the risk of embolism is much higher.

Different scales have been developed that weigh the emboligenous (CHADS2, CHA2DS2-VASc) and haemorrhagic (HAS-BLED) risks. Of the risk factors and markers described, the control of those potentially modifiable such as adequate control of blood pressure, the concomitant use of certain medications (especially antiaggregants, NSAIDs and alcohol), and especially the control of possible lability or lack of control of the INR (which demonstrates whether the patient is truly anticoagulated) is of great relevance.

The classic anticoagulants, vitamin K antagonists (AVK), have been used since the middle of the 20th century. They are medicines with a narrow therapeutic margin, which interact with other medicines and with food, and the prothrombin time must be controlled by the INR on a regular basis, which implies a dependence on health resources, but on the other hand there is a great knowledge of their management. Since 2009, new oral anticoagulants (NACO) such as dabigatran, a thrombin inhibitor, and later factor Xa inhibitors such as rivaroxaban, apixaban, have appeared, which may be effective and safe alternatives in patients with hypersensitivity to AVK, or in the case of correct control if they present emboligenous or haemorrhagic complications and especially in those patients whose INR is difficult to control adequately. As shown in the table, the most effective is dabigatran at a dose of 150 mg every 12 hours, taking into account losses and the design of the RE-LY study, and the safest would be apixaban at a dose of 5 mg/12 hours (oedoxaban 30 mg per day, the risk of bleeding is lower, as it is not commercially available).  It is significant that in clinical trials conducted with an adequate sample size the control group with AVK achieves at best a therapeutic range time (TRT) of 65%, thus demonstrating the importance of periodic follow-up and monitoring of the INR. Likewise, those patients with frequent decompensation, mainly cardiorespiratory, polymedicated with high risk of interactions or those with renal insufficiency should be monitored more closely. In any case, a certain degree of prudence must be maintained in the interventions, adapting the treatments to the patient's care objectives, considering the pharmacovigilance results, since the average duration of the medicines in clinical trials has been about 2 years, without the availability of an antidote in the event of haemorrhage.

In March 2014 the American Heart Association* and in May the neurology association** published respectively the update of the clinical practice guide on the management of VASF, determining that in patients with CHA2DS2-VASc ≥ 2 should be anticoagulated initially with acenocoumarol and taking into account the rotation to NACS in case of inadequate control or complications. Anti-aggregation treatment is much less effective and yet the risk of bleeding is similar, also taking into account that as a secondary prevention of stroke in women it decreases its effect from the age of 77. With the ageing population, the adequate management of cardio-embolic control and of the bleeding risk is fundamental as measures to prevent disability, also taking into account the preferences, costs and interactions to adapt the therapies.

"Intelligence consists not only of knowledge, but also of the ability to apply knowledge in practice".
Aristotle

*2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation

**2014 Guidelines for the Prevention of Stroke in Women. A Statement for Healthcare Professionals From the American Heart Association/American Stroke Association