TRIP Answers

26 June 2008 note: This question is over 2 years old and may differ to any new research.

In answering this question, we do not know whether this is lone atrial fibrillation (AF), valvular or non-valvular AF.

The guidelines on atrial fibrillation we consulted all suggest patients under 65 years old with no high to moderate risk factors for stroke should be offered aspirin for thromboprophylaxis. For example, please refer to the clinical scenario on antithrombotic therapy in CKS guideline on atrial fibrillation. [1]. However, they do not explicitly state how long patients should remain on thromboprophylaxis.

However, The Royal College of Physicians guideline on atrial fibrillation notes in its section for antithrombotic therapy for persistent AF (section 6.3):

“Patients with persistent AF may be treated with either a rate-control or rhythm-control treatment strategy. Where a rhythm-control treatment strategy is chosen, there is the need for appropriate use of antithrombotic therapy to prevent acute stroke or other thromboembolic events occurring during or shortly after cardioversion. Where a rate-control strategy is chosen, patients should be treated as outlined for permanent AF (see Chapter 7).

It is known that the presence of AF increases the risk of thromboembolic stroke, but it is less clear whether this risk can be reduced by cardioversion (ECV or PCV) to normal sinus rhythm, assuming sinus rhythm is maintained and antithrombotic therapy is continued. The rate versus rhythm-control trials have not resolved this issue as many of the patients relapsed into
AF and had been administered inadequate thromboprophylaxis (see section 6.1). Appropriate thromboprophylactic measures are essential in patients considered for cardioversion since it has been shown that cardioversion of AF of more than 48 hours duration increases the short-term (peri-cardioversion) risk of stroke and thromboembolism.

Data from the rate-control versus rhythm-control trials suggest that consideration should be given to long-term anticoagulation in patients at high risk of stroke and/or AF recurrence in view of the frequent asymptomatic recurrences of the arrhythmia leading to thromboembolism in the presence of risk factors.” [2]

A final search of the guideline literature found the Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy guideline and this recommends:

Long-term Antithrombotic Therapy for Chronic Atrial Fibrillation (AF) or Atrial Flutter, Anticoagulants and Antiplatelet Agents
Atrial Fibrillation

1. In patients with persistent (also known as "sustained," and including patients categorized as "permanent" in certain classification schemes) or paroxysmal (intermittent) AF (PAF) at high risk of stroke (i.e., having any of the following features: prior ischemic stroke, transient ischemic attack (TIA), or systemic embolism, age >75 years, moderately or severely impaired left ventricular systolic function and/or congestive heart failure, history of hypertension, or diabetes mellitus), the guideline developers recommend anticoagulation with an oral vitamin K antagonist (VKA), such as warfarin (target international normalized ratio [INR], 2.5; range 2.0 to 3.0) (Grade 1A).

2. In patients with persistent AF or PAF, age 65 to 75 years, in the absence of other risk factors, the guideline developers recommend antithrombotic therapy (Grade 1A). Either an oral VKA, such as warfarin (target INR, 2.5; range 2.0 to 3.0), or aspirin, 325 mg/d, are acceptable alternatives in this group of patients who are at intermediate risk of stroke.

3. In patients with persistent AF or PAF <65 years old and with no other risk factors, the guideline developers recommend aspirin, 325 mg/d (Grade 1B).
Underlying values and preferences: Anticoagulation with an oral VKA, such as warfarin, has far greater efficacy than aspirin in preventing stroke, and particularly in preventing severe ischemic stroke, in AF. The guideline developers recommend the option of aspirin therapy for lower-risk groups (see above); estimating the absolute expected benefit of anticoagulant therapy may not be worth the increased hemorrhagic risk and burden of anticoagulation. Individual lower-risk patients may rationally choose anticoagulation over aspirin therapy to gain greater protection against ischemic stroke if they value protection against stroke much more highly than reducing risk of hemorrhage and burden of managing anticoagulation.” [3]

References
1. CKS. Atrial fibrillation. January 2007. (http://www.cks.library.nhs.uk/atrial_fibrillation/management/quick_answers/scenario_antithrombotic_treatment)
2. Royal College of Physicians. Atrial fibrillation. 2006. (http://www.rcplondon.ac.uk/pubs/contents/d74e2562-519e-46b4-b952-48433c6076b7.pdf)
3. Singer DE, Albers GW, Dalen JE, Go AS, Halperin JL, Manning WJ. Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004 Sep;126(3 Suppl):429S-56S. (http://www.guideline.gov/summary/summary.aspx?doc_id=5894&nbr=3880&ss=6&xl=999)