Treatment Pathways for Patients With Atrial Fibrillation

J. A. Hodgkinson; C. J. Taylor; F. D. R. Hobbs

Disclosures

Int J Clin Pract. 2012;66(1):44-52. 

In This Article

Background

Atrial fibrillation (AF) is a common rhythm disorder and the most common chronic arrhythmia. AF is associated with increased morbidity and mortality,[1] and, in particular, is a major independent risk factor for stroke,[2] particularly in older patients. The prevalence of AF in the UK is more than 12/1000, but this increases to at least 10% in people aged 85 years and over[3] or to 16% according to recent data.[4]

Atrial fibrillation represents a challenging arrhythmia. A rational approach to management of the individual case depends on careful assessment of the temporal pattern of the arrhythmia, any associated cardiovascular disease and any particular features suggesting the advisability or risks of specific treatment regimens. The nature of an arrhythmia and of individual patient factors changes over time, requiring a flexible approach to long-term treatment that may be defined only after months or years.[5] In particular, key considerations are the use of anticoagulants and/or antiplatelets as antithrombotic therapy, and the pursuance of a rate- or rhythm-control approach.

Anticoagulants and the Underuse of Warfarin

There is a strong evidence base for use of anticoagulation, but it is associated with monitoring costs, and has previously been linked to a higher risk of haemorrhage compared with antiplatelet agents such as aspirin.[6–8] However, the BAFTA Trial showed no difference in haemorrhage risk, but a 52% reduction in stroke risk comparing use of warfarin with aspirin in over 75s with AF.[9]

The NICE atrial fibrillation guidelines[10] recommend that the decision to prescribe anticoagulants should be made on the basis of stroke risk, and that on the basis of this assessment, people are divided into three categories (Figure 1).

Figure 1.

Categories of stroke risk and appropriate treatment according to NICE AF guidelines

This closely mirrors CHADS2 (Figure 2), a scoring system used for patients with AF to determine their risk of stroke, and therefore decide who should receive anticoagulation and who should not[11] and that has been validated amongst an independent population.[12]

Figure 2.

CHADS2 score for AF stroke risk

Warfarin is underused for stroke prevention in AF.[13–15] NICE estimated that an additional 165,946 patients should be on warfarin – almost 50% of those estimated as requiring warfarin.[16]

This pattern of underuse of warfarin recurs internationally. An analysis of trends in the medical therapy of AF in the United States from 1991 through 2000 found that only 46.5% of patients at high risk for stroke were taking anticoagulants in 1999–2000.[17] Even US research as recent as 2005–2008 found that warfarin use varied inversely with CHADS2.[18]

A cross-sectional study of 1178 patients with AF attending 12 emergency departments (EDs) in Spain found that 89% of the patients not taking anticoagulants had indications for anticoagulation, with 63% of these patients having two or more risk factors.[19] The pattern of underuse of warfarin recurs in Switzerland,[20] Japan[21] and Greece.[22]

In this article, we consider the relationship between stroke risk scores (using CHADS2) and use of anticoagulant therapy, in particular whether there is a relationship in the probability of transition to or away from particular treatment regimen by risk strata, and if there is any evidence of a change in this relationship in more recent times. Our hypothesis is that, comparative to patients in lower stroke risk categories (as measured by CHADS2 score), patients with higher CHADS2 scores are less likely to discontinue anticoagulant therapy or, if not started on anticoagulant treatment, more likely to be transferred to anticoagulant therapy, in keeping with guideline recommendations.

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