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Risk of stroke and transient ischaemic attack in patients with a diagnosis of resolved atrial fibrillation: retrospective cohort studies

BMJ 2018; 361 doi: https://doi.org/10.1136/bmj.k1717 (Published 09 May 2018) Cite this as: BMJ 2018;361:k1717

Opinion: The importance of asking the right research question

Authors' response

We agree with Dr Wicke that the use of an AF resolved code means patients may be misclassified as having resolved AF. We believe it is unlikely that general practitioners will undertake seven day or 28 day monitoring to confirm the absence of AF before using this code, therefore it is difficult to envisage a practical alternative to a definition of AF resolved based on clinical judgement. We also are aware that AF may recur silently: even after catheter ablation recurrence occurs in 25% within 1 year and then a further 5% annually (1,2).

Dr Abbott suggests that the incidence of stroke in AF patients in our cohort is lower than in the original clinical trials and lower still in those with AF resolved. Dr Abbott argues they therefore may not benefit sufficiently to justify anticoagulants. However, incidence of stroke has declined markedly in the 30 years since the original clinical trials of warfarin in AF and it could equally be argued that no AF patients benefit sufficiently to justify treatment.

In fact we observed the incidence of stroke or TIA in patients with AF to be 17 per 1000 person years, consistent with the incidence of stroke reported for the warfarin group in a more recent trial comparing apixaban to warfarin (15 per 1000 person years). (3) We also found that from 2013 onwards the incidence of stroke or TIA with resolved AF and ongoing AF were similar: adjusted incidence rate ratio 0.96 (95% CI: 0.67 to 1.39). We agree with Dr Abbott that AF is a spectrum and as detection technologies improve the stroke risk associated with more intermittent AF is as yet unquantified but is likely to be lower than with permanent AF. (4)

Given the high probability of misclassification and of AF recurrence, we do not share Dr Parmar’s confidence that strokes after resolved AF have a different pathophysiology to those with ongoing AF. Dr Parmar suggests antiplatelet treatment as an alternative. But it is unclear that antiplatelet treatment offers advantages over anticoagulants as evidence does not support the view that it is safer: relative risk of major bleeding is 1.01 (95% CI, 0.69-1.48). (5)

Yours sincerely,

Tom Marshall, Professor of Public Health & Primary Care
Krishnarajah Nirantharakumar, Senior Lecturer in Public Health
Nicola Adderley, Lecturer in Public Health

1. Arya A et al Long-term results and the predictors of outcome of catheter ablation of atrial fibrillation using steerable sheath catheter navigation after single procedure in 674 patients. Europace. 2010 Feb;12(2):173-80. doi: 10.1093/europace/eup331. Epub 2009 Nov 3.
2. Tao H et al Predictors of very late recurrence of atrial fibrillation after circumferential pulmonary vein ablation. Clin Cardiol. 2008 Oct;31(10):463-8. doi: 10.1002/clc.20340.
3. Granger CB, Alexander JH, McMurray JJ, et al. Apixaban versus warfarin in patients with atrial fibrillation. New Eng J Med 2011;365:981-92.
4. Takabayashi K, Hamatani Y, Yamashita Y, Takagi D, Unoki T, Ishii M, Iguchi M, Masunaga N, Ogawa H, Esato M, Chun YH, Tsuji H, Wada H, Hasegawa K, Abe M, Lip GY, Akao M. Incidence of Stroke or Systemic Embolism in Paroxysmal Versus Sustained Atrial Fibrillation: The Fushimi Atrial Fibrillation Registry. Stroke. 2015 Dec;46(12):3354-61. doi: 10.1161/STROKEAHA.115.010947. Epub 2015 Oct 29.
5. Melkonian M, Jarzebowski W, Pautas E, Siguret V, Belmin J, Lafuente-Lafuente C. Bleeding risk of antiplatelet drugs compared with oral anticoagulants in older patients with atrial fibrillation: a systematic review and meta-analysis. J Thromb Haemost. 2017 Jul;15(7):1500-1510. doi: 10.1111/jth.13697. Epub 2017 May 11.

Competing interests: No competing interests

23 May 2018
Tom Marshall
Professor of Public Health & Primary Care
Krishnarajah Nirantharakumar, Senior Lecturer in Public Health; Nicola J Adderley, Lecturer in Public Health
University of Birmingham
Birmingham, UK