Stroke and thromboembolic event rates in atrial fibrillation according to different guideline treatment thresholds: A nationwide cohort study.

Peter Brønnum Nielsen,Torben Bjerregaard Larsen,Flemming Skjøth,Thure Filskov Overvad,Gregory Y H Lip

doi:10.1038/srep27410

Abstract

Contemporary guidelines suggest anticoagulant treatment decisions in atrial fibrillation (AF) patients to be based on risk stratification for stroke. However, guidelines do not agree on the threshold for treatment initiation. We explored the variation in thromboembolic event rates in a non-anticoagulated AF population, according to different guideline threshold and methodological approaches. AF patients between 1998 and 2014 free from anticoagulant treatment were identified. Event rates for ischemic stroke and ischemic stroke/systemic embolism were explored. The overall ischemic stroke rate was 3.20 per 100 person-years (‘formal rate assessment’). For patients with a CHA2DS2-VASc score of 1 the ischemic stroke rate was 0.97 when using a ‘formal rate assessment’, 0.62 when using a ‘conditioning on the future’ approach, and 0.93 when using a ‘censoring approach’. Rates for thromboembolism for the ‘European treatment threshold’ (CHA2DS2-VASc score of 1, males only) ranged 1.17 to 1.53. Rates for the ‘U.S. treatment threshold’ (CHA2DS2-VASc of 2) ranged from 1.95 to 2.33. Thromboembolic event rates differed markedly in non-anticoagulated AF patients according to the conflicting European and U.S. guideline treatment thresholds. Second, the choice of methodological approach has implications, thus we recommend using the censoring approach for event rate estimation among AF patients not on treatment.

Highlights

Class IIb recommendation on either no treatment, aspirin therapy, or oral anticoagulant treatment in Atrial fibrillation (AF) patients with a CHA2DS2-VASc score of 111
Study data was obtained by cross-linkage of three nationwide databases: (I) the Danish National Prescription Registry, which records purchase date, Anatomical Therapeutic Chemical [ATC] classification code, and package size for every prescription purchase in Denmark since[18]; (II) the Danish National Patient Register which contains discharge diagnoses for all hospital admissions in Denmark defined in terms of International Classification of Diseases revision 10 (ICD-10) since 199419; and (III) the Danish Civil Registration System which holds information on sex, date of birth, vital and emigration status[20]
We restricted the cohort by excluding those with expected valvular AF; patients who immigrated within two years prior to their AF diagnosis were excluded

Summary

Introduction

Class IIb recommendation on either no treatment, aspirin therapy, or oral anticoagulant treatment in AF patients with a CHA2DS2-VASc score of 111. Guideline writing committees have based their recommendations on data from the Danish nationwide registries[13,14]. Friberg et al suggested that oral anticoagulant treatment was unlikely to benefit AF patients with a CHA2DS2-VASc score of 1 based on data from the nationwide Swedish cohort[16]. We aimed to investigate the thromboembolic event rates in a non-anticoagulated atrial fibrillation population, in relation to different guideline cut-off values. We studied the impact of different methodological approaches when investigating event rates in an untreated population

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Conclusion