title: Atrial fibrillation patients categorized as "not for anticoagulation" according to the 2014 Canadian Cardiovascular Society algorithm are not "low risk".
abstract: BACKGROUND
  Oral anticoagulation (OAC) is highly effective for stroke prevention in nonvalvular atrial fibrillation. We explored rates of stroke/thromboembolism/transient ischemic attack among the "OAC not recommended" patient group defined according to the 2014 Canadian Cardiovascular Society (CCS) algorithm (based on the Congestive Heart Failure, Hypertension, Age, Diabetes, Stroke/Transient Ischemic Attack [CHADS2] score) who would have been offered OAC using the European Society of Cardiology (ESC) guidelines approach (based on the Congestive Heart Failure, Hypertension, Age [≥75 years], Diabetes, Stroke/Transient Ischemic Attack, Vascular Disease, Age [65-74 years], Sex [Female]; CHA2DS2-VASc score).
  
  
  METHODS
  We identified 22,582 nonanticoagulated patients age < 65 years with a CHADS2 score of 0 who were stratified according to the CHA2DS2-VASc score, except female sex, which would be an indication for OAC according to the ESC guidelines. Event rates for each risk strata were compared using Cox proportional hazard ratios.
  
  
  RESULTS
  The overall rate of the combined end point of ischemic stroke/systemic embolism/transient ischemic attack was 4.32 per 100 person-years (95% confidence interval [CI], 3.26-5.74) at 1 year, among the patients who would have had an indication for OAC therapy according to ESC guidelines and "OAC not recommended" according to CCS algorithm. This corresponded to an adjusted hazard ratio of 3.08 (95% CI, 2.21-4.29) relative to the subgroup with no indication for OAC according to the ESC guidelines. A subgroup of patients with previous vascular disease and CHADS2 score of 0 (ie, recommended only aspirin treatment according to the CCS algorithm) had an event rate of 4.84 (95% CI, 3.53-6.62) per 100 person-years at 1-year follow-up.
  
  
  CONCLUSIONS
  Based on the 2014 CCS algorithm, the "OAC not recommended" subgroup can have a high 1-year stroke rate overall, showing that such patients are not "low risk." Use of the ESC guideline approach (based on the CHA2DS2-VASc) offers refinement of stroke risk stratification in such patients.
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Aalborg, Denmark; University of Birmingham, Centre for Cardiovascular Sciences, City Hospital, Birmingham, United Kingdom. Electronic address: g.y.h.lip@bham.ac.uk.
authors.forename: Gregory Y H
authors.initials: GY
authors.lastname: Lip
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Aalborg, Denmark.
authors.forename: Peter Brønnum
authors.initials: PB
authors.lastname: Nielsen
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Aalborg, Denmark; Department of Cardiology, Aalborg AF Study Group, Aalborg University Hospital, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Skjøth
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Aalborg, Denmark; Department of Cardiology, Aalborg AF Study Group, Aalborg University Hospital, Denmark.
authors.forename: Lars Hvilsted
authors.initials: LH
authors.lastname: Rasmussen
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Aalborg, Denmark; Department of Cardiology, Aalborg AF Study Group, Aalborg University Hospital, Denmark.
authors.forename: Torben Bjerregaard
authors.initials: TB
authors.lastname: Larsen
mesh_terms: D000368:Aged; D000465:Algorithms; D000925:Anticoagulants / Q000494:pharmacology*; D001281:Atrial Fibrillation / Q000150:complications / Q000628:therapy*; D002545:Brain Ischemia / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D002170:Canada / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D017410:Practice Guidelines as Topic; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012955:Societies, Medical
chemical_list: D000925:Anticoagulants