Thromb Haemost
DOI: 10.1055/a-1541-3885
Stroke, Systemic or Venous Thromboembolism

Risk of Ischemic Stroke in Asymptomatic Atrial Fibrillation Incidentally Detected in Primary Care Compared with Other Clinical Presentations

1  Institute for Epidemiology, Statistics and Informatics GmbH, Frankfurt, Germany
1  Institute for Epidemiology, Statistics and Informatics GmbH, Frankfurt, Germany
Ben Freedman
2  Heart Research Institute, Charles Perkins Centre, University of Sydney, Sydney, Australia
3  Department of Cardiology, Concord Hospital, Sydney, Australia
4  ANZAC Research Institute, Concord Hospital, Sydney, Australia
› Author Affiliations
Funding None.


Background It is uncertain whether stroke risk of asymptomatic ambulatory atrial fibrillation (AA-AF) incidentally detected in primary care is comparable with other clinical AF presentations in primary care or hospital.

Methods The stoke risk of 22,035 patients with incident nonvalvular AF from the United Kingdom primary care Clinical Practice Research Datalink with linkage to hospitalization and mortality data was compared with 23,605 controls without AF (age- and sex-matched 5:1 to 5,409 AA-AF patients). Incident AF included 5,913 with symptomatic ambulatory AF (SA-AF); 4,989 with primary and 5,724 with nonprimary hospital AF discharge diagnosis (PH-AF and non-PH-AF); and 5,409 with AA-AF. Ischemic stroke adjusted subhazard ratios (aSHRs) within 3 years of AA-AF were compared with SA-AF, PH-AF, non-PH-AF, and no AF, accounting for mortality as competing risk and adjusted for ischemic stroke risk factors.

Results There were 1,026 ischemic strokes in 49,544 person-years in patients with incident AF (crude incidence rate: 2.1 ischemic strokes/100 person-years). Ischemic stroke aSHR over 3 years showed no differences between AA-AF and SA-AF, PH-AF, and non-PH-AF groups (aSHR: 0.87–1.01 vs. AA-AF). All AF groups showed a significantly higher aSHR compared with no AF.

Conclusion Ischemic stroke risk in patients with AA-AF incidentally detected in primary care is far from benign, and not less than incident AF presenting clinically in general practice or hospital. This provides justification for identification of previously undetected AF, e.g., by opportunistic screening, and subsequent stroke prevention with thromboprophylaxis, to reduce the approximately 10% of ischemic strokes related to unrecognized AF.

Author Contributions

All authors had full access to all the data in the study and C.M. takes responsibility for the integrity of the data and accuracy of the data analysis. Conception or design: all authors. Data acquisition and analysis: C.M., C.W. Data interpretation: all authors. Drafting of the manuscript: all authors. Critical revision for important intellectual content: all authors. Final approval of the version to be submitted: all authors.

Data Availability

Clinical Practice Research Datalink data cannot be shared because of licensing restrictions.


The views expressed are those of the authors and not official positions of the institutions. Part of the information reported in this manuscript was presented at the European Society of Cardiology Congress, August 26–30, 2017, Barcelona, Spain.

Ethical Approval

The study protocol was approved by the Independent Scientific Advisory Committee for CPRD research (Protocol 11_024RAMn). No further ethics approval was required for the analysis of the data as the CPRD Group had obtained ethical approval from a multicenter research ethics committee for all purely observational research using CPRD data, namely, studies that do not include patient involvement. Data that could directly identify patients were not collected in this study.

Supplementary Material

Publication History

Received: 10 February 2021

Accepted: 28 June 2021

Publication Date:
30 June 2021 (online)

© 2021. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany