Stroke risk in atrial fibrillation patients on warfarin

Daniela Poli; Emilia Antonucci; Elisa Grifoni; Rosanna Abbate; Gian Franco Gensini; Domenico Prisco

doi:10.1160/TH08-09-0592

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2009; 101(02): 367-372
DOI: 10.1160/TH08-09-0592

Cardiovascular Biology and Cell Signalling

Schattauer GmbH

Stroke risk in atrial fibrillation patients on warfarin

Predictive ability of risk stratification schemes for primary and secondary prevention

Authors

Daniela Poli

¹Department of Medical and Surgical Critical Care, University of Florence and Department of Heart and Vessels, Thrombosis Centre, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy
Emilia Antonucci

¹Department of Medical and Surgical Critical Care, University of Florence and Department of Heart and Vessels, Thrombosis Centre, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy
Elisa Grifoni

¹Department of Medical and Surgical Critical Care, University of Florence and Department of Heart and Vessels, Thrombosis Centre, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy
Rosanna Abbate

¹Department of Medical and Surgical Critical Care, University of Florence and Department of Heart and Vessels, Thrombosis Centre, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy
Gian Franco Gensini

²Centro S. Maria agli Ulivi, Fondazione Don Carlo Gnocchi Onlus IRCCS, Impruneta, Florence, Italy
Domenico Prisco

¹Department of Medical and Surgical Critical Care, University of Florence and Department of Heart and Vessels, Thrombosis Centre, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy

Abstract

Summary

Atrial fibrillation (AF) patients are widely heterogeneous in terms of ischaemic stroke risk, and several risk stratification schemes have been developed. We performed a prospective study on 662 AF patients on long-term oral anticoagulant therapy (OAT), evaluating the agreement among the different schemes and their correlation with adverse events recorded during follow-up. Patients at low risk were similarly distributed among the different models. Instead, patients classed at moderate risk were 49.2% by CHADS2 score, 27.6% by NICE and 2.3% by ACCP. As a consequence patients classed at high risk were 46.1% by CHADS2, 69.8% by NICE and 95.3% by ACCP. CHADS2 and NICE scores were associated to the best predictive accuracy. A separate analysis was performed for patients on treatment for secondary prevention, and we observed that they were included in high risk groups by all models, except for 14 patients (6.3%) classed at moderate risk by CHADS2 even though these patients are at very high risk and the use of aspirin could be unsafe for them. During follow-up 32 major bleeding (1.35 per 100 patient/years) and 39 thrombotic events (1.64 per 100 patient/ years) were observed. Among patients on OAT for secondary prevention, both bleeding and thrombotic events mostly occurred in high-risk patients. Even if the absolute rate of adverse events is low, this finding seems to confirm the high stroke risk of this group of patients. For patients on secondary prevention there is no need for further stratification and warfarin should be the treatment of choice.

Keywords

Atrial fibrillation - stroke - warfarin - oral anticoagulants - prevention

Full Text

References

References
1 Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med 2007; 146: 857-867.
2 Gage BF, van Walraven C, Pearce L. et al. Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin. Circulation 2004; 110: 2287-2292.
3 Atrial Fibrillation Investigators.. Risk factors for Stroke and efficacy of antithrombotic therapy in atrial fibrillation. Arch Intern Med 1994; 154: 1449-1457.
4 Gage BF, Waterman AD, Shannon W. et al. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. J Am Med Assoc 2001; 285: 2864-2870.
5 Albers GW, Dalen JE, Laupacis A. et al. Antithrombotic therapy in atrial fibrillation. Chest 2001; 119: 194S-206S.
6 Singer DE, Albers GW, Dalen JE. et al. Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126: 429S-456S.
7 National collaborating centre for chronic conditions.. Atrial fibrillation: National Clinical Guideline for management in primary and secondary care. London: Royal College of Physicians; 2006. Available at: htpp://www.nice.org.uk/guidance/CG36.
8 Baruch L, Gage BF, Horrow J. et al. Can patients at elevated risk of stroke treated with anticoagulants be further risk stratified?. Stroke 2007; 38: 2459-2463.
9 Stroke Risk in Atrial Fibrillation Working Group.. Comparison of 12 risk stratification schemes to predict stroke in patients with nonvalvular atrial fibrillation. Stroke 2008; 39: 1901-1910.
10 Iliceto S. A guide to Oral Anticoagulant Therapy: Recommendation of Italian Federation of Anticoagulation Clinics. Haematologica 2003; 88 (Suppl. 02) 1.
11 Rosendaal FR, Cannegieter SC, van der Meer FJM. et al. A method to determine the optimal intensity of oral anticoagulant therapy. Thromb Haemost 1993; 69: 236-239.
12 Report of the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 2002; 26: S5-S20.
13 Fuster V, Rydén LE, Cannom DS. et al. ACC/AHA/ ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation 2006; 114: e257-354.
14 Palareti G, Leali N, Coccheri S. et al. Bleeding complications of oral anticoagulant treatment: an inception-cohort, prospective collaborative study (IS-COAT). Italian Study on Complications of Oral Anticoagulant Therapy. Lancet 1996; 348: 423-428.
15 Taggar JS, Watson T, Lip GY. Can patients with atrial fibrillation be optimally risk stratified for stroke and thromboembolism?. Stroke 2008; 39: e24-25.
16 Wang TJ, Massaro JM, Levy D. et al. A risk score for predicting stroke or death in individuals with new-onset atrial fibrillation in the community: the Framing-ham Heart Study. J Am Med Assoc 2003; 290: 1049-1056.
17 van Walraven C, Hart RG, Wells GA. et al. A clinical prediction rule to identify patients with atrial fibrillation and a low risk for stroke while taking aspirin. Arch Intern Med 2003; 163: 936-943.
18 Rothman KJ, Greenland S. Modern Epidemiology. 2^nd ed. Philadelphia: Lippincott-Raven; 1998
19 Harrell Jr FE, Lee KL, Mark DB. Multivariable prognostic models: issues in developing models, evaluating assumptions and adequacy, and measuring and reducing errors. Stat Med 1996; 15: 361-387.
20 Fang MC, Go AS, Chang Y. et al. ATRIA Study Group.. Comparison of risk stratification schemes to predict thromboembolism in people with nonvalvular atrial fibrillation. J Am Coll Cardiol 2008; 51: 810-815.
21 Hughes M, Lip GY. Guideline Development Group, National Clinical Guideline for Management of Atrial Fibrillation in Primary and Secondary Care, National Institute for Health and Clinical Excellence. Stroke and thromboembolism in atrial fibrillation: a systematic review of stroke risk factors, risk stratification schema and cost effectiveness data. Thromb Haemost 2008; 99: 295-304.
22 Lip GY. Paroxysmal atrial fibrillation, stroke risk and thromboprophylaxis. Thromb Haemost 2008; 100: 11-13.
23 Mant J, Hobbs FD, Fletcher K. et al. Warfarin versus aspirin for stroke prevention in an elderly community population with atrial fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial. Lancet 2007; 370: 493-503.
24 Nieuwlaat R, Capucci A, Lip GY. et al. Euro Heart Survey Investigators.. Antithrombotic treatment in real-life atrial fibrillation patients: a report from the Euro Heart Survey on Atrial Fibrillation. Eur Heart J 2006; 27: 3018-3026.
25 Mant JW. Pro: ‘Warfarin should be the drug of choice for thromboprophylaxis in elderly patients with atrial fibrillation‘. Why warfarin should really be the drug of choice for stroke prevention in elderly patients with atrial fibrillation. Thromb Haemost 2008; 100: 14-15.
26 Hylek EM. Contra: ‘Warfarin should be the drug of choice for thromboprophylaxis in elderly patients with atrial fibrillation‘. Caveats regarding use of oral anticoagulant therapy among elderly patients with atrial fibrillation. Thromb Haemost 2008; 100: 16-17.