Managing warfarin therapy in the community
Editor, – In the article `Managing warfarin therapy in the community' (Aust Prescr 2001;24:86-9) the authors state that there is good evidence that warfarin therapy is indicated for patients more than 50 years old who have non-valvular atrial fibrillation. This implies that almost all patients with non-valvular atrial fibrillation - including those with and without risk factors for stroke such as previous cerebrovascular events, structural heart disease, significant left ventricular systolic dysfunction, hypertension, left ventricular hypertrophy and diabetes - warrant anticoagulation with warfarin. The Framingham experience1 would suggest that only about 5% of all patients with non-valvular atrial fibrillation are less than 50 years old.
The American College of Chest Physicians Consensus Conference on anti-thrombotic therapy2 suggests that there is no need to consider warfarin in patients under the age of 65 years in the absence of risk factors for stroke. There is uncertainty about the risk faced by those with non-valvular atrial fibrillation including women up to the age of 75 years and men of any age. The 65-75 year age range includes a substantial proportion (approximately20%) of the patients with non-valvular atrial fibrillation.
More recent data from a study3 of more than 1700American Medicare beneficiaries (aged 65-95 years and clearly a sicker population than patients in previous anticoagulant trials) supported the view that in the absence of risk factors anticoagulant therapy could not be strongly recommended before the age of 75 years in either males or females.
It is therefore important for the clinician to try and assess the benefits of anticoagulation based on the risk of ischaemic and especially disabling stroke in the patient with non-valvular atrial fibrillation. Unfortunately debate on the age factor is undermined by the difficulties of managing warfarin in practice and by the lack of prospective trial data on patients randomly anticoagulated according to age cohorts.
- Brand FN, Abbott RD, Wolf PA. Characteristics and prognosis of lone atrial fibrillation. 30-year follow-up in the Framingham Study. JAMA 1985;254:3449-53.2. Albers GW, Dalen JE, Laupacis A, Manning WJ, Petersen P, Singer DE. Antithrombotic therapy in atrial fibrillation. Chest 2001;119 (1Suppl):194S-206S. 3. Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA 2001;285:2864-70. .
- Albers GW, Dalen JE, Petersen P. Antithrombotic therapy in atrial fibrillation. Chest 2001;119 (1 Suppl):194S-206S. 2. Levine MN, Raskob G, Landefeld S, Kearon C. Hemorrhagic complications of anticoagulant treatment. Chest 2001;119(Suppl): 108S-21S. .