European Heart Journal Advance Access originally published online on September 5, 2006
European Heart Journal 2006 27(19):2370; doi:10.1093/eurheartj/ehl241
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Stroke prophylaxis in atrial fibrillation
Manchester Medical Society
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The fact that patients aged >80 had clearly reduced chances of getting the recommended warfarin treatment even in the absence of contraindications1 is a reflection of the distrust that some clinicians have of the validity of use of low-intensity adjusted-dose warfarin2 for prophylaxis against embolic stroke in non-valvular atrial fibrillation (NVAF). Some of this mistrust may stem from the concomitant use of aspirin in the BAATAF study and from the fact that the target international normalized ratio (INR) of 1.5–2.7 was only an extrapolation from the parameter in use at the time, namely the prothrombin time ratio.2 Notwithstanding those reservations, the results of BAATAF were impressive, especially when compared with other stroke preventive treatments in NVAF.3 In a pairwise comparison of eight antithrombotic regimes vs. placebo, adjusted low-dose warfarin (LDW), adjusted standard dose warfarin, and ximelagatran, respectively, achieved the distinction of having not only the most favourable separation from the line of difference (i.e. the line that distinguishes treatments that are better than the comparator from treatments that are worse than the comparator), but also the narrowest confidence intervals.3 Furthermore, in a comparison of seven of those treatments with placebo, LDW emerged as being least likely to cause major or fatal bleeding episodes.3
The reluctance of some physicians to utilize LDW in patients aged >75, who are perceived to be at risk of major or fatal bleeding episodes but have, nevertheless, no contraindications to warfarinization is, however, not shared by the Task Force which recently revised the 2001 Guidelines for management of patients with atrial fibrillation. Their Class IIb recommendation was that ‘In patients aged 75 and older at increased risk of bleeding but without contraindications to oral anticoagulant therapy ... who are unable to tolerate anticoagulation ... at the standard intensity of INR 2.0–3.0, a lower INR target of 2.0 (range 1.6–2.5) may be considered’.4 In order to elevate that recommendation to the Class I level, a fully fledged randomized controlled trial of LDW vs. aspirin might be necessary, the target intensity of anticoagulation being an INR of 1.6–2.5 rather than the previously utilized prothrombin time ratio of 1.2–1.5 times the control value.
References
- Friberg L, Hammar N, Ringh M, Pettersson H, Rosenqvist M. (2006) Stroke prophylaxis in atrial fibrillation: who gets it and who does not? Eur Heart J 27:1954–1964.
[Abstract/Free Full Text] - The Boston Area Anticoagulation Trial for Atrial Fibrillation Investigators. (1990) The effect of low-dose warfarin on the risk of stroke in patients with no-rheumatic atrial fibrillation. N Engl J Med 323:1505–1511.[Abstract]
- Cooper NJ, Sutton AJ, Lu G, Khunti K. (2006) Mixed comparisons of stroke prevention treatments in individuals with nonrheumatic atrial fibrillation. Arch Int Med 166:1269–1275.
[Abstract/Free Full Text] - Task Force on Practice Guidelines: the European Society of Cardiology Committee for Practice Guidelines. (2006) ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation—executive summary. Eur Heart J 27:1979–2030.
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