We appreciate the response from Dr Trusler regarding our article on oral anticoagulation in atrial fibrillation (AF).1 He raises several interesting points. We are not aware of any publications extracting hemorrhagic stroke rates from ARISTOTLE, RELY, or ROCKET-AF by geographic location, nor what the differences in HAS-BLED risk criteria were at time of hemorrhagic stroke. We agree that the new oral anticoagulants likely have minimal to no advantage over well-controlled warfarin. We are aware of the subgroup analysis by Wallentin et al comparing the efficacy and safety of dabigatran to warfarin at different levels of international normalized ratio control.2 It was reassuring to see that warfarin had similar outcomes to 150 mg of dabigatran twice daily when the mean time in the therapeutic range (TTR) was 65.5% to 72.6% (hazard ratio 0.69, 95% CI 0.44 to 1.09), and when mean TTR was greater than 72.6% (hazard ratio 0.95, 95% CI 0.61 to 1.48). As mentioned in our article, the Canadian Agency for Drugs and Technologies in Health recommends the use of new oral anticoagulants only in patients who are unable to achieve adequate anticoagulation with warfarin.3 We also agree that there is need for better warfarin management.
The Canadian Agency for Drugs and Technologies in Health released a report on optimal warfarin management for the prevention of thromboembolic events in AF patients. The report included one study which examined TTR in AF patients; the TTR increased from 46% in 1992 using cardiologist-based manual dosing to 81% in 2006 using computer-assisted dosing in the same practice.4 The report concluded by recommending a structured approach to warfarin therapy regardless of care setting. A computerized system for dosing warfarin might be a helpful tool; however, as Dr Trusler noted, not all centres can afford to incorporate one. An ideal structured approach for warfarin management would include ongoing patient education, follow-up, and dosing tools. Unfortunately, there likely is no one-size-fits-all solution owing to the variety of practice settings, provincial guidelines, local dosing nomograms, etc.
We appreciate the comments from Dr Trusler, which raise several interesting discussion points.
Footnotes
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Competing interests
None declared
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