NOAC or Warfarin for Atrial Fibrillation: Does Time in Therapeutic Range Matter?

Atrial fibrillation (AF) is the commonest cardiac arrhythmia currently affecting 1-2% of the general population, with stroke being one of its most fearsome complications. Dose-adjusted warfarin is an established treatment for reduction of thromboembolic risk but mandates dietary restrictions and need for routine blood monitoring. Novel oral anticoagulants (Dabigatran - patent: US20110082299A1, manufactured by Boehringer Ingelheim; Rivaroxaban - patent: US20150175590A1, manufactured by Bayer; Apixaban - patent: US20140335178A1, manufactured jointly by Pfizer and Bristol-Myers Squibb; Edoxaban - patent: WO2013026553A1, manufactured by Daiichi Sankyo) have recently been introduced that might provide at least equal reduction in thromboembolic risk to patients; negating the need for dietary restrictions and routine blood tests. The most recent National Institute of Health and Care Excellence, UK guidelines from August 2014 suggest consideration of one of the novel oral anticoagulants if the time in therapeutic range is less than 65%. In this study, the evidence for four novel oral anticoagulants is reviewed and the anticoagulation success with warfarin with atrial fibrillation and mechanical heart valves assessed in a large UK District General Hospital. Fifty-eight patients were identified with mechanical heart valve and 2737 patients with atrial fibrillation. Patients with atrial fibrillation had a significantly better TTR when compared with the patients included in the NOAC trials. Our results were similar with the Auricula registry. However, 25% of patients had TTR<65% and they would need to be considered for NOACs. Our data suggest that the degree of benefit seen in the NOAC trials might not be expected in our cohort of patients with atrial fibrillation. Interestingly, our patients with atrial fibrillation had a much better mean TTR of 76.4% and required less INR tests (12/year) compared to patients with mechanical heart valve who had a mean TTR of 61.4% and required more INR tests (26/year).