International normalised ratio stability in patients aged 80 years and over taking warfarin for non-valvular atrial fibrillation

BackgroundA large proportion of the older population with non-valvular atrial fibrillation (NVAF) receive warfarin for stroke prevention, the safety and efficacy of which is affected by the time-in-therapeutic range (TTR). This has optimum effectiveness where the mean TTR is ≥70%, whilst no survival benefit is conferred if TTR is <40%.ObjectiveTo assess the TTR of patients aged 80 and over with NVAF on warfarin.MethodsA retrospective analysis was performed on patients that had utilised an intermediate care service at a London hospital over one year. Patients were on warfarin for NVAF, aged ≥80 with a minimum of six continuous months of results. The therapeutic range was defined as an international normalised ratio of ≥2 and ≤3 and the TTR was calculated for each patient.Results118 patients were identified with a mean age of 86.1 (80-107). 9 (7.6%) patients were within the therapeutic range for ≥70% of the time and 31 (26.3%) patients were within the therapeutic range for <40% of the time. The mean TTR was 47.5% (standard deviation 14.4%, range 12.5-81.8%). Those with a hospital admission had a significantly lower mean TTR versus those without an admission (p-value = 0.013).ConclusionThe TTR is extremely low in this cohort of patients aged 80 years and older who are on warfarin for NVAF. This exposes patients to significant risks of both bleeding and ischaemic stroke. Assessment of INR control should be carried out and consideration should be given as to whether novel oral anticoagulants should be more widely used in this population.