Long-term PT-INR levels and the clinical events in the patients with non-valvular atrial fibrillation: A special reference to low-intensity warfarin therapy

BackgroundAnticoagulation therapy is essential in atrial fibrillation (AF), and in Japan, less intense control is popular.PurposeTo assess the efficacy and safety with a special reference to low intensity warfarin therapy.Subjects and methodsIn 488 out of 508 patients with non-valvular AF, prothrombin time-international normalized ratio (PT-INR) was kept at 1.6–2.59, and they were followed for 49.5 months: 2098 person-years. The mean age was 73.7 ± 9.9 years and 62% were male. The patients were divided by age: ≥70 years and <70 years, and by the intensity of warfarin therapy: PT-INR at 1.6–1.99 and at 2.0–2.59, respectively. The clinical data and event rates, ischemic stroke and major bleeding, were compared among the subgroups.ResultsHeart failure, previous stroke, and higher CHADS2 score were more often reported in patients ≥70 years while males were involved more often as younger patients. A total of 166 of 339 patients ≥70 years and 69 of 149 patients <70 years belonged to the low intensity group.Ischemic stroke and major bleeding occurred in 1.47%/year and 1.27%/year, respectively but there was no difference between the two age groups and between the two intensities of warfarin therapy. Time in therapeutic range was a predictor for ischemic stroke. A fall of PT-INR to <1.6 was found in 41.9% with ischemic stroke and a rise >2.61 in 40.0% with major bleeding at the time of the events. Blunt trauma and concomitant use of antiplatelets were risks for intracranial hemorrhage in the patients ≥70 years.ConclusionsThe event rates were similar between the low- (1.6–1.99) and high- (2.0–2.59) intensity warfarin therapy groups in aged patients: <70 years and ≥70 years. Time in therapeutic range and a transient fall or rise in PT-INR were risks for clinical events. Blunt head trauma and concomitant use of antiplatelets were risks for intracranial hemorrhage.