Attitudes of Japanese Cardiologists Toward Anticoagulation for Nonvalvular Atrial Fibrillation and Reasons for Its Underuse

Abstract

andomized clinical trials clearly show that adjusted dosage of warfarin decreases embolic episodes by two-thirds in patients with nonvalvular atrial fibrillation (NVAF), and that aspirin only does so to a modest extent. 1 Together with progressive accumulation of data supporting the efficacy of warfarin, its use has increased gradually, 2-7 but was still less than 50% even among patients with NVAF who were complicated with risk factors for embolism. 3,5,8 Previous clinical studies indicated that 50-60% of patients with NVAF did not have contraindications to warfarin use, 4 and a recent guideline recommended appropriate antithrombotic therapy and intensities of anticoagulation with warfarin according to the age and other clinical characteristics of patients with NVAF. 9 There are clear ethnic differences in the perceptions of atrial fibrillation (AF) and anticoagulation therapy among patients living in England, 10 and possible ethnic differences in the incidence of stroke. 11 Therefore, there could be difCirculation Journal Vol.68, May 2004 ferences between Japan and the USA in cardiologists' attitude toward antithrombotic therapy in patients with NVAF. In the early 90 s Japanese cardiologists used warfarin in less than 20% of patients with AF, 12,13 so the aim of the present study was to determine current attitudes toward warfarin use, the proportion of adherence to the guideline for antithrombotic therapy and reasons for non-use of warfarin in patients with NVAF. Methods Study SubjectsWe started a prospective, cooperative study from 1999 to determine the clinical efficacy of measuring hemostatic markers to identify patients with NVAF who would be at increased risk for embolic complication. 14 The design of the study was approved by the ethics committee of each university hospital. Patients with NVAF treated in 1999 at 5 tertiary, university hospitals were subjects of the present study. A total of 509 patients (66.6±10.3 years old, 330 men and 179 women) with NVAF were enrolled in the study after giving informed consent. 14 Baseline clinical characteristics, including diabetes mellitus, hypertension, New York Heart Association functional status, prior cerebral infarction (CI) or transient ischemic attack (TIA), status of antithrombotic therapy, and type of AF, were determined. The selection of antithrombotic drugs was left to the treating cardiologist's decision. Intensity of anticoagulation with warfarin expressed as the international normalized ratio (INR) of prothrombin time was determined at the time

Under-use of Warfarin for Patients with Non-valvular Atrial Fibrillation in Japan

“…In contrast, experience of preventive therapy in patients with embolism due to AF was associated with positive attitude. An advanced age and a risk of bleeding complications of patients were deterrent factors to non-use of warfarin as seen in a current study in Japan (10).…”

“…This suggests that adherence to the guideline (11) for the prevention of embolic events in patients with NVAF is currently greatly improved among cardiologists in Japan. In that study (10), approximately one-third of 509 patients had at least one clinical risk factor for embolism but did not receive warfarin. Contraindications were found in only one quarter and paroxysmal nature of NVAF seemed a possible reason for the non-use of warfarin in nearly one-half of the patients with risk factors but not receiving warfarin.…”

“…Taken together, warfarin is not used widely for treatment of NVAF patients having clinical risk factors even at tertiary, university hospitals in Japan. The reasons for not using warfarin seemed inappropriate in most of cases (10).…”

“…For elderly patients warfarin use was quite low (<10%) (8). A recent survey (10) in Japan disclosed that 50-60 % of patients with NVAF who had at least one clinical risk factor for embolism received warfarin. This suggests that adherence to the guideline (11) for the prevention of embolic events in patients with NVAF is currently greatly improved among cardiologists in Japan.…”

Determinants of Warfarin Use and International Normalized Ratio Levels in Atrial Fibrillation Patients in Japan - Subanalysis of the J-RHYTHM Registry -

“…3 In a previous observational study carried out in Japan, it was found that the paroxysmal type of AF is associated with the non-use of warfarin in patients with non-valvular AF and a CHADS2 score ≥1. 5 No detailed analysis of the non-use of warfarin in Japan, however, has been performed.…”