Quality of vitamin K antagonist oral anticoagulation in 322 patients with atrial fibrillation - real-life data from a survey in Eastern Switzerland.

Micha T Maeder ,Sanja Bogdanović ,Marius König,Werner Eugster,Tabea König,Peter Ammann,Jürg H Beer ,I Schneider ,Hans Rickli

doi:10.4414/smw.2017.14503

Abstract

To better appreciate the role of the non-vitamin K oral anticoagulants (NOACs) for patients with non-valvular atrial fibrillation in Switzerland we aimed to assess the quality of vitamin K antagonist (VKA) anticoagulation in daily practice. In a cross-sectional study, clinically stable patients on VKA treatment for non-valvular atrial fibrillation for at least 6 months, documentation of international normalised ratio (INR) values for at least 3 months and with at least two INR values were included. The percentage of INR values within the therapeutic range of 2.0 to 3.0 and the time in therapeutic range (TTR; Rosendaal method) and predictors for these measures of VKA anticoagulation quality were assessed. We studied 332 patients (62% male, mean age 74 ± 9 years) with median (interquartile range) CHA2DS2Vasc and HAS-BLED scores of 4 (3-5) and 3 (2-4) points. The median number of INR values per patient was 8 (5-14), and the average interval between INR measurements was 20 (13-27) days. The percentage of INR values between 2.0 and 3.0 was 67% (50-83%). The median TTR was 69% (51-89%), and TTR ≥65% was found in 202 (61%) patients. Independent predictors of ≥80% INR values between 2.0 and 3.0 included a longer interval between INR measurements and the non-use of spironolactone. The non-use of amiodarone and spironolactone and a longer interval between INR measurements were the only independent predictors of a TTR ≥65%. The quality of VKA anticoagulation in Switzerland is highly variable. Importantly, only 60% of patients achieve a TTR ≥65%, which is currently considered to be the minimal acceptable TTR required for VKA therapy. There are few clinical predictors of a good VKA anticoagulation quality. These data may represent a novel basis for decision making regarding the choice of anticoagulation for atrial fibrillation in Switzerland.

Highlights

A key clinical question to address in every patient with atrial fibrillation (AF) is whether long-term oral anticoagulation (OAC) is required, and if yes, which type of OAC should be used
In studies showing comparable thromboembolic risks in AF patients treated with vitamin K antagonist (VKA) or non-vitamin K antagonist oral anticoagulants (NOACs), the mean therapeutic range (TTR) values were between 55 und 65% in the VKA-treated patients [2,3,4,5]
Gallen with VKA treatment for non-valvular AF for at least 6 months, documentation of international normalised ratio (INR) values over a period of at least 3 months with at least two INR values, and available INR booklet at the time of hospital admission were included between January 2011 and December 2014

Summary

Introduction

A key assumption underlying these recommendations is that an effective and safe mode of OAC is used. This can be achieved by use of either vitamin K antagonist (VKA) OAC with a high time in the therapeutic range (TTR) (i.e., an INR of 2.0–3.0) or non-vitamin K antagonist oral anticoagulants (NOACs) [1]. In practice a TTR in this range must be achieved to ensure that VKA therapy is likely to provide a similar thromboembolic risk reduction as NOACs. The Swedish national registry has revealed that a TTR of ≈75% is achievable [6], and that VKA therapy is very safe and effective under these circumstances [7]

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