Comparative effectiveness of NOAC vs VKA in patients representing common clinical challenges: results from the GARFIELD-AF registry
Authors: Virdone S , Himmelreich J.C.L , Pieper K.S , Camm A.J , Bassand J.-P , Fox K.A.A , Fitzmaurice D.A , Goldhaber S.Z , Goto S , Haas S , Kayani G , Misselwitz F , Turpie A.G.G , Verheugt F.W.A , Kakkar A.K ,   GARFIELD-AF Investigators
Published: October 2021

Abstract

Introduction
Large phase III trials of non-valvular atrial fibrillation (AF) patients have shown a favourable risk-to-benefit ratio with Non-Vitamin K antagonist oral anticoagulants (NOAC) compared to Vitamin K antagonists (VKA). Although the results of these trials are directly applicable to many AF patients, important subsets of patients were under-represented. Thus, there remains uncertainty about the safety and effectiveness of NOAC therapy in common challenging scenarios.

Purpose
The main purpose of this study is to quantify and compare the impact of NOAC vs VKA in settings where clinical uncertainty still exists and represents a considerable proportion of AF patients in clinical practice.

Methods
The analysis was conducted in patients enrolled in the largest AF multinational prospective registry (the Global Anticoagulant Registry in the FIELD–Atrial Fibrillation, GARFIELD-AF). We evaluated the effectiveness and safety of NOAC compared to VKA in three groups of patients representing common clinical challenges (CCC): 1) elderly patients (i.e. age ≥75), 2) increased bleeding risk (i.e. HAS-BLED ≥3 or prior bleeding), and 3) renal impairment (i.e. CKD stages II to IV).
We applied a propensity score using an overlap weighting scheme to obtain unbiased estimates of the treatment effect within each CCC group. Weights were applied to Cox proportional hazards models to estimate the effects of the NOAC vs VKA comparison on the occurrence of death, non-haemorrhagic stroke/SE and major bleeding within 2 years of enrolment.

Results
Comparative effectiveness of NOAC vs VKA was assessed in 8607 elderly patients, 1711 with increased bleeding risk, and 4460 with renal impairment.
The proportion of anticoagulated patients was low in patients with increased bleeding risk (59%), while in the other two CCC groups the corresponding proportion was close to the one in the overall population (72%).
Among anticoagulated patients, NOAC were prescribed to 50–55% of patients in the CCC groups. Patients with a high risk of bleeding and impaired kidney function were less likely to be prescribed NOAC instead of VKA compared with the overall anticoagulated population (−5.4% and −4.7%, respectively).
Propensity-weighted hazard ratios for all-cause mortality favored NOAC (vs VKA) in all three CCC groups: 0.86 (95% CI: 0.74–0.99) for elderly patients, 0.73 (0.53–1.00) for patients with increased bleeding risk, and 0.80 (0.65–0.98) for patients with renal impairment (Figure).

Conclusion
In the selected common challenging scenarios of AF patients, there were significant mortality reductions in favor of NOACs compared to VKAs. These observations suggest that NOACs are safe and effective in patients who are elderly, at increased bleeding risk, or renally impaired.

Funding Acknowledgement
Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This study was supported by an unrestricted research grant from Bayer AG, Berlin, Germany, to TRI, London, UK, which sponsors the GARFIELD-AF registry. The work is supported by KANTOR CHARITABLE FOUNDATION for the Kantor-Kakkar Global Centre for Thrombosis Science.