May 1, 2023EP EuropaceOpen Access

Non-vitamin K antagonist oral anticoagulants in atrial fibrillation patients without previous oral anticoagulants or stable under warfarin: a nationwide cohort study

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Why the study?

Investigations of NOACs in AF patients not taking any OACs or remaining stable on warfarin were limited.

Does initiation of NOACs reduce the risk of ischaemic stroke and bleeding in atrial fibrillation patients who were previously stable without oral anticoagulants or on warfarin?

Structured PICO

Does initiation of NOACs reduce the risk of ischaemic stroke and bleeding in atrial fibrillation patients who were previously stable without oral anticoagulants or on warfarin?

Population

54,803 atrial fibrillation patients who did not experience an ischaemic stroke or intra-cranial haemorrhage (ICH) for years after AF was diagnosed, including 32,917 patients who did not receive OACs and 8,007 patients who continuously received warfarin.

Intervention

Non-vitamin K antagonist oral anticoagulants (NOACs)

Comparator

No oral anticoagulants (non-OAC) or continuous warfarin

Outcome

Ischaemic strokehard clinical

Initiating NOACs improves clinical outcomes even in atrial fibrillation patients who have remained free of stroke or bleeding for years without anticoagulation or while stable on warfarin.

Implication

May support switching stable warfarin patients to NOACs; leaves open randomized confirmation of net benefit.

Abstract

AIMS: Investigations on non-VKA oral anticoagulants (NOACs) for atrial fibrillation (AF) patients without taking any oral anticoagulants (OACs) or staying well on warfarin were limited. We aimed to investigate the associations between stroke prevention strategies and clinical outcomes among AF patients who were previously well without taking any OACs or stayed well on warfarin for years. METHODS AND RESULTS: The retrospective analysis included a total of 54 803 AF patients who did not experience an ischaemic stroke or intra-cranial haemorrhage (ICH) for years after AF was diagnosed. Among these patients, 32 917 patients who did not receive OACs were defined as the 'original non-OAC cohort' (group 1), and 8007 patients who continuously received warfarin were defined as the 'original warfarin cohort' (group 2). In group 1, compared to non-OAC, warfarin showed no significant difference in ischaemic stroke (aHR 0.979, 95%CI 0.863-1.110, P = 0.137) while those initiated NOACs were associated with lower risk (aHR 0.867, 95%CI 0.786-0.956, P = 0.043). When compared to warfarin, the composite of 'ischaemic stroke or ICH' and 'ischaemic stroke or major bleeding' was significantly lower in the NOAC initiator with an aHR of 0.927 (95%CI 0.865-0.994; P = 0.042) and 0.912 (95%CI 0.837-0.994; P < 0.001), respectively. In group 2, when compared to warfarin, those shifted to NOACs were associated with a lower risk of ischaemic stroke (aHR 0.886, 95%CI 0.790-0.993, P = 0.002) and major bleeding (aHR 0.849, 95%CI 0.756-0.953, P < 0.001). CONCLUSIONS: The NOACs should be considered for AF patients who were previously well without taking OACs and those who were free of ischaemic stroke and ICH under warfarin for years.