October 23, 2018Open Access

Frequency of atrial thrombus formation in patients with atrial fibrillation under treatment with non-vitamin K oral anticoagulants in comparison to vitamin K antagonists: a systematic review and meta-analysis

Q: What is the clinical evidence from this study?

Study design: Meta-Analysis. Population: Non-valvular atrial fibrillation (n=2397). Intervention: Non-vitamin K oral anticoagulants (NOACs) vs. Vitamin K antagonists (VKAs). Primary outcome: Frequency of left atrium/left atrial appendage (LA/LAA) thrombus formation (OR 1.14, 95% CI 0.97-1.65, p=0.48).

Key Result

Non-vitamin K oral anticoagulants demonstrated a similar frequency of left atrial/left atrial appendage thrombus formation compared to vitamin K antagonists in patients with atrial fibrillation (OR 1.14).

Study Design

Type

Meta-Analysis (n=2,397)

PICO

Population

Non-valvular atrial fibrillation (n=2,397)

Intervention / Comparator

Non-vitamin K oral anticoagulants (NOACs) vs Vitamin K antagonists (VKAs)

Primary Outcome

Frequency of left atrium/left atrial appendage (LA/LAA) thrombus formation — OR 1.14 (0.97-1.65), p=0.48

Main Result

Effect estimate: OR 1.14 (95% CI 0.97-1.65)

Absolute Event Rate: 5% vs 5%

p-value: p=0.48

Limitations

The four trials included differed with respect to protocol, inclusion and exclusion criteria, and study population.
Time in therapeutic range (TTR) was only available in two of the included trials.
The small number of studies made a reliable assessment of heterogeneity and publication bias virtually impossible.
The weight of included studies diverges considerably, with the majority involving the ENSURE-AF study.
The duration of anticoagulant treatment prior to TEE in most included trials is unknown.
An unknown proportion of patients in the original studies did not receive sufficient anticoagulation for at least 3 weeks prior to TEE examination.

Abstract

To assess the frequency of left atrium/left atrial appendage (LA/LAA) thrombus under treatment with non-vitamin K oral anticoagulants (NOACs) in comparison with vitamin K antagonists (VKAs) in patients with non-valvular atrial fibrillation (AF). PubMed, Web of Science™, EMBASE and the Cochrane Library databases were searched for studies comparing NOACs with VKAs in AF patients who underwent diagnostic transoesophageal echocardiography (TEE). A total of four trials were considered eligible and were included in the meta-analysis. Four RCTs comprising n = 2397 AF patients (NOACs: n = 1412, VKAs: n = 985) were included in the meta-analysis. The frequency of LA/LAA thrombus formation under treatment with NOACs was similar to VKAs odds ratio (OR) 1.14, 95% confidence intervals (95% CIs) 0.97–1.65, p = 0.48. Both treatment groups revealed an approximately 5% frequency of thrombus formation, although a precise calculation is not possible due to Simpson paradox. Indications of heterogeneity between the included trials were not found (χ2 test p = 0.99, I2 = 0%). The findings of this meta-analysis suggest that NOACs are similar to VKAs regarding the frequency of LA/LAA thrombus in patients with AF. An unknown number of patients in the original studies did not receive sufficient anticoagulation for at least 3 weeks prior to TEE examination, and therefore the present results should be interpreted with caution. Systematic review registration— http://www.crd.york.ac.uk/PROSPERO . Unique identifier: PROSPERO CRD42017059293.

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