Subgroups of anticoagulated patients with atrial fibrillation (AF) and atrial flutter (AFL) that have a high prevalence of left atrial (LA) thrombus may benefit from undergoing routine preprocedural transesophageal echocardiogram (TEE), according to study findings published in the Journal of the American College of Cardiology.

The presence of LA thrombus in patients with AF or AFL on guideline-directed anticoagulation, which is not well documented, may inform TEE use before cardioversion or catheter ablation, according to study researchers.

The purpose of this systematic review and meta-analysis was to evaluate LA thrombus prevalence of patients with AF/AFL who had been on continuous oral anticoagulation therapy for at least 3 weeks. Prevalence was assessed by oral anticoagulant type, TEE indication, AF pattern, and CHADS2 (congestive heart failure, hypertension, age >75 y, diabetes, and stroke)/CHA2DS2-VASc (congestive heart failure, hypertension, age >75 y, diabetes, stroke, vascular disease, age 65-74 y, and female sex) score to identify populations at clinically higher risk, in which TEE diagnostic yield may be greater.

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CENTRAL, EMBASE, and MEDLINE were systematically searched from inception to July 2020 with search terms including atrial fibrillation, left atrial thrombus, oral anticoagulation, transesophageal echocardiography, and their variations. Study researchers used random-effects models to perform meta-analyses.

Among 35 eligible studies, 14,653 patients were identified. The mean-weighted prevalence of LA thrombus was 2.73% (95% CI, 1.95-3.80), with high interstudy heterogeneity (I2=91%). Sensitivity analyses that excluded studies with a medium or higher risk for bias did not significantly impact prevalence (P >.05); however, excluding studies with small populations (defined as N<150) did modestly reduce LA thrombus prevalence to 2.40% (95% CI, 1.68-3.42; P =.048). In subgroup analyses, LA thrombus prevalence was similar for patients on anticoagulation with a vitamin K antagonist and those receiving direct oral anticoagulant therapy (2.80%; 95% CI, 1.86%-4.21% vs 3.12%; 95% CI, 1.92%-5.03%; P =.674).

Patients with nonparoxysmal AF had approximately 4 times higher LA thrombus prevalence than patients with paroxysmal AF (4.81%; 95% CI, 3.35-6.86 vs 1.03%; 95% CI, 0.52-2.03; P <.001). Patients undergoing cardioversion had a higher LA thrombus prevalence compared with those undergoing catheter ablation (5.55%; 95% CI, 3.15-9.58 vs 1.65%; 95% CI, 1.07-2.53; P <.001). When patients were stratified by CHADS2 or CHA2DS2-VASc scores, an increased LA thrombus prevalence was seen in those with higher risk scores (CHADS2 <1: 0.82%; 95% CI, 0.37-1.82 vs CHADS2 >2: 4.24%; 95% CI, 1.94-8.99; P <.001; CHA2DS2-VASc <2: 1.06%; 95% CI, 0.45-2.49 vs CHA2DS2-VASc >3: 6.31%; 95% CI, 3.72-10.49; P <.001). The exclusion of studies that were suspected to contain subtherapeutic populations did not meaningfully alter the authors’ findings.

The study researchers concluded, “In this systematic review and meta-analysis reporting on the prevalence of LA thrombus in patients with AF/AFL receiving a minimum of 3 weeks of anticoagulation, LA thrombus prevalence was approximately 3%. Nonparoxysmal AF and elevated CHADS2/CHA2DS2-VASc scores were associated with an increased prevalence of LA thrombus. TEE imaging in select patients at an elevated risk of LA thrombus, despite anticoagulation status, may be a reasonable approach to minimize the risk of thromboembolic complications following cardioversion or catheter ablation.”


Lurie A, Wang J, Hinnegan KJ, et al. Prevalence of left atrial thrombus in anticoagulated patients with atrial fibrillation. Published online June 15, 2021. J Am Coll Cardiol. doi:10.1016/j.jacc.2021.04.036