Key result
3D-CT identifies 4 distinct RAA morphologies associated with significant differences in appendage volume.
Why the study?
The introduction of atrial leadless pacemakers recommended for implantation at the base of the right atrial appendage (RAA) has made detailed assessment of RAA morphology and anatomical variations increasingly important.
Observational (n=144)
Right atrial appendage morphology can be classified via 3D-CT into four distinct types with significantly different volumes, providing anatomical insights for atrial leadless pacemaker implantation.
RAA morphology classification on 3D-CT may inform leadless pacemaker planning; leaves open effects on procedural outcomes.
Background With the introduction of atrial leadless pacemakers such as the AVEIR AR system, implantation at the base of the right atrial appendage (RAA) has been recommended because the apical region is relatively thin. Therefore, detailed assessment of RAA morphology and its anatomical variations has become increasingly important. Aim We aimed to characterize the morphology of the RAA and evaluate its anatomical variations using three-dimensional computed tomography (3D-CT). Methods We retrospectively analyzed 144 consecutive patients with atrial fibrillation who underwent contrast-enhanced 3D-CT prior to catheter ablation. RAA morphology, anatomical variations, and RAA volume were assessed, and the anatomical relationship between the RAA and left atrial appendages (LAA) was examined. Results Among 144 patients, RAA morphology was categorized into four distinct types (Figure): bicornuate (n=41, 28%), unicornuate (n=27, 19%), trapezoid (n=39, 27%), and tapered (n=37, 26%). The tapered type was defined by an anteroposterior diameter <40 mm at the RAA tip. The median RAA volume (IQR) for each type was 33.3 (28.0–45.7), 38.7 (33.4–48.0), 41.4 (33.0–48.4), and 26.7 (20.0–32.8) mL, respectively. RAA volume differed significantly among the four morphological types (one-way ANOVA, F=11.34, p<0.0001). The tapered type demonstrated the smallest RAA volume, whereas the unicornuate and trapezoid types exhibited larger volumes. A modest association between RAA and LAA morphology was observed (likelihood ratio χ²=18.6, p=0.029), whereas the Pearson chi-square test did not reach statistical significance (p=0.071). Conclusion RAA morphology can be classified into four distinct types, which are associated with significant differences in RAA volume. Although a modest association between RAA and LAA morphology was observed, the relationship appears clinically limited. These anatomical findings may provide useful insights into atrial leadless pacemaker implantation.RAA Morphological ClassificationRAA volume
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Ishimura et al. (2026) conducted an observational in Atrial fibrillation (n=144). 3D-CT morphological classification of the right atrial appendage (RAA) vs. Comparison across four RAA morphological types (bicornuate, unicornuate, trapezoid, tapered) was evaluated on Right atrial appendage (RAA) morphological classification and RAA volume (F=11.34, p=<0.0001).
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