What is the clinical evidence from this study?

Study design: Observational. Intervention: Anatomical evaluation vs. Left vs Right atrial appendages. Primary outcome: Pectinate muscle architecture, size, and density (p=<0.001).

What does this research mean for the field?

The right atrial appendage is significantly larger but has lower pectinate muscle density than the left atrial appendage, and these distinct anatomical variations can be effectively visualized using clinical imaging modalities such as angio-CT and transesophageal echocardiography. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This study aims to quantify variations in muscle architecture of atrial appendages and evaluate imaging techniques.

June 7, 2026Open Access

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Clinical Anatomy of the Left and Right Atrial Appendages in Humans: Comparative and Developmental Perspective

Q: What are the key findings of this study?

Right atrial appendages were larger (p < 0.001) but showed lower muscle density (p = 0.007) than left atrial appendages, with transesophageal echocardiography excelling for visualization.

Q: What does this research mean for the field?

The right atrial appendage is significantly larger but has lower pectinate muscle density than the left atrial appendage, and these distinct anatomical variations can be effectively visualized using clinical imaging modalities such as angio-CT and transesophageal echocardiography. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

This study aims to quantify variations in muscle architecture of atrial appendages and evaluate imaging techniques.

MLMarkéta LexováCharles University CNC NeradilovaCharles University JKJan KovandaCharles University

Key Result

Right atrial appendages were larger (p < 0.001) but showed lower muscle density (p = 0.007) than left atrial appendages, with transesophageal echocardiography excelling for visualization.

Key Points

This study aims to quantify variations in muscle architecture of atrial appendages and evaluate imaging techniques.
Examined 153 cadaveric donor hearts using gross dissection and clinical imaging modalities.
Utilized histology, ex vivo micro-CT, and in vivo imaging (CT angiography, MRI, echocardiography).
Classified left atrial appendage and right atrial appendage morphologies.
Left atrial appendage morphologies included chicken-wing (41%) and cactus (23%) types.
Right atrial appendages were larger in size (p < 0.001) but lower in muscle density (p = 0.007).
Angio-CT demonstrated superior detail in LAA imaging compared to other modalities.

Study Design

Type

Observational (n=153)

Structured PICO

Population

153 cadaveric donor hearts evaluated for macroscopic variations in pectinate muscle architecture using gross dissection, micro-CT, histology, and clinical imaging.

Exposure

Gross dissection, ex vivo micro-CT, histology, and in vivo clinical imaging (CT angiography, MRI, and transthoracic/transesophageal echocardiography)

Outcome

Macroscopic variations in pectinate muscle architecture in human atrial appendages and evaluation of their visualization using clinical imaging modalitiessurrogate

Detailed anatomical characterization of left and right atrial appendages provides insights for clinical imaging, catheter ablation, pacing, and stroke risk stratification.

Main Result

p-value: p=<0.001

Abstract

Human atrial chambers derive from distinct embryonic anlagens, the original embryonic atria gradually transforming into the so-called auricles, or atrial appendages. This study quantifies macroscopic variations in pectinate muscle architecture in human atrial appendages and evaluates their visualization using clinical imaging modalities. We examined 153 cadaveric donor hearts (103 specified sex: 61 female, 42 male; plus 50 unspecified), employing gross dissection, ex vivo micro-CT, histology, and in vivo clinical imaging (CT angiography, MRI, and transthoracic/transesophageal echocardiography). Left atrial appendage (LAA) morphologies (Wang classification) comprised chicken-wing (41%), cactus (23%), cauliflower (22%), and windsock (14%) types, with 11 ± 4 (mean ± SD) main pectinate muscles (length: 47 ± 16 mm). Right atrial appendage (RAA) pectinate muscle arrangements (Loukas classification) were dominated by type IV (41%), followed by types I/II (22%/20%), with 17 ± 4 muscles (length: 75 ± 17 mm); the RAAs were larger (p < 0.001) but showed lower muscle density (p = 0.007) than the LAAs. All modalities resolved main pectinate bundles, with angio-CT providing superior LAA detail; transesophageal echocardiography excelled for both sides. Precise atrial appendage morphology informs catheter ablation, pacing, and stroke risk stratification, bridging anatomical and clinical perspectives.

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Clinical Anatomy of the Left and Right Atrial Appendages in Humans: Comparative and Developmental Perspective

Key Result

Key Points

Study Design

Structured PICO

Main Result

Abstract

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