A rare case of congenital absence of left atrial appendage diagnosed by multimodal imaging

Abstract

Congenital absence of the left atrial appendage (LAA) is an exceptionally rare cardiac anomaly. We reported a patient in his 60s with symptomatic persistent atrial fibrillation (AF) and no history of cardiac surgery or other diseases. During preprocedural evaluation for AF cardioversion, transesophageal echocardiography and cardiac computed tomography revealed a complete absence of the LAA. The patient was managed with regular anticoagulation therapy and maintained in sinus rhythm, without recurrence or related complications during a 1-year follow-up.

Introduction

The left atrial appendage (LAA) originates from the primordial left atrium (LA) during early cardiac development, primarily through the incorporation of the pulmonary veins and their branch. ¹ In patients with atrial fibrillation (AF), transesophageal echocardiography (TEE) is commonly performed before radiofrequency ablation or LAA closure to evaluate thrombus formation. ² Congenital absence of LAA is exceedingly uncommon, and its physiological consequences remain uncertain. The prevalence of LAA absence among AF patients undergoing closure procedures has been reported to be approximately 1.2%. ³ Despite these data, the exact prevalence of LAA remains unclear and requires further large-scale epidemiological studies. ⁴ We describe a rare case of a congenitally absent LAA detected incidentally during pre-ablation evaluation in a routine TEE examination.

Case report

A patient in his 60s, who had symptomatic persistent AF, was admitted to Beijing Anzhen Hospital in Beijing around July 2024. This patient had no prior cardiac surgery history or other diseases. Preprocedural TEE was performed to rule out LAA thrombus before radiofrequency ablation of AF. No apparent intracardiac thrombus was identified; however, the LAA structure was not visualized (Figure 1). Because the absence of visualization does not exclude thrombus formation, ² further imaging was warranted.

Figure 1.

Transesophageal echocardiographic imaging of the left atrium. Multiple views were obtained at mid-esophageal level, but the left atrial appendage could not be clearly visualized (A-D), the white arrow indicates the location of the absent of LAA. LA indicates left atrium. LAA: left atrial appendage.

Cardiac computed tomography (CCT) with three-dimensional (3D) reconstruction demonstrated moderate left atrial enlargement without thrombus and confirmed complete absence of the LAA (Figure 2), a finding rarely reported in the literature. Based on the CHA₂DS₂-VASc score, ⁵ anticoagulation therapy was continued. At the 1-year follow-up, the patient received anticoagulation therapy regularly and maintained sinus rhythm without antiarrhythmic medications and showed no related clinical symptoms. In addition, the patients have no bleeding or thromboembolism.

Figure 2.

Cardiac computed tomography of the left atrium. Left atrial anatomical characteristics were evaluated using multiplanar reconstruction axial images (A) and three-dimensional volume rendered images (B). LAA indicates left atrial appendage; RUPV: right upper pulmonary vein; LV: left ventricle; AscAo: ascending aorta; DescAo: descending aorta; PA: pulmonary artery; LAA: left atrial appendage.

Discussion

The LAA develops from the left wall of the primary atrium and lies anterolateral to the left circumflex artery, forming during the fourth week of embryogenesis. ⁶ Anatomically, the LAA is a tubular structure with variable morphology and has been described as narrow, wavy, and tubular, with a hooked apex pointing downwards but without significant age- or sex-related differences. ⁷ Functionally, current studies have shown that the LAA has the function of storing blood and contracting, which helps modulate left atrial pressure and optimize left ventricular filling. ⁸ However, in patients with AF, due to fibrillatory contraction, poor dilatation, diminished blood-flow velocities, and endocardial fibroelastosis have been observed and are regarded as predisposing factors to thrombus formation or prior history of cardiac surgery.^9,10 The hemodynamic and electrophysiological consequences of congenital LAA absence remain unclear. Some studies suggest that absence or hypoplasia of the LAA may alter atrial electromechanical properties, increasing susceptibility to AF. ¹¹ Conversely, observational studies indicate that patients undergoing LAA closure can experience improved left atrial function postoperatively. ¹²

In AF patients scheduled for ablation, preprocedural evaluation of the LAA is essential. TEE remains the first-line modality for detecting thrombus and assessing morphology, and should be performed systematically according to standardized procedures to maximize the accuracy of LAA assessment. This includes continuous scanning of sections (0°, 45°, 90°, and 135°) to ensure comprehensive visualization. ¹³ Normally, when TEE fails to demonstrate LAA structure, thrombotic occlusion should be excluded before diagnosing congenital absence. ¹⁴ CCT with multiplanar reconstruction provides valuable confirmation, enabling precise localization of the expected LAA region and differentiation from thrombotic obstruction. In particular, the smooth endocardial surface at the presumed LAA orifice on both TEE and CCT supports a diagnosis of congenital agenesis.

Thus, the importance of TEE and CCT in cardiac LAA assessment should be further emphasized. TEE is currently used most widely used and accepted modality to diagnose and exclude the LAA thrombi and the evaluation of LAA anatomy, position and function by using two-dimensional and 3D TEE. ¹⁵ TEE offers real-time evaluation of LAA anatomy and function with Doppler flow assessment. ¹⁶ Whereas CCT provides superior anatomic detail and visualization of extracardiac structures, therefore, the combination of TEE and CCT represents the most reliable diagnostic approach. ¹⁷

As this is a single case, the embryologic mechanism of LAA agenesis remains speculative. Future multicenter studies with genetic and developmental analyses are needed to clarify the underlying causes and clinical implications.

Conclusion

Congenital absence of the LAA is extremely rare; however, due to the importance of LAA in AF patients, the congenital absence of the LAA should be identified timely. Accurate diagnosis relies on the complementary use of TEE and CCT. TEE should be performed initially, followed by CCT examination with 3D reconstruction to confirm the absence and exclude secondary causes such as thrombotic occlusion.

Consent and other statements

Written informed consent for both treatment and publication was obtained from the patient. All patient-identifying information has been removed, and the figures have been fully de-identified.

The reporting of this study conforms to CARE guidelines. ¹⁸