Juxtaposition of the atrial appendages is an extremely rare congenital cardiac malformation. It is usually discovered incidentally during autopsy or surgery. This report aims to increase awareness of right juxtaposition of the left atrial appendage. We report a Chinese Han female aged 2 years and 10 months with recurrent lung infections after birth, who was diagnosed with congenital heart disease, corrected transposition of the great arteries, ventricular septal defect, and arterial ductus arteriosus at the local hospital and improved after the pulmonary artery banding procedure. The patient presented to our hospital with intermittent cough. During preoperative evaluation, a review of imaging data revealed a right juxtaposition of the left atrial appendage on enhanced computed tomography. Right juxtaposition of the left atrial appendage is a rare congenital heart anomaly that often occurs in conjunction with complex cardiac malformations. Diagnosis requires a combination of imaging modalities to improve detection rates. Careful identification of cardiac structures during surgery is crucial, as alterations in cardiac anatomy may increase surgical risks. For instance, the opening of juxtaposed atrial appendages could be mistaken for an atrial septal defect.

Juxtaposition of the atrial appendages is known to occur in specific congenital heart lesions. Recognition of these variants is critical in balloon atrial septostomy and atrial switch operations. There remains little clinical data on the prevalence and associations of these lesions. This is the largest echocardiographic study of juxtaposition of the atrial appendages. This is a retrospective study using the Mt. Sinai echocardiogram database (EchoLAN), which contains echocardiogram reports performed or reviewed at Mt. Sinai Hospital (New York, NY) between 1992 and 2019. Each report was reviewed for associated intracardiac and extracardiac anomalies and the prevalence of juxtaposed atrial appendage among specific diagnosis, including tricuspid atresia, transposition of the great arteries, and double outlet right ventricle, was calculated. Descriptive and analytical statistics were performed as applicable, including Fisher's exact test, with p value < 0.05 considered statistically significant. Forty-nine patients had juxtaposed atrial appendages (1.2/1000 patients): Thirty-eight had LJRAA (0.9 per 1000 patients) and eleven had RJLAA (0.3 per 1000 patients). LJRAA was seen in 22% of tricuspid atresia, 6% of d-TGA, 1% of l-TGA, and 5% of DORV. RJLAA was seen in 2% of DORV, and none of the other lesions. Of associated lesions, dextrocardia, mesocardia, transposition, tricuspid atresia, double inlet left ventricle, and pulmonary valve stenosis were more likely to be present in LJRAA, while bicuspid aortic valve and left ventricular hypoplasia were more likely to be present in RJLAA. This study reaffirms our understanding of juxtaposition of the atrial appendages, its prevalence, and clinical importance.

A 40-year-old woman underwent an atrial septal defect closure 4 years before presentation. During the operation, juxtaposition of the atrial appendages was found simultaneously but no obvious communication was found between the appendages. She recently experienced desaturation on exercise, and the residual communication was found between the juxtaposed atrial appendages. The residual communication was closed from the right to the left atrium. Herein, we report the rare case of juxtaposition of the atrial appendages with residual communication between them after an atrial septal defect closure.

Although many anatomical variations may be encountered in children with double outlet right ventricle, coexistence of levo-malposed great vessels and left juxtaposed atrial appendages is uncommonly observed. This case report underlines the rarity of this anatomical combination and its clinical significance along with the surgical management in an infant.