Discussion

Congenital aneurysm of atrial appendage is a rare anomaly presenting as aneurysmal dilatation of atrial appendage without pericardium focal defect. Solitary left or right atrial appendage aneurysms have been reported. Congenital left and right atrial appendage aneurysms have been reported. Aneurysmal dilatation of the left atrial appendage was first reported in 1922.Reference Ingram and Macfie ¹ Compared with left atrial appendage aneurysm, right atrial appendage aneurysm is a rare condition that was first reported in 2001.Reference Mizui, Mori and Kuroda ² The aetiology of aneurysmal dilation of atrial appendage could be either acquired or congenital. Acquired aneurysmal dilatation of the atrial appendage is often associated with high atrial pressure resulting from stenosis or regurgitation of mitral or tricuspid valve, injury by surgeries, and so on. Congenital aneurysm of atrial appendage is associated with dysplasia of atrial pectinate muscles, bloodstream lashing, and increased atrial pressures and volume load.Reference Sevimli, Gundogdu and Aksakal ³ Left atrial appendage is usually 2–3 cm long. Left atrial appendage aneurysm can be diagnosed if its longevity is more than 3 cm. Left atrial appendage aneurysms will be regarded as “giant” when its longevity is more than 5 cm.Reference Ulucam, Muderrisoglu and Sezgin ⁴ Congenital aneurysm of atrial appendage can be diagnosed antenatallyReference Mizui, Mori and Kuroda ^{2 ,} Reference Ishii, Inamura and Kayatani ⁵ , and no family-inherited inclination has been identified.Reference Duran, Ertürk and Gündüz ⁶ Patients usually have no symptoms except that when complications appear such as development of atrial arrhythmias and systemic embolisation caused by embolus formed in the dilated left atrial appendage. Only one-third of patients developed symptoms before 10 years of age. For most patients, this condition has been discovered in the second to the fourth decades of life. Congenital aneurysm of the right atrial appendage is rare in children.Reference Mizui, Mori and Kuroda ^{2 ,} Reference Ulucam, Muderrisoglu and Sezgin ⁴

Atrial arrhythmias including atrial flutter, atrial fibrillation, and atrial tachycardia have been reported in patients with congenital aneurysm of atrial appendage, which were thought to be due to aneurysmal dilatation of atrial appendage. The exact mechanism of tachycardia was not completely understood, and two assumptions exit. One is that there might be ectopic foci in the aneurysm of the right atrial appendage with enhanced automaticity. The other is that reentrant circuit might be created by the recombination of atrial muscle fibres and fibrous tissues.Reference Mizui, Mori and Kuroda ² Owing to abnormal anatomy, these arrhythmias are usually refractory to medication therapy.Reference Scalia, Stafford and Burstow ⁷ Previous cases cured by successful resection of abnormal left atrial appendage have been reported.Reference Yildirim and Gölbaşi ^{8 ,} Reference Corti, Sciuchetti and Ferro ⁹ Clinical experience of treatment for right atrial appendage aneurysm is limited. The natural history and optimal management strategy are still unclear.Reference Gulati, Gheta and Chan ¹⁰ Mizui et alReference Mizui, Mori and Kuroda ² reported an infant with ectopic atrial tachycardia owing to an aneurysm of the right atrial appendage who developed congestive heart failure. Although successfully ablated initially, tachycardia recurred 2 days later. The right atrial appendage aneurysm was excised successfully by surgery and the patient was reversed to normal sinus rhythm thereafter. They stipulated that the reason for high recurrence rate after ablation is that the range of tissue responsible for tachycardia is too large to be completely ablated. If tachycardia is resistant to medication treatment or catheter ablation, resection of the abnormal atrial appendage might successfully eradiate the recurrent tachycardia.Reference Mizui, Mori and Kuroda ²

Characteristics of this patient were as follows: first, aneurysm of the right atrial appendage is associated with chaotic atrial tachycardia and the rapid atrial tachycardia originates from the right atrial appendage; second, arial tachyarrhythmia is refractory to medication therapy; third, radiofrequency catheter ablation is limited because of extremely thin atrial appendage wall prone to perforation. As tachycardia originates from the right atrial appendage, resection was chosen. The diagnosis of right atrial appendage aneurysm was confirmed by aneurysmal dilation of right atrial appendage and an extremely thin atrial wall observed during surgery. Pathological exploration showed generalised fibrosis, attenuation, increased adipose tissue, and severe loss of myocardial contractile protein in the right atrial appendage aneurysm that are concordant with previous literature.Reference Gulati, Gheta and Chan ¹⁰ Fourth, after resection of the right atrial appendage aneurysm, the chaotic atrial tachycardia was terminated but a new atrial tachycardia developed, which did not originate from the right atrial appendage. After 3 days of oral sotalol and propafenone oral treatment, normal sinus rhythm was regained. The patient maintained sinus rhythm within 10 months of follow up. These suggest that resection of the right atrial appendage aneurysm was effective. Finally no significant pathogenic mutations were found on all-exon high-channel gene sequencing.

Right atrial appendage aneurysm is an extremely rare congenital malformation. Potential complications include arrhythmia, thrombosis, and rupture.Reference Gulati, Gheta and Chan ¹⁰ It is refractory to the medication therapy. Resection of aneurysm is the recommended treatment with satisfactory efficacy.