To summarize the echocardiographic characteristics of congenital coronary artery fistula (CAF) complicated with giant coronary artery aneurysm in children and assess its utility in diagnosis and follow-up.

A retrospective study was conducted on 127 children with congenital CAF involving a single coronary artery and draining into a single cardiac chamber, who were diagnosed by echocardiography at Beijing Children's Hospital Affiliated to Capital Medical University from April 2009 to April 2025. According to the presence of giant coronary artery aneurysm or not, they were divided into a giant coronary artery aneurysm group and a non-giant coronary artery aneurysm group. Univariate analysis was used to compare baseline data between the two groups, and multivariate Logistic regression analysis was performed to identify factors associated with the development of giant coronary artery aneurysm. Postoperative echocardiographic follow-up was performed for children in the giant coronary artery aneurysm group who underwent surgery to dynamically observe the surgical outcomes.

Among the 127 children included, 49 (49/127, 38.6%) were in the giant coronary artery aneurysm group, including 23 cases (23/49, 46.9%) of right CAF. The drainage sites were the right ventricle in 28 cases (28/49, 57.1%), right atrium in 17 (17/49, 34.7%), left ventricle in 3 (3/49, 6.1%), and left atrium in 1 (1/49, 2.0%). Fourteen children (14/49, 28.6%) had other cardiac malformations. Sixteen children (16/49, 32.7%) underwent transcatheter closure or surgical treatment. The non-giant coronary artery aneurysm group consisted of 78 children (78/127, 61.4%), including 21 cases (21/78, 26.9%) of right CAF. The drainage sites were the right ventricle in 51 cases (51/78, 65.4%), left ventricle in 12 (12/78, 15.4%), right atrium in 10 (10/78, 12.8%), and left atrium in 5 (5/78, 6.4%). Twenty-nine children (29/78, 37.2%) had other cardiac malformations. None of the children in this group underwent surgical treatment. The rate of missed diagnosis or misdiagnosis in the 49 children with giant coronary artery aneurysm was approximately 12.2% (6/49). Logistic regression analysis showed that right CAF (odds ratio [OR]=0.362, 95% confidence interval [CI]: 0.162-0.810) and fistula draining into the atrium (OR=3.166, 95%CI: 1.320-7.594) were independent risk factors for the formation of giant coronary artery aneurysm. Echocardiographic findings of CAF complicated with giant coronary artery aneurysm mainly included giant aneurysmal dilation of the affected coronary artery, with no significant dilation of the contralateral coronary artery. All 16 surgically treated children showed good corrective outcomes, and no severe complications such as coronary artery stenosis were found during follow-up.

Right CAF and CAF draining into the atrium may be independent risk factors for the formation of giant coronary artery aneurysm. CAF complicated with giant coronary artery aneurysm has typical echocardiographic manifestations, and familiarity with these imaging features can reduce missed and misdiagnosis. Although the short-term benefits of surgical intervention in children are not very significant, compared with adults, it may reduce the risk of serious complications.