Abstract Body (Do not enter title and authors here): Case
A 4-month-old female infant presented with cough and fever. A cardiac murmur was noted at the pulmonary valve area. Lab tests revealed mildly elevated WBC and CRP. CXR was unremarkable. TTE showed a markedly dilated RCA ostium (6.8 mm) and a saccular aneurysm arising from the proximal RCA communicating with the RA. Contrast-enhanced CCTA with 3D reconstruction confirmed an RCA ostial diameter of 5.5 mm, a 7 mm SNA aneurysm draining into the RA through two fistulas (2.0 mm and 2.5 mm). There were no clinical or laboratory findings suggestive of Kawasaki disease (KD). Surgical repair was performed with a right axillary thoracotomy approach. Proximal ligation of the sinoatrial nodal aneurysm (SNA) was performed, guided by an occlusion test. Postoperatively, P waves were absent on ECG on day 1 but reappeared by day 2. The postoperative course was uneventful.

Discussion
This case presents the youngest reported patient with the rare triad of a RCA aneurysm, SNA aneurysm, and dual coronary artery fistulas (CAF) draining into the RA. Previous reports are limited and exclusively involve adults. CAF is rare, with a prevalence of 0.002% in the population. Multiple fistulas are 10.7% to 16% of these cases. This case does not align with KD, the most common cause of coronary artery aneurysms (CAA) in children. Given the localization of lesions to the RCA and SNA instead of diffused coronary dilation, a congenital abnormality is the most plausible etiology.

Chronic shunting, even through a small CAF, can cause progressive dilation and aneurysm of the upstream level. In this infant, two giant aneurysms resulting from dual fistulas warranted surgical correction, even in the absence of heart failure or chamber dilation. This highlights the importance of considering aneurysm formation as a potential factor when evaluating the necessity for early intervention in infants.
This is also the first report of a right axillary thoracotomy for repairing complex coronary anomaly in infants. This approach, adopted at our center for congenital heart disease, offers excellent access to right-sided cardiac structures with benefits in recovery and cosmetic outcomes. Unlike reports of immediate P wave loss during temporary SNA occlusion, our patient retained P waves intraoperatively, suggesting age- or anatomy-related variation in sinus node perfusion.