RPA-LA fistula is one of the rare congenital anomalies causing silent cyanosis. There are four types of RPA-LA fistulas described. Type I: RPA branches normally, with an additional fistulous channel connecting RPA and LA. Pulmonary venous return is normal. Type II: The lower lobe branch of the RPA drains directly into the LA, forming an aneurysmal sac in the absence of the right lower pulmonary vein. Type III: All right- and left-sided pulmonary veins drain into the abnormal channel that connects RPA and LA. Type IV: Right-sided pulmonary veins entering the aneurysmal sac of the RPA LA fistula with normal left-sided pulmonary venous drainage to the left atrium (Fig. 3) [2, 3].

Types of RPA-LA fistula—schematic representation: Type I: proximal RPA-LA fistula with normal pulmonary venous drainage. Type II: Lower lobe branch of RPA forms an aneurysmal sac and connects to LA in the absence of the right inferior pulmonary vein. Type III: The aneurysmal fistula tract receives all the pulmonary venous drainage. Type IV: All right-sided pulmonary veins drain into the aneurysmal sac, with normal left-sided pulmonary venous drainage to LA (LA left atrium, LLPV left lower pulmonary vein, LPA left pulmonary artery, LUPV left upper pulmonary vein, PA pulmonary artery, RA right atrium, RLPV right lower pulmonary vein, RMPV right middle pulmonary vein, RUPV right upper pulmonary vein)

In an otherwise structurally normal heart, the bubble contrast echo gives a clue to detect this right-to-left shunt. CT and cardiac catheterization studies will be helpful for confirmation. In our case, the echocardiogram and bubble contrast study itself well delineated the additional fistula tract from the proximal RPA to LA with normal pulmonary venous drainage, suggesting a type I RPA-LA fistula. Cardiac CT and Catheter angiography were used for confirmation and to measure the tract opening precisely for the selection of the appropriate device.

Surgical repair was the preferred mode of management until the first transcatheter coil closure of the RPA-LA fistula was reported by Slack et al. in a sick neonate [4]. Further modifications by using various devices like duct occluders, septal closure devices, and vascular plugs were reported. Francis et al. used a 12 × 14 Amplatzer duct occluder in a 12-year-old child through the atrial septal defect after forming a veno-venous loop, as in our case [5]. Vadlamudi et al. reported a similar case successfully closed with an 18 × 20 duct occluder after a transseptal puncture [6]. Our case might be the one that used the largest duct occluder based on the available literature search to date. Kumar et al. reported a 28-year-old adult patient with an RPA-LA fistula tract closed with a vascular plug [7]. Antegrade deployment of double-disc devices from the RPA to the fistula is an alternate option. However, there is a high risk of RPA occlusion in the pediatric population if it is not deployed properly via the antegrade approach, which is comparatively less common in the transseptal approach. Closure of an RPA-LA fistula with a muscular septal occluder device via an antegrade approach in an adult patient was reported by Ding et al. [8].

Location, size, and tortuosity are important determinants of amenability for device closure. Precise measurement and appropriate device selection are important. Duct occluders, muscular septal closure devices, and vascular plug devices have been used for percutaneous closure. A transseptal approach with a veno-venous loop is the preferred route for device deployment in the pediatric population, especially with a single disc duct occluder. Antegrade approach: closing the fistula from the venous end without looping (Right ventricle → main pulmonary artery → RPA → Fistula) is an alternative, but a double disc device should be used; however, the improper position may compromise distal RPA flow.