Discussion

Right pulmonary artery–left atrial fistula is a rare cardiovascular anomaly with right-to-left shunt. No definite embryological explanation has been described for right pulmonary artery–left atrial communication. Some have hypothesised that this anomaly may result from a communication between the right pulmonary artery and a primitive pulmonary vein and later the pulmonary vein would become incorporated into the wall of the left atrium, resulting into a fistulous connection between the right pulmonary artery and the left atrium.Reference Vadlamudi, Verma, Christopher, Penumatsa and Koneti ⁶ It often presents with central cyanosis, clubbing of fingers, exertional dyspnoea, or even systemic embolism, infective endocarditis, and cerebral abscess. Therefore, when a patient presents with these symptoms, pulmonary arteriovenous fistula should be considered. In our case, all three patients complained of cyanosis since early childhood, and all three patients had a delay in diagnosis.

Generally, chest radiography and transthoracic echocardiogram cannot confirm this diagnosis. Contrast echocardiography can detect the extent of the right-to-left shunt. CT can offer a better picture of the condition to confirm the diagnosis. Cardiac catheterisation with selective angiography is considered to be the most effective procedure for confirming this anomaly and can accurately describe the anatomical details. In our case, the abnormality was not detected on transthoracic echocardiogram and was diagnosed with CT or selective pulmonary artery angiography. In cases 1 and 2, angiography was performed to confirm the direct communication between the proximal right lower pulmonary artery and the left atrium.

Surgical closure is a traditional treatment for fistulas, as in cases 2 and 3, especially large ones; however, transcatheter closure of the fistula can also be a good option in most cases. Some authors have reported using an Amplatzer duct occluder,Reference Vadlamudi, Verma, Christopher, Penumatsa and Koneti ⁶ Amplatzer septal occluder,Reference Ergul, Nisli and Aydogan ⁵ muscular ventricular septal occluder,Reference Ding, Xu, Liu, Yan and Qin ⁷ or coilsReference Slack, Jedeikin and Jones ⁹ to treat fistulas. Rarity of the disease, a certain rate of missed diagnosis, morphology of the fistula, and fear of embolisation directly into the left atrium are some of the possible reasons for the rarity of interventional treatment. Generally, device choice depends on the size of the vessel, the anatomy of the narrowing, and also the experience of operators. The retrograde deployment from the left atrial side is a method using a duct occluder device in the presence of an atrial septal defect or patent foramen ovaleReference Ece, Uner, Cuce and Balli ¹⁰ or by trans-septal puncture. In the absence of an atrial septal defect or patent foramen ovale, however, double-disc devices may be used such as ventricular septal occluder, Amplatzer septal occluder,Reference Ece, Uner, Cuce and Balli ¹⁰ or vascular plug device. Coils are only suitable for right pulmonary artery–left atrial fistulas with a narrow neck, and not for large ones. Duct occluders with a larger disc on the distal end are not ideally suited for closing fistulas from the pulmonary arterial approach because of the possibility of displacement and systemic embolism. In case 1, we chose a Duct occluder and implanted the device from the pulmonary arterial site and obtained good results; however, this is not recommended, because it cannot be released as distally as possible to prevent distal right pulmonary artery obstruction, and needs larger devices. In conclusion, transcatheter closure of right pulmonary artery–left atrial fistula appears to be a good alternative choice.