Discussion

Tricuspid atresia occurs infrequently, with a prevalence of 0.3–3.7% in patients with CHD.Reference Fyler ¹ Aortopulmonary window is rarer still, being found in no more than 0.2% of patients with CHD.Reference Jacobs, Quintessenza, Gaynor, Burke and Mavroudis ² Coexistence of these anomalies in the same patient is extremely rare. To our knowledge, there have been only three reports of such cases in the literature.Reference Geva, Ott, Ludomirsky, Argyle and O’Laughlin ^{3 –} Reference Hauck, da Cruz, Jaggers and Jone ⁵ Given the extreme rarity of this condition, it is clear that there are no established treatment guidelines. Geva et alReference Geva, Ott, Ludomirsky, Argyle and O’Laughlin ³ have described the case of type IB tricuspid atresia – normally related great arteries with pulmonary stenosis and hypoplasia – with an aortopulmonary window that was palliated with the closure of the aortopulmonary window using a fenestrated patch. The case of Peer et alReference Peer, Donofrio, Gaur and Sinha ⁴ reported similar morphology and underwent ligation of the aortopulmonary window, followed by placement of a 3.5-mm modified Blalock–Taussig shunt because of decreased pulmonary blood flow as a second operation, and, finally, creation of a superior cavopulmonary anastomosis as a third procedure. The patient described by Hauck et alReference Hauck, da Cruz, Jaggers and Jone ⁵ with type IIA tricuspid atresia – malposed great arteries with pulmonary atresia – and an aortopulmonary window was initially palliated by separation of the pulmonary artery from the aorta, atrial septectomy, and placement of a 3.5-mm modified Blalock–Taussig shunt as a first surgical procedure. This was followed by bidirectional cavopulmonary anastomosis as a second operation.

Patients with tricuspid atresia and normally related great vessels can have increased, balanced, or reduced pulmonary blood flow depending upon the size of the ventricular septal defect and/or the extent of pulmonary stenosis. In our case, pulmonary over-circulation was initially thought to be due to the presence of a non-restrictive ventricular septal defect and due to the absence of any pulmonary stenosis. Establishing an accurate diagnosis with echocardiography alone can be challenging, as also reported by Hauck et al.Reference Hauck, da Cruz, Jaggers and Jone ⁵ Physiological neonatal pulmonary hypertension initially causes the shunt at the level of the aortopulmonary window to be less prominent, thus reducing the chances of visualising the aortopulmonary window on the initial echocardiogram. With the physiological drop in pulmonary vascular resistance, the clinical signs and echocardiographic findings consistent with an aortopulmonary window became more obvious.

As far as we are aware, this is the first described case of tricuspid atresia and aortopulmonary window with pulmonary over-circulation due to not only the aortopulmonary window but also the lack of pulmonary stenosis at any level. All other reported cases had some degree of restriction of antegrade pulmonary blood flow due to a restrictive VSD, pulmonary stenosis, or pulmonary atresia.

Achieving a balanced pulmonary circulation in the treatment of these patients, as described by Peer et al,Reference Peer, Donofrio, Gaur and Sinha ⁴ can be quite challenging. At the time of repair of the aortopulmonary window, we decided to totally eliminate antegrade pulmonary blood flow and to leave the patient’s pulmonary blood flow shunt dependent. We felt that this approach was more predictable and reproducible than placing either an extraluminal or an intraluminal pulmonary artery band in the presence of the pulmonary artery patch angioplasty performed as part of the repair of the aortopulmonary window, although it was controversial. Partial closure of the aortopulmonary window with a fenestrated patch, as reported by Geva et al,Reference Geva, Ott, Ludomirsky, Argyle and O’Laughlin ³ is a less-predictable way to control pulmonary blood flow, seems more likely to produce pulmonary artery distortion over time, and will ultimately require definitive repair. Therefore, a full separation of the aorta from the pulmonary artery, with patch augmentation of both, in combination with placement of a systemic-to-pulmonary artery shunt seems to the best surgical approach for this condition.

In conclusion, tricuspid atresia type IC with aortopulmonary window is very rare. Its clinical signs and echocardiographic diagnosis can be less obvious in young neonates. We advocate full separation of the aorta from the pulmonary artery, with patch angioplasty of both, and placement of a systemic-to-pulmonary artery shunt as the initial surgical approach to ultimate Fontan palliation.