Discussion

Transposition of the great arteries is one of the most common cyanotic heart malformations, accounting for 5–7% of CHDs. It is well tolerated haemodynamically in the prenatal period, because of foetal shunts: the foramen ovale and the ductus arteriosus. After birth, the situation changes dramatically, as two separate parallel blood circuits are created, which is incompatible with life.^{Reference Wernovsky, Allen, Driscoll, Shaddy and Feltes1}

The current management of newborns with transposition of the great arteries includes the prostaglandin E1 infusion for ductal patency, and, if needed, restoring adequate flow at the level of interatrial septum with balloon atrioseptostomy procedure. These interventions usually allow the stabilisation of the newborn’s condition until the corrective operation.^{Reference Wernovsky, Allen, Driscoll, Shaddy and Feltes1}

There is, however, a small subgroup of patients with transposition who, despite prostaglandin infusion and adequate-sized interatrial communication, develop intractable hypoxemia, acidosis, and often die pre-operatively.^{Reference Karimi, Kirshbom, Kopf, Steele and Sullivan2} This phenomenon is attributed to persistent pulmonary hypertension of the newborn, defined as failure of normal pulmonary vascular resistance to fall after birth and usually presenting with varying degrees of respiratory failure.^{Reference Mathew and Lakshminrusimha3} In newborns with transposition of the great arteries, persistent pulmonary hypertension, especially with restrictive interatrial communication, is deemed a critical combination.^{Reference Karimi, Kirshbom, Kopf, Steele and Sullivan2,Reference Roofthooft, Bergman, Waterbolk, Ebels, Bartelds and Berger4} Management strategies of these patients include balloon atrioseptostomy, administration of pulmonary vasodilators, and extracorporeal membrane oxygenation in refractory cases, in addition to the appropriate ventilation, sedation, and inotropic support.^{Reference Roofthooft, Bergman, Waterbolk, Ebels, Bartelds and Berger4} The data on extracorporeal membrane oxygenation use in either pre- or post-operative period are not extensive; however, they show a possibility to stabilise the patient until the corrective surgery and reverse the pulmonary hypertension in some cases. Still, the mortality among patients requiring extracorporeal membrane oxygenation remains the highest. Timing of arterial switch operation is controversial, and some authors suggest early surgery with post-operative extracorporeal membrane oxygenation support as a preferred option.^{Reference Sallaam, Natarajan and Aggarwal5}

The pathophysiology of persistent pulmonary hypertension in newborns with transposition is complex and not yet fully understood. It is suggested that the prenatal restriction of the ductus arteriosus increasing the pulmonary blood flow may lead to anatomical changes in pulmonary arterioles, which were demonstrated in histological studies.^{Reference Maeno, Kamenir, Sinclair, van der Velde, Smallhorn and Hornberger6,Reference Kumar, Taylor, Sandor and Patterson7} Prenatal ductal constriction has long been related to maternal intake of non-steroidal anti-inflammatory drugs in the third trimester of pregnancy, which inhibit the prostaglandin synthesis pathway. However, there is a growing area of evidence that many other substances, especially polyphenol-rich foods and potentially corticosteroids, may have a similar effect. The pathophysiologic mechanisms are yet to be elucidated; however, disruption of arachidonic acid signalling and modulating effect on ductal wall reactivity to different stimuli are implied.^{Reference Zielinsky and Busato8} This fact is of great clinical importance, since corticosteroids are often used in threatened pre-term labour, and many foods generally considered as healthy (e.g., green tea, oranges, grapes, berries) are rich in polyphenols.

In our patient, the reason for ductal closure was unclear; however, since there was no history of exposure to non-steroidal anti-inflammatory drugs or polyphenol-rich food, prophylactic steroid course seemed the most probable factor. There is no existing data on the influence of atosiban on the ductus arteriosus,⁹ and therefore, we cannot exclude its co-effect – it should be subject to further research. In the literature, we found just one description of complete closure of the ductus arteriosus in a foetus with transposition, also with no apparent cause.^{Reference Donofrio10}