Growth-retarded infants, or those born very prematurely, with structural cardiac disease have a poor prognosis.1–3 In such infants, there is little published about the optimal time for cardiac surgery. Timing of delivery is also contentious if the defect has been diagnosed antenatally, and there is restriction of fetal growth.
Case report
Isolated fetal cardiac asymmetry was noted at the routine scan carried out at 21 weeks for detection of fetal anomalies in a 34-year-old mother considered at low risk. Specialist fetal echocardiography at 23-week gestation suggested a diagnosis of tetralogy of Fallot with pulmonary atresia, which was confirmed on a further scan made at 30-week gestation. Preparations were made for local delivery at term, anticipating postnatal infusion of prostaglandin and early transfer to the tertiary centre for construction of a Blalock–Taussig shunt.
An emergency caesarean section was performed at 31-week gestation because of deteriorating cardiotocographic findings associated with slowing of growth and oligo-hydramnios. The female infant weighed 983 grams at birth, and required no resuscitation. Although she was breathing spontaneously, she was electively intubated and ventilated in view of her prematurity and weight. An infusion of prostaglandin E1 was commenced at 10 nanograms per kilogram per minute. She maintained an adequate blood pressure, and arterial oxygen saturations were measured above 80 per cent in air. Postnatal echocardiography confirmed tetralogy of Fallot with pulmonary atresia. After reviewing the echocardiogram, the cardiologists, cardiothoracic surgeons, and neonatologists together decided to pursue conservative treatment with continued infusion of prostaglandin and ventilation whilst awaiting growth. Surgical intervention was planned at a weight of approximately 2 kilograms, but sooner if her condition should deteriorate.
Total parental nutrition was commenced on the third day of life. In view of her growth retardation and risk of necrotising enterocolitis, enteral feeding via a nasogastric tube was introduced slowly to a maximum of 100 millilitres per kilogram per day. Excellent growth was achieved with total fluids of 200 millilitres per kilogram per day, the fluids comprising 12.5 per cent dextrose total parental nutrition with 3.5 grams intralipid. Ductal patency was maintained with an infusion of prostaglandin at a rate of 5 nanograms per kilogram per minute, delivered via a long line together with the total parental nutrition. She was ventilated in air until the 30th day of life, and then maintained on nasal continuous positive airway pressure with increasing time off respiratory support.
She remained on the regional neonatal intensive care unit until the 66th day, when she was transferred for cardiac surgery weighing 2.8 kilograms. A modified Blalock–Taussig shunt of 3.5 millimetres diameter was constructed, and her patent arterial duct was ligated. Complete surgical correction was performed at 8 months. At a corrected age of 18 months, she is developing normally, with all parameters for growth following the third centile.
Discussion
The incidence of cardiac disease in premature infants born with low weight is similar to those born at term and appropriately grown.1, 2 With congenital lesions other than a ventricular septal defect, mortality in infants weighing less than 1 kilogram has been reported as 82 per cent. Construction of a palliative shunt in those weighing less than 2 kilograms has been considered a predictor of early mortality.4
Infusions of prostaglandin are now regularly used in neonates born at term with duct-dependent cardiac lesions, serving to facilitate transfer and stabilisation prior to cardiac surgery. In our patient, the prolonged infusion of prostaglandin allowed development of the immature lungs and brain, and also generalised growth of the child. At a weight of over 2 kilograms, the risks and technical difficulties of construction of the shunt were very much reduced.
The gains of delaying surgery were balanced against other problems, such as sepsis, necrotising enterocolitis, acute renal failure, and ventilator dependency with chronic lung disease. The infusion of prostaglandin may cause respiratory depression, cutaneous dilatation, and temperature elevation. As far as we are aware, there are no studies comparing immediate operative palliation by construction of a shunt to use of an infusion of prostaglandin in such infants born at low weight. In cases where corrective surgery is indicated, the minimum weight at which surgery becomes technically and safely possible remains controversial. Chang et al.5 reported improved survival with early surgery in infants weighing less than 2,500 grams, but there was a higher mortality for infants under 1,500 grams, and the smallest infant in their series weighed 1,050 grams. Successful surgical correction has been performed in infants weighing as little as 700 grams,6 but experience in these very small neonates is limited, with little information on long-term survival and neurodevelopmental outcome. Ligation of the persistently patent arterial duct in infants born at extremely low weight is reported to carry a surgical mortality of 10 per cent.7
Our patient, therefore, highlights the dilemmas in determining optimal timing for delivery, and for subsequent surgical intervention, in babies diagnosed antenatally with complex cardiac malformations who suffer retardation of their growth. Recent data suggests that premature delivery in babies with such diseases diagnosed prenatally is associated with a poor outcome, with weight at birth being the most important factor determining risk.7 Antenatal diagnosis in this case permitted optimisation of management. Given the prematurity and weight of the infant, it was most appropriate that initial care occurred on a regional unit for neonatal intensive care, with staff that were used to dealing with these problems. With local cardiac expertise, and an agreed plan for management, a stay of 2 months in a cardiac intensive care unit was avoided, thereby reducing the pressure on specialist cardiac beds and decreasing cancellations for cardiac surgery, the latter now being a significant factor in the United Kingdom. In our opinion, prolonged medical therapy with prostaglandin, and careful communication between neonatologists and cardiologists, resulted in a successful outcome for our patient, although we recognise that our strategy was by no means devoid of risk.
