Background Diagnosis of coarctation can be notoriously difficult. In the presence patent ductus arteriosus (PDA), classical signs of coarctation may not be seen on the echocardiogram. Big right ventricle should arouse the suspicion of evolving coarctation of aorta.

Case report A full term baby with severe IUGR was found to have borderline low oxygen saturations with no difference in pre and post ductal sats. Baby had normal femoral pulses and there was no heart murmur. When baby was seen at tertiary paediatric cardiology centre, echocardiogram showed big right ventricle with PFO/ASD, small VSD, large PDA and bicuspid aortic valves.

Baby was closely monitored for the evolving coarctation at the tertiary neonatal unit. Within 12 h of the paediatric cardiology review this baby collapsed suddenly. PDA must have closed suddenly and commonly used small dose of Prostin was ineffective. Despite the appropriate monitoring and resuscitation, unfortunately, this baby could not be saved as deterioration was so rapid.

Discussion and learning points (1) Big right ventricle on the antenatal and postnatal echocardiogram can be a normal finding but may be pathological. It should arouse suspicious of evolving coarctation of aorta. Other rare causes include left ventricular outflow tract obstruction, hypoplastic left ventricle, double outlet ventricle, TAPVC and AV malformation. (2) Ductus arteriosus can close suddenly (fortunately very rarely!). (3) In collapsed patients with suspicion of coarctation of aorta we should start a much higher (50–100 ng/kg/min) dose of Prostin. Much higher doses have been used in discussion with the paediatric cardiologist.