MRCS-0301

An infant, 5 weeks and 6 days old born with a large sub-aortic ventricular septal defect, is prepared for pulmonary artery banding through a left thoracotomy (the child is not fit for a surgical closure). The surgeon initially passes his index finger immediately behind two great arteries in the pericardial sac to mobilise the great arteries in order to pass the tape around the pulmonary artery. Into which space is the surgeon’s finger inserted?