Abstract 2452: Percutaneous Stenting of the Atrial Septum in Fetal Lambs
Introduction: HLHS with a severely restrictive pfo has a neonatal mortality of 50 –70 %. Survivors have a high mortality after a bidirectional Glenn due to high PVR and abnormal lung lymphatics from fetal LA hypertension. The very high mortality has led to fetal interventions to open the atrial septum. Attempts with static balloon dilation or septostomy have been disappointing due to the small atrial hole produced. Stenting the atrial septum may lead to a larger more reliable atrial communication, and this was attempted in normal fetal lambs.
Methods: 13 fetuses (16 –20 weeks gestation) in 12 pregnant anesthetised ewes were studied. A strictly percutaneous approach without a laporotomy/uterine exteriorisation was used. Four methods were tried:
Transpulmonary access (7F sheath,18G needle),3 fetuses all prone. This route requires entry into the high IVC close to the IVC-RA junction. Septum primum is pierced with the 18G needle.
Transhepatic access (4F sheath, 4F catheters), 2 fetuses all supine. This route allows entry lower in the IVC, but needs shaped catheters to engage the septum primum.
Transpulmonary access (4F sheath, 18G needle), 4 fetuses all prone.
Transpulmonary access (18G needle), 4 fetuses all prone.
Results: Coronary stents (2–5mm) were implanted in the septum primum n=10) and one 7mm stent was placed in a pfo. A supine fetal lie (n=2) prevented stenting in this non-exteriorised uterus model. Three fetuses were made prone by external version. Important right hemothorax due to IVC injury occured in seven. Coil delivery across the IVC entry site did not stop the bleeding from 7F sheaths. Multiple IVC entries were made with a 4F sheath without bleeding, which if present was due to retraction of a 5mm balloon across the IVC after stent delivery. One fetus (4F sheath, 5mm stent) was resuscitated by drainage of a haemothorax, but spontaneously aborted 5 days later. Delivery of smaller coronary stents (2–2.5mm) by 18G needles did not lead to acute haemothorax and all were alive >48hrs post-procedure.Stent embolisation had occurred in one (2 mm stent).
Conclusion: Small coronary stents expandable to almost 3mm can be safely delivered into the septum primum.The 4F system can be optimized further to allow deployment of 5mm stents.