Percutaneous ultrasound‐guided stenting of the atrial septum in fetal sheep

Abstract

Hypoplastic left heart syndrome (HLHS) with a restricitive foramen ovale is associated with high mortality related to fetal left atrial hypertension. Fetal atrial balloon septoplasty has largely failed to achieve adequate decompression due to the small size of the holes produced. We attempted to produce larger atrial communications by stenting the atrial septum in fetal sheep using a minimally invasive technique. We used a percutaneous, ultrasound-guided transpulmonary or transhepatic approach to attempt deployment of coronary stents (2-5 mm in diameter and 13-23 mm in length) in the atrial septum primum of 10 normal fetal sheep. Coronary stents were deployed in eight of the 10 fetal sheep (119-139 days' gestation). The transhepatic route was unsuccessful (n = 2). Transpulmonary implantation was only possible in prone fetuses, so three initially supine fetuses underwent external version. Small coronary stents (2.0-2.5 mm in diameter) were deployed rapidly without complication via an 18G needle (n = 4). Larger coronary stents (5 mm in diameter) were delivered through a 4F sheath, but a right pleural effusion occurred in three of the four cases, related to inferior vena cava injury by the balloon. One stent dislodged from a floppy septum. Another was partially occluded within a week by endocardial cells. Percutaneous ultrasound-guided deployment of coronary stents into the septum primum is feasible without laparotomy or uterine exteriorization in fetal sheep. Partial luminal occlusion by rapid proliferation of endocardial cells is a concern.