New device permitting non-invasive reversal of fetoscopic tracheal occlusion: ex-vivo and in-vivo study.Ultrasound Obstet Gynecol. 2020 Jun 30 [Online ahead of print]UO
One of the drawbacks of fetoscopic endoluminal tracheal occlusion for congenital diaphragmatic hernia is the need for a second invasive intervention to reestablish airway patency. The "Smart-TO" (Strasbourg University-BSMTI, France) is a new balloon for endoluminal tracheal occlusion, which spontaneously deflates when placed in a strong magnetic field, therefore overcoming the need of a second procedure. The safety and efficacy of this device has not been demonstrated. This study investigates the reversibility, local side effects, and occlusiveness of the Smart-TO both in a simulated in-utero environment as well as in the fetal lamb model.
First, reversibility was tested in a high-fidelity simulator. Following videoscopic tracheoscopic balloon insertion, the mannequin was placed within a 1L water-filled balloon to mimic the amniotic cavity. This was held by an operator in front of the abdomen in different fetal and maternal positions to mimic the most common clinical scenarios. Following exposure to the magnetic field generated by a 1.5T magnetic resonance (MR) machine, deflation was assessed by tracheoscopy. In case of failed deflation, the mannequin was reinserted into a water-filled balloon for additional MR exposure, up to maximum three times. Secondly, reversibility, occlusiveness, and local effects were tested in-vivo in fetal lambs. Tracheal occlusion was performed in fetal lambs on gestational day (GD) 95 (term=145), either with the balloon currently clinically used (Goldbal2, Balt, Montmorency, France) (n=5) or the Smart-TO balloon (n=5). On GD116, the presence of the balloon was assessed by tracheoscopy. Deflation was performed by puncture (Goldbal2) or by MR exposure (Smart-TO). Six unoccluded lambs served as controls. Following euthanasia, the lung-to-body-weight-ratio, lung morphometry, and tracheal circumference were assessed. Local tracheal changes were measured using a hierarchical histologic scoring system.
Ex-vivo, balloon deflation occurred after a single MR exposure in 100% of cases in standing position with the mannequin at 95 (n=32), 55 (n=8), and 125 (n=8) cm height. The deflation rate at first exposure was 100% when lying on a stretcher (n=8). Three out of eight balloons (37.5%) failed to deflate at first exposure when sitting in a wheelchair. Of these, two balloons deflated after a second exposure. One balloon remained inflated after a third exposure. In-vivo, all Smart-TO balloons deflated successfully. The LBWR was significantly higher than controls and comparable for the two balloon types. There were no differences in lung morphometry and tracheal circumference. Tracheal histology showed minimal changes for both balloons.
The Smart-TO balloon was effectively deflated by exposure of the fetus in different positions to a 1.5T-MR system. There was only one failure, i.e., when the mother was sitting in a wheelchair. In healthy fetal lambs, the balloon is as occlusive as the clinical standard Goldbal2 system and has only limited local side effects. This article is protected by copyright. All rights reserved.